WO2018093332A1

WO2018093332A1 - Multi-material ratchet-like mechanism

Info

Publication number: WO2018093332A1
Application number: PCT/SG2017/050571
Authority: WO
Inventors: Sawako KAIJIMA; Martin DUNN; Tat Lin LEE; Amirhosein SAKHAEI
Original assignee: Singapore University Of Technology And Design
Priority date: 2016-11-16
Filing date: 2017-11-16
Publication date: 2018-05-24

Abstract

A multi-material ratchet-like mechanism including a first body interfacing a second body. The multi-material ratchet-like mechanism may include a first interlocking element which may be a continuous structure extending from a portion of the first body and which includes a first compliant mechanism between the portion of the first body and a tip portion of the first interlocking element. The interlocking joint may further include a second interlocking element extending from a corresponding portion of the second body and having a corresponding tip portion. The tip portion of the first interlocking element may be configured to cause elastic deformation of the first compliant mechanism so as to slide the respective tip portions over each other when engaging in the first direction, and further configured to lock when engaging in the second direction. The first compliant mechanism and the tip portion of the first interlocking element may be of different materials.

Description

MULTI-MATERIAL RATCHET-LIKE MECHANISM

Cross-reference to Related Applications [0001] The present application claims the benefit of the Singapore patent application No. 10201609618V filed on 16 November 2016, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

[0002] Embodiments generally relate to a multi-material ratchet-like mechanism and, more particularly, relate to a multi-material ratchet-like mechanism including a first body interfacing with a second body such that the first body and the second body are movable relative to each other in a first direction and are prevented from relative movement in a second direction.

Background

[0003] The conventional ratchet mechanism is a classical mechanism in mechanical engineering which limits either rotary or linear motion to only one direction. Typically, the conventional ratchet mechanism is composed of pawl and gear with asymmetric teeth geometry at the contact area that allows a sliding motion in one direction and a locking behaviour on the opposite direction. Typically, the gear includes uniform asymmetrical teeth at its perimeter. For example, the geometry of the tooth can include a steep slope near perpendicular to the gear motion on one side while the other side has a gradual slope. Further, the pawl is usually positioned next to the gear and is in contact with the gear teeth. The pawl will slide over the gear teeth in one direction while resisting the reverse motion by coming into contact with the steep edge of the gear tooth. The pawl usually moves near perpendicular to the gear motion and is usually equipped with a biasing or spring system to apply force to the pawl in order to maintain contact with the teeth. Both the gear and pawl are typically mounted to a common base so as to keep the disposition of the gear and pawl relatively fixed with respect to each other during operation. The above classical ratchet mechanism has been applied to various everyday objects such as bicycle conveyor belts, zip ties, wrenches as well as to more complex system of overrunning clutches and turnstiles.

[0004] Typically, such conventional ratchet mechanism is constructed from a homogeneous stiff material. The pawl of the conventional ratchet mechanism is also typically connected to a multi-components biasing mechanism to facilitate movement of the pawl for interacting with the gear. Further, the conventional ratchet mechanism would require a substantial space relative to the tooth size for either pawl or gear to move near perpendicular to the ratchet motion during the slide insertion. This perpendicular motion is generally controlled by an extra component such as a multi- components biasing mechanism or a spring mechanism. Hence, direct application of the conventional ratchet, for example in a sliding interlocking joint, would be challenging as there would be a need to accommodate the near perpendicular motion/space required around the conventional ratchet mechanism as well as to factor in the multi-components biasing mechanism or the spring mechanism.

Summary

[0005] According to various embodiments, there is provided a multi-material ratchet-like mechanism including a first body and a second body interfacing with the first body. The multi-material ratchet-like mechanism may further include a first interlocking element which extends from a portion of the first body and which includes a first compliant mechanism between the portion of the first body and a tip portion of the first interlocking element. The multi-material ratchet-like mechanism may further include a second interlocking element which extends from a corresponding portion of the second body and which includes a corresponding tip portion. The tip portion of the first interlocking element may be configured to cause elastic deformation of the first compliant mechanisms so as to slide the tip portion of the first interlocking element over the corresponding tip portion of the second interlocking element when engaging in the first direction. The tip portion of the first interlocking element may be further configured to lock against the corresponding tip portion of the second interlocking element when engaging in the second direction. The first interlocking element may be a continuous structure. The first compliant mechanism and the tip portion of the first interlocking element may be made of different materials. [0006] According to various embodiments, the second interlocking element may include a second compliant mechanism between the corresponding portion of the second body and the corresponding tip portion of the second interlocking element. The second interlocking element may also be a continuous structure. The second compliant mechanism and the tip portion of the second interlocking element may also be made of different materials. According to various embodiments, the corresponding tip portion of the second interlocking element may be configured to cause elastic deformation of the second compliant mechanism when engaging the tip portion of the first interlocking element in the first direction. The corresponding tip portion of the second interlocking element may be further configured to lock against the tip portion of the first interlocking element when engaging in the second direction.

Brief description of the drawings [0007] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

FIG. 1 shows an interlocking element of a body of a multi-material ratchet-like mechanism according to various embodiments;

FIG. 2A to FIG. 2D illustrate a multi-material ratchet-like mechanism according to various embodiments;

FIG. 3 shows a body of a multi-material ratchet-like mechanism according to various embodiments;

FIG. 4A and FIG. 4B show an unassembled view and an assembled view of an interlocking joint according to various embodiments;

FIG. 5 shows an experimental setup using male and female jigs according to various embodiments;

FIG. 6 shows a summary of an analysis of the mechanical behaviour of one embodiment of the multi-material ratchet-like mechanism during the insertion process by finite element simulation and physical experiments; FIG. 7 shows a summary of an analysis of the mechanical behaviour of one embodiment of the multi-material ratchet-like mechanism in the locking mode by finite element simulation and physical experiments;

FIG. 8 shows results of a parametric study conducted by varying the elastic modulus of the flexible region to determine its effect on maximum reaction force during insertion and locking processes;

FIG. 9 shows the results of a parametric study showing the relationship between the reaction forces to the geometric parameters; and

FIG. 10 shows the schematic of connection and comparison of force- displacement behaviour of a single configuration and array configuration.

Detailed description

[0008] Embodiments described below in context of the apparatus are analogously valid for the respective methods, and vice versa. Furthermore, it will be understood that the embodiments described below may be combined, for example, a part of one embodiment may be combined with a part of another embodiment.

[0009] It should be understood that the terms "on", "over", "top", "bottom", "down", "side", "back", "left", "right", "front", "lateral", "side", "up", "down" etc., when used in the following description are used for convenience and to aid understanding of relative positions or directions, and not intended to limit the orientation of any device, or structure or any part of any device or structure. In addition, the singular terms "a", "an", and "the" include plural references unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise.

[00010] Various embodiments of a multi-material ratchet-like mechanism, more particularly, a multi-material ratchet-like mechanism that includes a first body interfacing with a second body such that the first body and the second body are movable relative to each other in a first direction and are prevented from relative movement in a second direction, have been provided to address at least some of the issues identified earlier. According to various embodiments, the multi-material ratchet-like mechanism may be applied to a device or apparatus or machinery or tool which requires ratchet-like behaviour or motion, or an interlocking joint or assembly. [00011] Various embodiments have been provided to enable the elimination of springs and global movement of the pawl or gear that typically exist in classical ratchets. Thus, allowing easy assembly and implementation in different applications.

[00012] According to various embodiments, the multi-material ratchet-like mechanism may have integrated the classical ratchet mechanism and multi-material compliant mechanism. The compliant/flexible materials of the multi-material compliant mechanism of the multi-material ratchet-like mechanism may tolerate large deformation while the ratchet-like geometry of the tooth tip of the multi-material ratchet- like mechanism may allow locking of the respective components. Accordingly, various embodiments may take advantage of multi-material compliant mechanism in a ratchet-like configuration to achieve a novel ratchet-like mechanism. According to various embodiments, the multi-material ratchet-like mechanism may be prototyped using multi-material additive manufacturing technology.

[00013] According to various embodiments, instead of having a gear and pawl system, the multi-material ratchet- like mechanism may include two interfacing components or bodies with teeth. The two interfacing components or bodies may be identical. Each tooth may include both flexible/compliant material portion and rigid/stiff material portion. Accordingly, each tooth may include two portions. The flexible/compliant material portion may be placed behind a ratchet-like tooth tip portion (or the rigid/stiff material portion) that may be made from a stiffer material. In other words, the flexible/compliant material portion may be at the root or base portion of the tooth, while the ratchet-like tooth tip portion may be at the free-end of the tooth. The flexible/compliant material portion may form a compliant mechanism. The flexible/compliant material portion may play the role of the spring in classical ratchet mechanism for transferring the displacement of the ratchet-like tooth tip portion into localized elastic deformation in the flexible/compliant region. Accordingly, in this configuration, the tooth may accommodate large displacement of the ratchet-like tooth tip portion due to deformation of the flexible/compliant material in the direction of insertion of the interlocking component. The flexible/compliant material portion may also be responsible for returning the tooth to the original position/orientation/disposition after the tooth on a first component has move over a tooth on a second component. Therefore, the flexible/compliant material portion is also elastic. At the same time, the tooth may prohibit or impede or prevent movement of the interfacing components or bodies of the multi-material ratchet-like mechanism in the opposite direction due to the geometry of the ratchet-like tooth tip portion. Accordingly, asymmetrical configuration of the ratchet-like tooth tip portion with vertical surface on one side and an inclined surface on the other side may allow relative motion of the first component and the second component in the first direction and locking performance in the opposite second direction.

[00014] According to various embodiments, the compliant mechanism of the respective tooth may transfer or transform motion, force, or energy by gaining at least some of their mobility from the deflection of elastic material or through elastic body deformation rather than from movable mechanical joints. The compliant mechanism may be a monolithic (single-piece) or joint-less structure. According to various embodiments, each tooth of the respective interlocking component may be analogous to a multi-material compliant mechanism including a mixture of rigid part with integrated flexible material in selected segments such that the force or displacement of the mechanism may be controlled. Accordingly, the respective tooth of the interfacing components or bodies of the multi-material ratchet-like mechanism may adopt the advantages of multi-material compliant mechanism, in comparisons to traditional multi-links jointed mechanism, which include reduction of number of parts and elimination of assembly process, elimination of the need for lubrication, relief of stress from contact-induced loads, and storage of potential energy within the structure.

[00015] According to various embodiments, the multi-material ratchet-like mechanism may be a two-gear- system including identical compliant teeth. Accordingly, the compliant mechanism of the teeth may allow the two-gear-system to slide against each other in one direction and the geometry of the teeth may cause the two-gear- system to be locked in the opposite direction.

[00016] According to various embodiments, the multi-material ratchet-like mechanism may be tailored for different applications by changing different material and geometrical parameters. According to various embodiments, parameters such as elastic modulus of flexible region, thickness of flexible region, slope of wedges on the insertion, locking performance of the mechanism etc, may be varied depending on the applications. According to various embodiments, each of the interfacing components or bodies of the multi-material ratchet-like mechanism may also include one, or two, or more (or a plurality of) tooth.

[00017] According to various embodiments, the multi-material ratchet-like mechanism may be used in different applications such as interlocking joints for fastening three-dimensional (3D) printed parts together or as a captive fastener for assembly of furniture parts or attaching panels in automotive and building industries. The capacity of embedding the proposed multi-material ratchet-like mechanism as a region of other components and fabricating the entire part with multi-material additive manufacturing technology may be significant and different from other conventional fastening mechanism such as zip-tie. Furthermore, the strategic use of multi-material mechanism and the flexible base in the multi-material ratchet-like mechanism could be used to prevent vibration when using in high speed situations or as a system to cause energy absorption. Finally, multi-material printing approach may provide the ability to tailor the desired load-displacement behaviour of the multi-material ratchet-like mechanism due to the high control over the material layout and geometry.

[00018] According to various embodiments, when the multi-material ratchet-like mechanism is applied to an interlocking joint, the multi-material ratchet- like mechanism may allow easy insertion of one or two or more interlocking components while preventing them from dislodging by controlling the material layout and geometry at the contact surface. Accordingly, the interlocking joint may seek to control contact surface friction with the multi-material ratchet-like mechanism through integrating the principles of ratchet and compliant mechanisms. Further, the interlocking joint may function or behave according to that of the multi-material ratchet-like mechanism according to the various embodiments.

[00019] Accordingly, the interlocking joint may have been provided with interlocking contact surface that allows easy insertion while capable of resisting pull- out force. In the interlocking joint, the tangential traction behaviour of the contact surface may be controlled instead of controlling the normal force acting on the contact surface, whereby the tangential traction during insertion may be configured to be smaller than the tangential traction in the opposite direction (i.e. pull-out direction). Accordingly, a small tangential force may be required to insert the interlocking components for forming the interlocking joint while a larger tangential force may be required to pull apart the interlocking joint. According to various embodiments of the interlocking joint, the tangential traction of the contact surface may be view as being similar to the concept of friction, because the tangential traction may be considered as the force resisting the relative movement of the interlocking joint components in the direction of the respective relative movement. This is in contrast to the normal force acting on the contact surface which is how dislodgement is prevented in the conventional interlocking joint. Hence, the tangential traction behaviour at the contact surface of the interlocking joint may be important to the structural performance of the interlocking joint.

[00020] FIG. 1 shows an interlocking element 150, 170 of a multi-material ratchet- like mechanism 100 (see FIG. 2A to FIG. 2D) according to various embodiments. FIG. 2A to FIG. 2D illustrate how the multi-material ratchet-like mechanism 100 according to various embodiments may function. As shown, the multi-material ratchet-like mechanism 100 may include a first body 110 (for example a first component or a first interfacing component) mechanically or physically interfacing or interacting with a second body 130 (for example a second component or a second interfacing component) such that the first body 110 and the second body 130 may be movable relative to each other in a first direction 102 and may be prevented or prohibited or impeded or obstructed or restricted from relative movement in a second direction 104. Accordingly, the multi-material ratchet- like mechanism 100 may allow relative movement of the first body 110 and the second body 130 in one direction while the relative movement may be limited in an opposite direction. According to various embodiments, when the multi-material ratchet-like mechanism is applied in an interlocking joint, the first direction 102 may be an insertion direction for fitting or assembling or joining or connecting or uniting the first body 110 and the second body 130 with each other. Accordingly, the first direction 102 may be parallel to an axis of insertion. According to various embodiments, the second direction 104 may be a pulling-out direction for detaching or dislodging or disassembling or disconnecting or separating the first body 110 and the second body 130 from each other. Accordingly, the second direction 104 may be parallel to an axis of pulling-out. According to various embodiments, the first direction 102 and the second direction 104 may be opposite directions.

[00021] As shown, the multi-material ratchet-like mechanism 100 may further include a first interlocking element 150 (or a tooth or a first tooth) which may extend from a portion 112 of the first body 110. Further, the first interlocking element 150 may include a first compliant mechanism 152 between the portion 112 of the first body 110 and a tip portion 154 of the first interlocking element 150. Accordingly, the first interlocking element 150 may be a first protrusion projecting away from the portion 112 of the first body 110. According to various embodiments, the first protrusion may be a single continuous unit structure which may be integrally formed, molded or printed. According to various embodiments, the first protrusion may be projecting at least substantially perpendicularly away from the first body 110. According to various other embodiments, the first protrusion may be projecting at an angle (or an incline angle or a leaning angle) away from the first body 110. Hence, the first compliant mechanism 152 may be at the root portion of the first protrusion forming the first interlocking element 150. Thus, the first compliant mechanism 152 may be toward a proximal end of the first interlocking element 150 relative to the portion 112 of the first body 110. Further, the tip portion 154 may be the free-end portion or the extremity portion of the first protrusion forming the first interlocking element 150. Thus, the tip portion 154 may be toward a distal end of the first interlocking element 150 relative to the portion 112 of the first body 110. Accordingly, the first interlocking element 150 may be continuous or uninterrupted across the first interlocking element 150 from the first compliant mechanism 152 to the tip portion 154. Hence, a transition between the first compliant mechanism 152 and the tip portion 154 may be continuous and may be free of any physical or mechanical joints or fasteners. According to various embodiments, the first interlocking element 150 may be made of at least two different materials. Accordingly, the first compliant mechanism 152 may be made of a first material and the tip portion 154 of the first interlocking element 150 may be made of a second material, wherein the first material is different from the second material.

[00022] As also shown, the multi-material ratchet- like mechanism 100 may further include a second interlocking element 170 (or a corresponding tooth or a second tooth) which may extend from a corresponding portion 132 of the second body 130. Further, the second interlocking element 170 may include a second compliant mechanism 172 between the corresponding portion 132 of the second body 130 and a corresponding tip portion 174 of the second interlocking element 170. Accordingly, the second interlocking element 170 may be a second protrusion projecting away from the corresponding portion 132 of the second body 130. According to various embodiments, the second protrusion may be a single continuous unit structure, which may be integrally formed, molded or printed. According to various embodiments, the second protrusion may be projecting at least substantially perpendicularly away from the second body 130. According to various other embodiments, the second protrusion may be projecting at an angle (or an incline angle or a leaning angle) away from the second body 130. Hence, the second compliant mechanism 172 may be at the root portion of the second protrusion forming the second interlocking element 170. Thus, the second compliant mechanism 172 may be toward a proximal end of the second interlocking element 170 relative to the corresponding portion 132 of the second body 130. Further, the corresponding tip portion 174 may be the free-end portion or the extremity portion of the second protrusion forming the second interlocking element 170. Thus, the corresponding tip portion 174 may be toward a distal end of the second interlocking element 170 relative to the corresponding portion 132 of the second body 130. Accordingly, the second interlocking element 170 may be continuous or uninterrupted across the second interlocking element 170 from the second compliant mechanism 172 to the tip portion 174. Hence, a transition between the second compliant mechanism 172 and the corresponding tip portion 174 may be continuous and may be free of any physical or mechanical joints or fasteners. According to various embodiments, the second interlocking element 170 may be made of at least two different materials. Accordingly, the second compliant mechanism 172 may be made of a first material and the corresponding tip portion 174 of the second interlocking element 170 may be made of a second material, wherein the first material is different from the second material.

[00023] According to various embodiments, the first interlocking element 150 of the first body may be identical to the second interlocking element 170 of the second body 130. Accordingly, the multi-material ratchet-like mechanism 100 may be formed by interfacing the side of the first body 110 having the first interlocking element 150 with the corresponding side of the second body 130 having the identical second interlocking element 170, and orientating the first body 110 and the second body 130 such that the first interlocking element 150 and the second interlocking element 170 are facing opposite directions or disposed in opposite orientation.

[00024] According to various embodiments, the respective first compliant mechanism 152 and the second compliant mechanism 172 may include a single-piece flexible member (or structure) configured to transmit or transfer or transform or convert an applied force or an applied energy into a relative motion or a relative displacement between two ends of the single-piece flexible member through elastic deformation or deflection of the single -piece flexible member. According to various embodiments, the materials of the respective first compliant mechanism 152 and the second compliant mechanism 172 may include elastic and/or flexible and/or deformable materials having the ability to deform under an application of an external force or energy and to return to the original state upon removal of the application of the external force or energy. Accordingly, the materials of the respective first compliant mechanism 152 and the second compliant mechanism 172 may have lower elastic modulus. According to various embodiments, any elastomers having low Young's modulus and high failure strain may be suitable material for the respective first compliant mechanism 152 and the second compliant mechanism 172. For example, the material may include rubber-like 3D printing materials such as "TangoPlus FLX 930 (Shore 27A)" and "Agilus30 FLX935 (Shore 30A)" from the Stratasys company.

[00025] According to various embodiments, the tip portion 154 of the first interlocking element 150 may be of a higher stiffness than the first compliant mechanism 152 such that the tip portion 154 may be more rigid than the first compliant mechanism 152. In other words, the first compliant mechanism 152 may be more flexible or more pliable as compared to the tip portion 154 of the first interlocking element 150. Accordingly, the tip portion 154 may not deform under an application of a force or an energy on the tip portion 154, and may transmit or transfer the applied force or applied energy to the first compliant mechanism 152 for causing a deflection or elastic deformation of the first compliant mechanism 152 to result in a relative displacement or relative motion between the tip portion 154 of the first interlocking element 150 and the first body 110. According to various embodiments, the tip portion 154 of the first interlocking element 150 may be made of a different material from that of the first compliant mechanism 152. The material of the tip portion 154 of the first interlocking element 150 may have a higher elastic modulus than the material of the first compliant mechanism 152. According to various embodiments, the tip portion 154 of the first interlocking element 150 may also be configured or shaped or dimensioned or profiled so as to achieve a higher rigidity. According to various embodiments, the material of the tip portion 154 may include any polymer having high Young's modulus and high failure resistance. For example, the materials may include 3D printing materials named Vero from Stratasys company.

[00026] According to various embodiments, the corresponding tip portion 174 of the second interlocking element 170 may also be of a higher stiffness than the second compliant mechanism 172 such that the corresponding tip portion 174 may be more rigid than the second compliant mechanism 172. In other words, the second compliant mechanism 172 may be more flexible or more pliable as compared to the corresponding tip portion 174 of the second interlocking element 170. Accordingly, the corresponding tip portion 174 may not deform under an application of a force or an energy on the corresponding tip portion 174, and may transmit or transfer the applied force or applied energy to the second compliant mechanism 172 for causing a deflection or elastic deformation of the second compliant mechanism 172 to result in a relative displacement or relative motion between the corresponding tip portion 174 of the second interlocking element 170 and the second body 130. According to various embodiments, the corresponding tip portion 174 of the second interlocking element 170 may be made of a different material from that of the second compliant mechanism 172. The material of the corresponding tip portion 174 of the second interlocking element 170 may have a higher elastic modulus than the material of the second compliant mechanism 172. According to various embodiments, the corresponding tip portion 174 of the second interlocking element 170 may also be configured or shaped or dimensioned or profiled so as to achieve a higher rigidity. According to various embodiments, the material of the corresponding tip portion 174 may include any polymer having high Young's modulus and high failure resistance. For example, the materials may include 3D printing materials named Vero from Stratasys company.

[00027] According to various embodiments, the tip portion 154 of the first interlocking element 150 and the first body 110 may be made of the same material. Similarly, the corresponding tip portion 174 of the second interlocking element 170 and the second body 130 may be made of the same material. According to various embodiments, the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 may be made of the same material. According to various embodiments, the first body 110 and the second body 130 may be made of the same material. According to various embodiments, the first compliant mechanism 152 and the second compliant mechanism 172 may be made of the same material.

[00028] FIG. 2A shows the relative positions of the first interlocking element 150 and the second interlocking element 170 in a 'pre-interlock' disposition according to various embodiments. FIG. 2B shows the interactions and behaviors of the first interlocking element 150 and the second interlocking element 170 when the first interlocking element 150 and the second interlocking element 170 are engaged toward each other in the first direction 102 from the 'pre-interlock' disposition according to various embodiments. FIG. 2C shows the relative positions of the first interlocking element 150 and the second interlocking element 170 in an 'interlocked' disposition according to various embodiments. FIG. 2D shows the interactions and behaviors of the first interlocking element 150 and the second interlocking element 170 when the first interlocking element 150 and the second interlocking element 170 are engaged toward each other in the second direction 104 from the 'interlocked' disposition according to various embodiments.

[00029] As shown in FIG. 2A and FIG. 2B, the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 may be configured to cause elastic deformation of the respective first compliant mechanism 152 and second compliant mechanism 172 so as to slide over each other when engaging in the first direction 102 such that the first body 110 and the second body 130 may be movable relative to each other. Further, as shown in FIG. 2C and FIG. 2D, the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 may be further configured to lock against each other when engaging in the second direction 104 such that the first body 110 and the second body 130 may be interlocked or prevented from relative movement.

[00030] As shown in FIG. 2D, when the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 are engaged in the second direction 104 from the 'interlocked' disposition, a limited relative movement in the second direction 104 due to the elastic deformation of the respective first compliant mechanism 152 and the second compliant mechanism 172 may be allowed in the available gaps until the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 are physically stopped or blocked or obstructed. As shown, even when the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 are physically stopped or blocked or obstructed in the second direction 104, the first body 110 and the second body 130 may remain interlock. Accordingly, in order to relatively move the first body 110 and the second body 130 in the second direction 104, the first interlocking element 150 and the second interlocking element 170 may have to be subjected to a force or an energy that is sufficiently large to cause a failure of the first interlocking element 150 and/or the second interlocking element 170. For example, when a force greater than fracture strength is applied, a material failure of the first compliant mechanism 152 and/or the second compliant mechanism 172 and/or the tip portion 154 of the first interlocking element 150 and/or the corresponding tip 174 of the second interlocking element 170 may result in fractures. Accordingly, the first body 110 and the second body 130 may then be moved relatively with respect to each other in the second direction 104.

[00031] In comparison, as shown in FIG. 2B, relatively movement of the first body 110 and the second body 130 in the first direction may only require a force that is sufficient to deform the respective first compliant mechanism 152 and second compliant mechanism 172 as well as to overcome fnctional force due to the contact between the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170.

[00032] Therefore, the multi-material ratchet-like mechanism 100 according to various embodiments may allow easy relative movement between the first body 110 and the second body 130 with respect to each other in the first direction 102 from the 'pre-interlock' state into the 'interlocked' state. Further, in the 'interlocked' state, the multi-material ratchet- like mechanism 100 may prevent relative movement of the first body 110 and the second body 130 with respect to each other in the second direction 104 unless the multi-material ratchet-like mechanism 100 is subjected to a force or an energy in the second direction 104 which may be significantly large enough to fracture the first interlocking element 150 and/or the second interlocking element.

[00033] Referring back to FIG. 2C and FIG. 2D, the tip portion 154 of the first interlocking element 150 may include a stop surface 156. As shown in FIG. 2C, the stop surface 156 of the tip portion 154 of the first interlocking element 150 may be at least substantially perpendicular to the second direction 104 when the first compliant mechanism 152 of the first interlocking element 150 is in an undeformed state. According to various embodiments, the stop surface 156 of the tip portion 154 of the first interlocking element 150 may also be at an angle (or a leaning angle) or inclined relative to the second direction 104 when the first compliant mechanism 152 of the first interlocking element 150 is in an undeformed state. Referring back to FIG. 2A and FIG. 2B, the first interlocking element 150 may include a slide surface 158. The slide surface 158 may be angled relative to the stop surface 156. Further, the slide surface 158 may be configured for sliding engagement with the corresponding tip portion 174 of the second interlocking element 170. As shown in FIG. 2A to FIG. 2D, the stop surface 156 and the slide surface 158 may be configured such that the tip portion 154 of the first interlocking element 150 may resemble a wedge shape. Accordingly, the slide surface 158 may be an inclined surface of the wedge shape and the stop surface 156 may be a vertical surface of the wedge shape.

[00034] Similarly, the corresponding tip portion 174 of the second interlocking element 170 may also include a corresponding stop surface 176. As shown in FIG. 2C, the corresponding stop surface 176 of the tip portion 174 of the second interlocking element 170 may be at least substantially perpendicular to the second direction 104 when the second compliant mechanism 172 of the second interlocking element 170 is in an undeformed state. According to various embodiments, the corresponding stop surface 176 of the tip portion 174 of the second interlocking element 170 may be at an angle (or a leaning angle) or inclined relative to the second direction 104 when the second compliant mechanism 172 of the second interlocking element 170 is in an undeformed state. Referring back to FIG. 2A and FIG. 2B, the second interlocking element 170 may include a corresponding slide surface 178. The corresponding slide surface 178 may be angled relative to the corresponding stop surface 176. Further, the corresponding slide surface 178 of the second interlocking element may be configured for sliding engagement with the slide surface 158 of the first interlocking element 150. As shown in FIG. 2A to FIG. 2D, the corresponding stop surface 176 and the corresponding slide surface 178 may be configured such that the corresponding tip portion 174 of the second interlocking element 170 may resemble a wedge shape. Accordingly, the corresponding slide surface 178 may be an inclined surface of the wedge shape and the corresponding stop surface 176 may be a vertical surface of the wedge shape.

[00035] According to various embodiments, the slide surface 158 of the tip portion 154 of the first interlocking element 150 may be angled less than 90° with respect to the stop surface 156 of the tip portion 154 of the first interlocking element 150. According to various embodiments, the angle between the slide surface 158 of the tip portion 154 of the first interlocking element 150 and the stop surface 156 of the tip portion 154 of the first interlocking element 150 may be less than 90°. Further, depending on the required or desired mechanical behaviour, the angle between the slide surface 158 of the tip portion 154 of the first interlocking element 150 and the stop surface 156 of the tip portion 154 of the first interlocking element 150 may be varied by ranging the angle such as from 65° to 89°, or from 75° to 89°, or from 65° to 85°, or from 75° to 85°, because the first interlocking element 150 may behaviour differently depending on the angle.

[00036] According to various embodiments, the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 may also be angled less than 90° with respect to the corresponding stop surface 176 of the tip portion 174 of the second interlocking element 170. According to various embodiments, the angle between the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 and the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may be less than 90°. Further, depending on the required or desired mechanical behaviour, the angle between the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 and the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may be varied by ranging the angle such as from 65° to 89°, or from 75° to 89°, or from 65° to 85°, or from 75° to 85°, because the second interlocking element 170 may behaviour differently depending on the angle.

[00037] According to various embodiments, the angle between the slide surface 158 of the tip portion 154 of the first interlocking element 150 and the stop surface 156 of the tip portion 154 of the first interlocking element 150 and the angle between the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 and corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may be the same.

[00038] FIG. 2A shows the start of the insertion (relative movement in the first direction 102) of the multi-material ratchet- like mechanism 100 whereby two ratchet- like components (or bodies 110, 130) with respective tooth (i.e. the first interlocking element 150 and the second interlocking element 170) are ready to work. As shown in FIG. 2A, in the 'pre-interlock' disposition, an engagement surface 114 of the first body 110 may be placed flat against a corresponding engagement surface 134 of the second body 130 with the first interlocking element 150 and the second interlocking element 170 spaced laterally apart from each other in a first order (e.g. the first interlocking element 150 on the left and the second interlocking element 170 on the right as shown in FIG. 2A). The first interlocking element 150 may be at least substantially perpendicular to the engagement surface 114 of the first body 110 and the second interlocking element 170 may be at least substantially perpendicular to the corresponding engagement surface 134 of the second body 130. Further, the first interlocking element 150 may be configured such that the stop surface 156 of the tip portion 154 of the first interlocking element 150 may be facing away from the second interlocking element 170 (e.g. the stop surface 156 facing to the left when the second interlocking element 170 is on the right as shown in FIG. 2A). Similarly, the second interlocking element 170 may be configured such that the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may be facing away from the first interlocking element 150 (e.g. the corresponding stop surface 176 facing to the right when the first interlocking element 150 is on the left as shown in FIG. 2A). Accordingly, the slide surface 158 of the tip portion 154 of the first interlocking element 150 may be inclined with the lower edge directed toward the second interlocking element 170, and the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 may be inclined with the corresponding lower edge directed toward the first interlocking element 150. According to various embodiments, the slide surface 158 of the tip portion 154 of the first interlocking element 150 may be at least substantially parallel to the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170.

[00039] FIG. 2B shows the insertion when the teeth (i.e. the first interlocking element 150 and the second interlocking element 170) are in contact with each other and the respective first and second compliant mechanisms 152, 172 behind respective tip portions 154, 174 tolerates deformation required to complete the insertion step. As shown in FIG. 2B, as the first body 110 and the second body 130 are moved relatively in the first direction 102 such that the first interlocking element 150 and the second interlocking element are moved relatively toward each other, the slide surface 158 of the tip portion 154 of the first interlocking element 150 may contact the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 and bear flat against each other. As relative movement between the first body 110 and the second body 130 continues, the forces acting on the slide surface of the first interlocking element 150 and the corresponding slide surface 178 of the second interlocking element 170 may be transmitted or transferred to the respective first compliant mechanism 152 and second compliant mechanism 154 to cause elastic deformation of the respective first compliant mechanism 152 and the second compliant mechanism 154. As a result of the elastic deformation of the respective first compliant mechanism 152 and the second compliant mechanism 154, the orientation and/or the disposition of the tip portion 154 of the first interlocking element 150 and the corresponding tip portion 174 of the second interlocking element 170 may be changed or altered such that the slide surface 158 of the tip portion 154 of the first interlocking element 150 and the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 may be oriented at least substantially parallel to the first direction so as to slide over each other.

[00040] FIG. 2C shows the multi-material ratchet-like mechanism 100 after the insertion. As shown, the respective first and second compliant mechanism 152, 172 may return back to their initial configuration (i.e. undeformed state). Accordingly the respective teeth (i.e. the first interlocking element 150 and the second interlocking element 170) may then stand up back to back which may limit relative movement of the first body 110 and the second body 130 in the opposite second direction 104 (i.e. pull-out direction). As shown in FIG. 2C, after the relative movement of the first body 110 and the second body 130 in the first direction 102 has caused the slide surface 158 of the tip portion 154 of the first interlocking element 150 and the corresponding slide surface 178 of the corresponding tip portion 174 of the second interlocking element 170 to slide over each other, the respective first and second compliant mechanism 152, 172 may return to the respective undeformed state. Accordingly, the first body 110 and the second body 130 may be in the 'interlocked' disposition. In the 'interlocked' disposition, the order of the first interlocking element 150 and the second interlocking element 170 may be reversed (e.g. the first interlocking element 150 may be on the right and the second interlocking element 170 may be on the left as shown in FIG. 2C). Accordingly, the stop surface 156 of the tip portion 154 of the first interlocking element 150 and the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may be facing toward each other (e.g. the stop surface 156 facing to the left and the corresponding stop surface 176 facing to the right when the first interlocking element 150 is on the right and the second interlocking element 170 is on the left as shown in FIG. 2C) or interfacing each other such that the stop surface 156 of the first interlocking element 150 and the corresponding stop surface 176 of the second interlocking element 170 may engage and contact each other in the second direction. Hence, the stop surface 156 of the tip portion 154 of the first interlocking element 150 and the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may bear flat against each other so as to lock against each other for preventing relative movement of the first body 110 and the second body 130 in the second direction.

[00041] FIG. 2D shows how the multi-material ratchet-like mechanism 100 may work against a pull-out force (or relative movement in the second direction 104). As shown, the multi-material ratchet-like mechanism 100 may allow limited relative movement between the first body 110 and the second body 130 in the second direction 104 from the 'interlocked' disposition. However, the multi-material ratchet-like mechanism 100 may be configured to form a lasting interlock between the first body 110 and the second body 130 in the second direction 104 unless the pull-out force is large enough (or the relative movement in the second direction 104 is of sufficient force) to fracture the first interlocking element 150 and/or the second interlocking element 170.

[00042] Referring back to FIG. 2A, the first body 110 may include a recess 116 and the first interlocking element 150 may extend from a base portion 118 of the recess 116. Further, the tip portion 154 of the first interlocking element 150 may protrude out of the recess 116 of the first body 110. According to various embodiments, there may be a gap 190 between the sides of the first interlocking element 150 and the inner walls 120 of the recess 116 of the first body 110. The gap 190 may be configured to provide a space or room for the tip portion 154 of the first interlocking element 150 to change or alter its orientation or disposition as the first compliant mechanism 152 deforms elastically. As also shown, an inner wall portion 122 of the recess 116 immediately adjacent to the stop surface 156 of the tip portion 154 of the first interlocking element 150 may include a chamfered edge 124 at a rim portion 126 of the recess 116. Referring to FIG. 2C, the chamfered edge 124 may be configured to provide a space or room to accommodate the tip portion 154 of the first interlocking element 150 such that the first compliant mechanism 152 may return fully to the undeformed state (i.e. free of being subject to any forces) when in the 'interlocked' disposition.

[00043] Referring back to FIG. 2A, the second body 130 may similarly include a corresponding recess 136 and the second interlocking element 170 may extend from a base portion 138 of the recess 136. Further, the corresponding tip portion 174 of the second interlocking element 170 may protrude out of the recess 136 of the second body 130. According to various embodiments, there may be a corresponding gap 192 between the sides of the second interlocking element 170 and the corresponding inner walls 140 of the corresponding recess 136 of the second body 130. The corresponding gap 192 may be configured to provide a corresponding space or room for the corresponding tip portion 174 of the second interlocking element 170 to change or alter its orientation or disposition as the second compliant mechanism 172 deforms elastically. As also shown, a corresponding inner wall portion 142 of the corresponding recess 136 immediately adjacent to the corresponding stop surface 176 of the corresponding tip portion 174 of the second interlocking element 170 may include a corresponding chamfered edge 144 at a corresponding rim portion 146 of the corresponding recess 136. Referring to FIG. 2C, the corresponding chamfered edge 144 may be configured to provide a space or room to accommodate the corresponding tip portion 174 of the second interlocking element 170 such that the second compliant mechanism 172 may return fully to the undeformed state (i.e. free of being subject to any forces) when in the 'interlocked' disposition.

[00044] According to various embodiments, the first compliant mechanism 152 may have a height of 5mm or less when the first interlocking element 150 is approximately 10mm in height. Similarly, the second compliant mechanism 172 may have a height of 5mm or less when the second interlocking element 170 is approximately 10mm in height. According to various embodiments, the first compliant mechanism 152 and the second compliant mechanism 172 may have the same height.

[00045] According to various embodiments, at least one of the slide surface 158 of the first interlocking element 150 or the corresponding slide surface 178 of the second interlocking element 170 may be treated or machined or surface finished to reduce friction so as to minimize the force required to slide the tip portion 154 of the first interlocking element 150 over the corresponding tip portion 174 of the second interlocking element 170 during insertion. According to various embodiments, at least one of the stop surface 156 of the first interlocking element 150 or the corresponding stop surface 176 of the second interlocking element 170 may be treated or machined or surface finished to increase friction so as to enhance the effect of locking the tip portion 154 of the first interlocking element 150 against the corresponding tip portion 174 of the second interlocking element 170 in the 'interlock' disposition.

[00046] FIG. 3 shows a body 310 having an interlocking element 350 according to various embodiments. Two of the bodies 310 may be provided to form a multi- material ratchet-like mechanism according to the various embodiments. Accordingly, the two bodies 310 may be configured similarly to the first body 110 and the second body 130 of the multi-material ratchet-like mechanism 100 of FIG. 2A to FIG. 2D. However, the body 310 of FIG. 3 may differ from the first body 110 and the second body 130 of the multi-material ratchet-like mechanism 100 of FIG. 2A to FIG. 2D in that a further inner wall portion 328 of the recess 316 immediately adjacent to an opposite side 360 of the stop surface 356 of the interlocking element 350 may include a step 329 at a base edge 327 of the further inner wall portion 328. Further, as shown in FIG. 3, a corner 362 between the slide surface 358 and the stop surface 356 of the tip portion 354 of the interlocking element 350 may be rounded.

[00047] FIG. 4A shows an unassembled view of an interlocking joint 400 having the multi-material ratchet-like mechanism according to various embodiments. FIG. 4B shows an assembled view of the interlocking joint 400 of FIG. 4A according to various embodiments. As shown, the interlocking joint 400 may include a first body 410 and a second body 430 configured to form the multi-material ratchet-like mechanism according to various embodiments. The first body 410 may include a transverse portion 411 and a leg portion 413 extending perpendicularly from the transverse portion 411 such that the first body 410 may have a T-shape cross-section. Further, the first body 410 may include one or more interlocking elements 450 on two opposite surfaces 415, 417 of the leg portion 413 of the first body 410. According to various embodiments, the first body 410 may include one or more interlocking elements 450 on one or more surfaces of the leg portion 413 of the first body 410. The second body 430 may include a base portion 431 and two wall portions 433, 435, one extending perpendicularly from one end of the base portion 431 and the other extending perpendicularly from the other end of the base portion 431. Accordingly, the second body 430 may have a U-shape cross-section. Further, the second body 430 may include one or more interlocking elements 470 on two opposing inner wall surfaces 437, 439 of the respective wall portions 433, 435.

[00048] As shown in FIG. 4B, the leg portion 413 of the first body 410 may be inserted between the two wall portions 433, 435 of the second body 430 such that the interlocking elements 450 may interface or interact with the interlocking elements 470 according to the various embodiments as described herein to allow easy relative movement between the first body 410 and the second body 430 for assembling of the first body 410 and the second body 430, and to interlock firmly after the first body 410 and the second body 430 have been assembled. [00049] According to various embodiments, the multi-material ratchet-like mechanism may be manufactured by multi-material fabrication techniques or multi- material additive manufacturing technologies. For example, multi-material three- dimensional printing technology may be used. Accordingly, the multi-material compliant ratchet-like mechanism or the interlocking joint may be fabricated using multi-material three-dimensional printing technology. According to various embodiments, multi-material additive manufacturing (MMAM) technologies may provide the capability of mixing and depositing multiple materials in a single print job built progressively in layers. According to an implementation of an embodiment, the OBJET Connex 3D printer - a machine that employs PolyJet Matrix Technology which dispenses materials from designated micro-scale inkjet printing nozzles, may be used. Accordingly, in the embodiment, the materials used in the fabrication, excluding the support material, may be the Vero and Tango-series materials, where Vero-series materials are thermoset polymers with elastic modulus of 2020 MPa, and Tango-series materials are elastomers with elastic modulus of around 0.6 MPa. As shown in FIG. 2A, the tip portion 154 of the first interlocking element 150 may be made of the Vero- series materials, while the first compliant mechanism 152 may be made of Tango- series materials. Further, the first body 110 may also be made of Vero-series materials. Similarly, the corresponding tip portion 174 of the second interlocking element 170 may be made of the Vero-series materials and the second compliant mechanism 152 may be made of Tango- series materials. The second body 110 may also be made of Vero-series materials.

[00050] According to various embodiments, there is provided a multi-material ratchet-like mechanism including a first body and a second body interfacing the first body. The multi-material ratchet-like mechanism may further include a first interlocking element which extends from a portion of the first body and which includes a first compliant mechanism between the portion of the first body and a tip portion of the first interlocking element. The multi-material ratchet-like mechanism may further include a second interlocking element which extends from a corresponding portion of the second body and which includes a corresponding tip portion. According to various embodiments, the tip portion of the first interlocking element may be configured to cause elastic deformation of the first compliant mechanism so as to slide the tip portion of the first interlocking element over the corresponding tip portion of the second interlocking element when engaging each other in the first direction. According to various embodiments, the tip portion of the first interlocking element may be further configured to lock against the corresponding tip portion of the second interlocking element when engaging each other in the second direction. According to various embodiments, the first interlocking element may be a continuous structure. Accordingly, the first interlocking element may be a single uninterrupted protrusion whereby the first compliant mechanism may be a portion or a part of the uninterrupted protrusion. According to various embodiments, the first compliant mechanism and the tip portion of the first interlocking element may be made of different materials.

[00051] According to various embodiments, the second interlocking element may include a second compliant mechanism between the corresponding portion of the second body and the corresponding tip portion of the second interlocking element. According to various embodiments, the second interlocking element may be a continuous structure. Accordingly, the second interlocking element may be a single uninterrupted protrusion whereby the second compliant mechanism may be a portion or a part of the uninterrupted protrusion. According to various embodiments, the second compliant mechanism and the tip portion of the second interlocking element may be made of different materials.

[00052] According to various embodiments, the corresponding tip portion of the second interlocking element may be configured to cause elastic deformation of the second compliant mechanism when engaging the tip portion of the first interlocking element in the first direction. According to various embodiments, the corresponding tip portion of the second interlocking element may be further configured to lock against the tip portion of the first interlocking element when engaging in the second direction.

[00053] Accordingly, multi-material ratchet-like mechanism may be configured such that the first body and the second body are movable relative to each other in the first direction and are prevented from relative movement in the second direction. According to various embodiments, the first direction may be opposite the second direction.

[00054] According to various embodiments, the tip portion of the first interlocking element may be of a higher stiffness than the first compliant mechanism. Further, the corresponding tip portion of the second interlocking element may be of a higher stiffness than the second compliant mechanism. [00055] According to various embodiments, the tip portion of the first interlocking element may include a stop surface and a slide surface angled relative to the stop surface. The stop surface of the tip portion of the first interlocking element may be at least substantially perpendicular to the second direction when the first compliant mechanism of the first interlocking element is in an undeformed state. According to various other embodiments, the stop surface of the tip portion of the first interlocking element may be inclined relative to the second direction when the first compliant mechanism of the first interlocking element is in an undeformed state. According to various embodiments, the slide surface of the tip portion of the first interlocking element may be angled less than 90 degrees with respect to the stop surface of the tip portion of the first interlocking element.

[00056] According to various embodiments, the corresponding tip portion of the second interlocking element may include a corresponding stop surface and a corresponding slide surface angled relative to the corresponding stop surface. The corresponding stop surface of the corresponding tip portion of the second interlocking element may be at least substantially perpendicular to the second direction when the second compliant mechanism of the second interlocking element is in an undeformed state. According to various other embodiments, the corresponding stop surface of the corresponding tip portion of the second interlocking element may be inclined relative to the second direction when the second compliant mechanism of the second interlocking element is in an undeformed state. According to various embodiments, the corresponding slide surface of the corresponding tip portion of the second interlocking element may be angled less than 90 degrees with respect to the corresponding stop surface of the corresponding tip portion of the second interlocking element.

[00057] According to various embodiments, when engaging the first interlocking element and the second interlocking element in the first direction, the slide surface of the tip portion of the first interlocking element and the corresponding slide surface of the corresponding tip portion of the second interlocking element may be configured to bear flat against each other to cause the elastic deformation of the respective first and second compliant mechanisms such that the slide surface of the first interlocking element and the corresponding slide surface of the second interlocking element may be oriented at least substantially parallel to the first direction so as to slide over each other. [00058] According to various embodiments, when engaging the first interlocking element and the second interlocking element in the second direction, the stop surface of the tip portion of the first interlocking element and the corresponding stop surface of the corresponding tip portion of the second interlocking element may be configured to bear flat against each other so as to lock against each other to prevent relative movement in the second direction.

[00059] According to various embodiments, the first body may include a recess and the first interlocking element may extend from a base portion of the recess. Further, the tip portion of the first interlocking element may protrude out of the recess of the first body. According to various embodiments, an inner wall portion of the recess immediately adjacent to the stop surface of the first interlocking element may include a chamfered edge at a rim portion of the recess. According to various embodiments a further inner wall portion of the recess immediately adjacent to an opposite side of the stop surface of the first interlocking element may include a step at a base edge of the further inner wall portion.

[00060] According to various embodiments, the second body may include a corresponding recess and the second interlocking element may extend from a corresponding base portion of the corresponding recess. Further, the corresponding tip portion of the second interlocking element may protrude out of the corresponding recess of the second body. According to various embodiments, a corresponding inner wall portion of the corresponding recess immediately adjacent to the corresponding stop surface of the second interlocking element may include a corresponding chamfered edge at a corresponding rim portion of the corresponding recess. According to various embodiments, a corresponding further inner wall portion of the corresponding recess immediately adjacent to an opposite side of the corresponding stop surface of the second interlocking element may include a corresponding step at a corresponding base edge of the corresponding further inner wall portion.

[00061] According to various embodiments, the respective first and second compliant mechanism may include a height of 5mm or less.

[00062] According to various embodiments, at least one of the slide surface of the first interlocking element or the corresponding slide surface of the second interlocking element may be treated or machined or surface finished for reducing friction. According to various embodiments, at least one of the stop surface of the first interlocking element or the corresponding stop surface of the second interlocking element may be treated or machined or surface finished for increasing friction.

[00063] According to various embodiments, the first body may include a plurality of the first interlocking elements and the second body may include a plurality of the second interlocking elements.

[00064] Various embodiments have provided a multi-material ratchet-like mechanism that exhibits the advantages of traditional ratchet mechanisms as well as the multi-material compliant mechanisms. In the traditional ratchet mechanism, the ratchet mechanism allows the moving of gears or teeth in one direction while the motion is limited in the opposite direction. In the various embodiments, similar advantage may be achieved. However, instead of using "gear" and "pawl" in traditional ratchet mechanism, two teeth with the same geometry may be used in the various embodiments to allow the linear motion and interlocking. Further, various embodiments have also exhibited the advantage of the conventional multi-material compliant mechanism, which may include some stiff or rigid parts with soft or compliant materials, whereby various embodiments may achieve large elastic deformation without disruption of structure or function. Accordingly, various embodiments may have the ability to transfer motion, force and energy as well as store strain energy in the soft material part.

[00065] Various embodiments have provided a linear multi-material ratchet-like mechanism or interlocking joint that may behave as a ratchet-like mechanism with the multi-material compliant mechanism. According to various embodiments, the fabrication process may be easy and fast with the use of three-dimensional printing technology, and the multi-material ratchet-like mechanism may be capable of being assembled to create one direction locking mechanism between sliding parts.

[00066] Various experiments and computer simulations may be conducted to test the various embodiments. Some of the results of the experiments and computer simulations are provided in the following.

[00067] Various experiments may be conducted for testing both insertion and locking performance of the multi-material ratchet-like mechanism according to the various embodiments.

[00068] In the following, experimental and computational investigations of the force-displacement behaviour of a multi-material ratchet-like mechanism according to various embodiments are described. These investigations may include the operation and performance of the multi-material ratchet-like mechanism in both directions of insertion and locking. Since, one of the objectives of the multi-material ratchet-like mechanism is to have a ratchet-like mechanism that allows the movement of the parts in one direction while it resists the motion in opposite direction, measurements and evaluation of the applied force during the insertion and locking performance may be conducted.

[00069] For the computational investigation, a three-dimensional finite element model may be first constructed, for example, in ABAQUS software (ABAQUS, 2016) to analyze the mechanical behaviour of the multi-material ratchet-like mechanism in two opposite directions of motion. The analysis may determine the required applied forces for moving the parts against each other in the insertion direction and the maximum resistance force in the locking direction. Furthermore, measurements of the localized elastic deformation and stress distribution in flexible regions may be obtained that may be used in further modifications for specific applications.

[00070] For the experimental investigation, to explore the multi-material ratchet-like mechanism experimentally, a matching fixture made of aluminium with 'male' and 'female' jigs to fit the fabricated multi-material samples may be prepared as shown in FIG. 5(a). Measurements of the applied force for insertion may be obtained in a compression test and evaluation of the resistance force in the locking direction may be conducted in the tensile test. All the experimental measurements may be performed, for example, by an Instron 5943 machine with 1 KN load cell. FIG. 5(b) and FIG. 5(c) show the experimental setups during insertion and locked directions, respectively.

[00071] Accordingly, to investigate the mechanical behaviour of one embodiment of the multi-material ratchet-like mechanism, the required forces for movement in the two different directions may be determined computationally with the finite element (FE) method and compared with the experimental results of the physical tensile/compression tests.

[00072] FIG. 6 shows a summary of the analysis of the mechanical behaviour of one embodiment of the multi-material ratchet- like mechanism during the insertion process by finite element simulation and physical experiments. This includes the comparison of force-displacement behaviour predicted by finite element simulation with experimental measurements. Furthermore, the localized deformation distribution is also illustrated in specific key events during the insertion step. FIG. 6(a) shows the force-displacement graph of the experimental data. FIG. 6(b) - FIG. 6(e) show the corresponding steps with the physical experiment (left), and the maximum principal strain contour that is calculated by FE simulation (centre and right). The steps of FIG. 6(b) - FIG. 6(e) demonstrate key events during the insertion process in chronological order: FIG. 6(b) initial configuration; FIG. 6(c) first stage of insertion performance (only elastic deformation in flexible region); FIG. 6(d) second stage of insertion performance (elastic deformation in flexible region and rigid-rigid contact); and FIG. 6(e) completion of insertion.

[00073] As shown in FIG. 6(a), there is a good qualitative and quantitative agreement between the force-displacement behaviour calculated by finite element simulations and the data that is measured experimentally. Therefore, the finite element method may be successful in predicting the maximum reaction force which is necessary to complete the insertion step. Furthermore, the finite element and experimental results both capture the same physical phenomenon and deformation stages that are elaborated in the following.

[00074] The insertion process may start from the initially stress-free and un- deformed state as shown in FIG. 6(b). Then the reaction force gradually increases as the teeth begin to interface each other and the rigid body motion of the teeth transfers to local elastic deformation in the flexible region as can be seen in FIG. 6(c). Furthermore, the strain distribution contour plots in FIG. 6(b) to FIG. 6(e) illustrate the maximum elastic deformation in the flexible region that may be caused by movement of parts in different insertion stages.

[00075] Upon further motion, both teeth may begin to contact the walls of the base platform which are situated directly behind as depicted in FIG. 6(d). This scenario of stiff parts being forced against one another may create a resistance and lead to the observed peak where the reaction force increases to its maximum of 12 N. The completion of the insertion process is demonstrated in FIG. 6(e), where the two teeth pass each other to achieve a relaxed configuration after finishing the insertion motion. This may result in the reaction force decreasing to 0 N as all regions reverting to a stress-free scenario and the elastic deformation of the flexible region may be recovered.

[00076] FIG. 7 shows a summary of the analysis of the mechanical behaviour of one embodiment of the multi-material ratchet-like mechanism in the locking direction by finite element simulation and physical experiments. FIG. 7 features the force- displacement behaviour at the different key events during the motion in the locking direction. FIG. 7(a) shows the force-displacement graph of the experimental data. FIG. 7(b) - FIG. 7(e) show the corresponding steps with the physical experiment (left), and the maximum principal strain contour that is calculated by FE simulation (centre and right). The steps of FIG. 7(b) - FIG. 7(e) demonstrate key events during the locking process in chronological order: FIG. 7(b) initial configuration; FIG. 7(c) first stage of locking performance (only elastic deformation in flexible region); FIG. 7(d) second stage of locking performance (elastic deformation in flexible region and rigid-rigid contact); and FIG. 7(e) failure of flexible region.

[00077] FIG. 7(a) illustrates that the finite element results and experimental measurements of force-displacement behaviour may be congruent in capturing the key stages in locking performance qualitatively as well as calculating the magnitude of reaction forces during the process.

[00078] In FIG. 7(b), movement in the locking direction may start from an initially undeformed and stress-free configuration. Similar to the mechanical behavior of the insertion process, the reaction force may increase approximately by 10 N due to the rigid body motion of teeth and elastic deformation of the flexible region as illustrated in FIG. 7(c). As can be seen in FIG. 7(d), the contact phenomena that may be occurring between the teeth and the vertical wall of the base platform located behind the teeth may result in a sharp increase in the reaction force. Further, motion in this direction may lead to resistance of the stiff wall impacting against the stiff teeth which may be restricted from sliding over one another due to their specific geometry features. This may result in the force escalating to a maximum of 60 N.

[00079] Finally, the flexible material may fail after experiencing approximately 120% of strain. Although material failure may not be considered in finite element simulations, the occurrence of failure may be observed during the physical experiments. As seen in FIG. 7(e), the force may decrease largely from its peak value of 60N after the failure of flexible region. Accordingly, failure of the flexible material may equate to the termination of the locking performance of the multi-material ratchet-like mechanism.

[00080] Furthermore, from the experimental study, it may be observed that failure may occur in the location of maximum stress in the soft material rather than at the interface between two different printed materials. This may be likely due to the strong interface bonding between stiff and soft printed material as both of these materials are acrylate -based and three-dimensional (3D) printing process may result in chemical bonding at the interface.

[00081] The results presented in FIG. 6 and FIG. 7 may illustrate the fundamental mechanical behaviours of the multi-material ratchet-like mechanism according to various embodiments during insertion and locking sequences. As predicted, the geometric design of the teeth, coupled with the embedded flexible region, may cause an ease in motion for the insertion direction with less resisting reaction force (16 N for the samples in FIG. 6) in comparison to the opposite direction (maximum of 60 N pull-out force for the samples in FIG. 7). Furthermore, it should be noted that the examples and the results presented in FIG. 6 and FIG. 7 are just one instantiation of the various embodiment, and if one have other constraints, such as a desire for smaller relative displacement between teeth or a limitation of maximum force during insertion or locking, the geometric and material parameters may be changed to fulfil the desired criteria.

[00082] Various embodiments may be tailored for different applications through modifying the geometrical or material parameters. One such parameter that may have an impact on the mechanical behaviour may be the elastic modulus of the material in the embedded flexible segment. This may be important as the flexible region is responsible for transferring the displacement of stiff parts to local elastic deformations in both the insertion and locking performances, which is reflected in FIG. 6(e) and FIG. 7(e), where the maximum elastic strains in the flexible region during insertion and locking process are illustrated.

[00083] FIG. 8 shows results of a parametric study conducted by varying the elastic modulus of the flexible region to determine its effect on maximum reaction force during insertion and locking processes. The maximum reaction forces during insertion are shown by line 801 and maximum reaction forces during locking are shown by line 803.

[00084] FIG. 8 illustrates that by decreasing the elastic modulus of the flexible material by using softer materials may result in a reduction in required force for insertion and also a decrease in the resisting force during the locking process. This may be especially prevalent in the locking motion as increasing the stiffness of flexible material by 100% may result in the increasing of the required force for insertion by 65% while the resistance force in the locking direction may increase 100%. Therefore, varying the material properties of the flexible material may be a suitable approach to control the behaviour of the multi-material ratchet-like mechanism for different specific applications.

[00085] In addition to the elastic modulus, the failure strain of the material may affect the performance. As discussed previously, the termination point of interlocking may be due to the failure of flexible material after experiencing approximately 120% elastic strain. Therefore, improvement of the locking performance may be through the usage of other elastomers with higher failure strains.

[00086] According to the various embodiments, the geometric parameters may also have an impact on the force-displacement response during insertion and locking motions. This may be observed from the parametric study and the analysis on the geometric parameters, which may allow tailor for various applications according to specific needs based on an understanding of how to control the behaviour. The finite element model may be used to perform the parametric analysis. FIG. 9 shows the results of a parametric study showing the relationship between the reaction forces to the geometric parameters: FIG. 9(b) Thickness of flexible region (ti); and FIG. 9(c) Angle of the wedge (& ). Line 901 represents insertion and line 903 represent locking

[00087] As shown in FIG. 9(b), the thickness of the flexible material may be one of the factors controlling the force during insertion and locking motions. This is because the flexible region may experience lower elastic strains in the samples with thicker flexible regions. The increase in thickness of flexible material may ease the insertion process by decreasing the force required for insertion. On the other hand, although this increase may not have a significant impact on the locking performance for up to 3.0 mm of flexible material thickness, further increase of this parameter may have a negative effect on the locking performance as the pull-out force may decrease significantly when the thickness goes beyond 3.0 mm. Therefore, appropriate value may be picked for this parameter with respect to the desired application.

[00088] FIG. 9(c) presents the changes in reaction force during insertion and locking steps in relation to different angles of teeth as one of the geometric parameters. It can be seen in FIG. 9(c) that the required force for insertion may increase slightly by increasing the wedge angle of teeth. However, by increasing the angle more than 25°, the trend may change and the insertion force may increase exponentially. This may be because of an increased bending and motion from teeth for these angles and therefore there may be more resistance during insertion from supporting walls behind the teeth. [00089] Furthermore, it can also be seen in FIG. 9(c) that although the provided locking force may be independent of changes of wedge angle of teeth from 30° to 15°, for lower angles the resisting force may increase dramatically. This may be due to the changes in the structure of the mechanism. For an angle of teeth higher that 15°, the teeth may begin to slide downwards during the locking mechanism after reaching the support wall behind them. While for angles lower than 15°, the teeth may not slide down and may make a surface to surface constraint against supporting wall that may increase the resistance force dramatically.

[00090] The other geometrical parameter that may affect the locking performance may be the shape of the supporting wall. As described above, the tooth may start sliding down after contacting the supporting wall during the locking performance. However, the specific changes made on the supporting wall geometry may resist this sliding phenomenon and as a result, may increase the resisting force in locking direction. This effect may be achieved by applying a simple geometric change as shown in FIG. 3.

[00091] FIG. 3 shows that the modification of the supporting wall may include creating a step feature on the supporting wall. According to an implementation, a maximum resisting force for an embodiment with the modified stepped wall reaches around 900 N which is around 13 times more than the resisting force for an embodiment without the modified stepped wall. Moreover, the step feature may eliminate the sliding phenomenon between the tooth and supporting wall which affects the force-displacement behaviour. In the embodiment with the modified stepped wall, the force may increase dramatically after the tooth contacts the supporting wall and the soft material may not fail. However, in the embodiment without the modified stepped wall, the soft material may tear after sliding of tooth over supporting wall and this may cause the drop in the force.

[00092] Moreover, as surface sliding is one of the main factors of the mechanism, the smoothness of the contact surfaces may also be a parameter in controlling the behaviour. Therefore, it may be possible to reduce the insertion force by reducing the friction coefficient of top surfaces of teeth, while at the same time more resistance in locking direction may be possible if the vertical surface of teeth and supporting wall (see FIG. 9(a)) surfaces are made coarser.

[00093] As described above, the geometrical parameters may have a significant effect on the behaviour of the multi-material ratchet-like mechanism. Accordingly, the choice of the parameters may be dependent on the application, scale, and the fabrication method. For example, modifying the support wall with an added step may improve the locking performance. The fabrication of this geometrical feature at a small scale may require a fabrication method that may be able to handle high-resolutions.

[00094] According to various embodiments, an array configuration with multiple teeth may be tailored with desired mechanical performance for various applications. According to various embodiments, the analytical results from a single tooth configuration may be used to predict the mechanical behaviour of the array configuration. To elaborate the behaviour of this configuration, each set of teeth is one mechanism which may be assumed to work as a nonlinear spring with a specific stiffness matrix. In the simple case where teeth are only acting against each other, the array of teeth may be analyzed as parallel springs because each of them may resist against the same applied displacement at the same time. If n is the number of sets that are fitted and used together to create a new sample and the stiffness of each of them is K then the stiffness of the mechanism is predicted to be nK. Therefore, the mechanism in an array configuration containing n teeth may exhibit n times more resistance in comparison to one single mechanism. FIG. 10(a) shows the schematic of connection between the mechanical performances of a single-cell configuration with the multi-cell configuration. FIG. 10(b) and FIG.10(c) show the comparison of the force- displacement behaviour of the single unit cell, and three sets array configuration for: FIG. 10(b) the insertion direction, and FIG. 10(c) the locking direction.

[00095] FIG. 10 also illustrates the comparison of results from finite element analysis for a single set sample and an array configuration including three sets of teeth as an example of multi-cell configuration. As can be seen in FIG. 10(b) and FIG. 10(c), increasing the number of sets may increase the reaction forces during insertion and locking steps linearly. Accordingly, various embodiments may be tailored for a specific application by combining different numbers of sets of teeth.

[00096] Various embodiments have provided a multi-material ratchet-like mechanism configured to integrate the principles of compliant mechanism and classical ratchet mechanisms. The multi-material ratchet- like mechanism may allow the motion of parts in one direction while resisting the motion in the opposite direction. This behaviour may be achieved by transferring the displacement of parts to elastic deformation in the flexible region during the insertion step while using the ratchet tooth geometry to restrict the motion of the parts in the opposite direction. Advantageously, various embodiments may eliminate the need of discrete elements, e.g. springs, thus reduce of the part count as compared to classical ratchet mechanisms. Various embodiments may also reduce the space required for the global perpendicular motion of pawls (which is required in classical ratchet mechanisms) during insertion. Further, various embodiments may have capability to control the mechanical behaviour by tuning material properties, material layout, and geometry.

[00097] Furthermore, the force-displacement behaviour of the various embodiments may be controlled via altering the elastic modulus of the flexible material, the thickness of compliant region, the angle of the wedge, and the geometry of the supporting wall. For example, the effect of altering the elastic modulus of flexible region may be more dominant in the locking motion than in insertion motion. The increases in thickness of flexible region may help the insertion process while having limited effects on locking direction for up to 3.0 mm in our configuration. The wedge angle of teeth may perform well for both directions only within a limited range of value.

[00098] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes, modification, variation in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

1. A multi-material ratchet- like mechanism comprising:

a first body;

a second body interfacing with the first body;

a first interlocking element which extends from a portion of the first body and which comprises a first compliant mechanism between the portion of the first body and a tip portion of the first interlocking element; and

a second interlocking element which extends from a corresponding portion of the second body and which comprises a corresponding tip portion,

wherein the tip portion of the first interlocking element is configured to cause elastic deformation of the first compliant mechanism so as to slide the tip portion of the first interlocking element over the corresponding tip portion of the second interlocking element when engaging in the first direction, and is further configured to lock against the corresponding tip portion of the second interlocking element when engaging in the second direction,

wherein the first interlocking element is a continuous structure, and

wherein the first compliant mechanism and the tip portion of the first interlocking element are made of different materials.

2. The mechanism as claimed in claim 1, wherein the second interlocking element comprises a second compliant mechanism between the corresponding portion of the second body and the corresponding tip portion of the second interlocking element, wherein the second interlocking element is a continuous structure, and wherein the second compliant mechanism and the corresponding tip portion of the second interlocking element are made of different materials.

3. The mechanism as claimed in claim 2, wherein the corresponding tip portion of the second interlocking element is configured to cause elastic deformation of the second compliant mechanism when engaging the tip portion of the first interlocking element in the first direction, and is further configured to lock against the tip portion of the first interlocking element when engaging in the second direction.

4. The mechanism as claimed in any one of claims 1 to 3, wherein the first direction is opposite the second direction.

5. The mechanism as claimed in any one of claims 1 to 4, wherein the tip portion of the first interlocking element is of a higher stiffness than the first compliant mechanism.

6. The mechanism as claimed in any one of claims 2 to 5, insofar as they depend on claim 2, wherein the corresponding tip portion of the second interlocking element is of a higher stiffness than the second compliant mechanism.

7. The mechanism as claimed in any one of claims 1 to 6, wherein the tip portion of the first interlocking element comprises a stop surface and a slide surface angled relative to the stop surface, wherein the stop surface of the tip portion of the first interlocking element is at least substantially perpendicular to the second direction when the first compliant mechanism of the first interlocking element is in an undeformed state.

8. The mechanism as claimed in any one of claims 1 to 6, wherein the tip portion of the first interlocking element comprises a stop surface and a slide surface angled relative to the stop surface, wherein the stop surface of the tip portion of the first interlocking element is inclined relative to the second direction when the first compliant mechanism of the first interlocking element is in an undeformed state.

9. The mechanism as claimed in claim 7 or 8, wherein the slide surface of the tip portion of the first interlocking element is angled less than 90 degrees with respect to the stop surface of the tip portion of the first interlocking element.

10. The mechanism as claimed in any one of claims 2 to 9, insofar as they depend on claim 2, wherein the corresponding tip portion of the second interlocking element comprises a corresponding stop surface and a corresponding slide surface angled relative to the corresponding stop surface, wherein the corresponding stop surface of the corresponding tip portion of the second interlocking element is at least

substantially perpendicular to the second direction when the second compliant mechanism of the second interlocking element is in an undeformed state.

11. The mechanism as claimed in any one of claims 2 to 9, insofar as they depend on claim 2, wherein the corresponding tip portion of the second interlocking element comprises a corresponding stop surface and a corresponding slide surface angled relative to the corresponding stop surface, wherein the corresponding stop surface of the corresponding tip portion of the second interlocking element is inclined relative to the second direction when the second compliant mechanism of the second interlocking element is in an undeformed state.

12. The mechanism as claimed in claim 10 or 11, wherein the corresponding slide surface of the corresponding tip portion of the second interlocking element is angled less than 90 degrees with respect to the corresponding stop surface of the

corresponding tip portion of the second interlocking element.

13. The mechanism as claimed in any one of claims 10 to 12, insofar as they depend on claim 7 or 8, wherein, when engaging the first interlocking element and the second interlocking element in the first direction, the slide surface of the tip portion of the first interlocking element and the corresponding slide surface of the corresponding tip portion of the second interlocking element are configured to bear flat against each other to cause the elastic deformation of the respective first and second compliant mechanisms such that the slide surface of the first interlocking element and the corresponding slide surface of the second interlocking element are oriented at least substantially parallel to the first direction so as to slide over each other.

14. The mechanism as claimed in any one of claims 10 to 13, insofar as they depend on claim 7 or 8, wherein, when engaging the first interlocking element and the second interlocking element in the second direction, the stop surface of the tip portion of the first interlocking element and the corresponding stop surface of the

corresponding tip portion of the second interlocking element are configured to bear flat against each other so as to lock against each other to prevent relative movement in the second direction.

15. The mechanism as claimed in any one of claims 1 to 14, wherein the first body comprises a recess and the first interlocking element extends from a base portion of the recess.

16. The mechanism as claimed in claim 15, wherein the tip portion of the first interlocking element protrudes out of the recess of the first body.

17. The mechanism as claimed in claim 15 or 16, wherein an inner wall portion of the recess immediately adjacent to the stop surface of the first interlocking element comprises a chamfered edge at a rim portion of the recess.

18. The mechanism as claimed in any one of claims 15 to 17, wherein a further inner wall portion of the recess immediately adjacent to an opposite side of the stop surface of the first interlocking element comprises a step at a base edge of the further inner wall portion.

19. The mechanism as claimed in any one of claims 15 to 18, insofar as they depend on claim 2, wherein the second body comprises a corresponding recess and the second interlocking element extends from a corresponding base portion of the corresponding recess.

20. The mechanism as claimed in claim 19, wherein the corresponding tip portion of the second interlocking element protrudes out of the corresponding recess of the second body.

21. The mechanism as claimed in claim 19 or 20, wherein a corresponding inner wall portion of the corresponding recess immediately adjacent to the corresponding stop surface of the second interlocking element comprises a corresponding chamfered edge at a corresponding rim portion of the corresponding recess.

22. The mechanism as claimed in any one of claims 19 to 21, wherein a corresponding further inner wall portion of the corresponding recess immediately adjacent to an opposite side of the corresponding stop surface of the second interlocking element comprises a corresponding step at a corresponding base edge of the corresponding further inner wall portion.

23. The mechanism as claimed in any one of claims 1 to 18, wherein the first compliant mechanism comprises a height of 5mm or less.

24. The mechanism as claimed in any one of claims 2 to 18, insofar as they depend on claim 2, wherein the second compliant mechanism comprises a height of 5mm or less.

25. The mechanism as claimed in any one of claims 7 to 9, wherein the slide surface of the first interlocking element is treated or machined or surface finished to reduce friction.

26. The mechanism as claimed in any one of claims 7 to 9 or 25, wherein the stop surface of the first interlocking element is treated or machined or surface finished to increase friction.

27. The mechanism as claimed in any one of claims 10 to 12, wherein the corresponding slide surface of the second interlocking element is treated or machined or surface finished to reduce friction.

28. The mechanism as claimed in any one of claims 10 to 12 or 27, wherein the corresponding stop surface of the second interlocking element is treated or machined or surface finished to increase friction.

29. The mechanism as claimed in any one of claims 1 to 27, wherein the first body comprises a plurality of the first interlocking elements and the second body comprises a plurality of the second interlocking elements.