GB2577536A

GB2577536A - Droplet actuation

Info

Publication number: GB2577536A
Application number: GB1815819.6A
Authority: GB
Inventors: Ma Hanbin; Su Yang; Nathan Arokia
Original assignee: Acxel Tech Ltd
Current assignee: Acxel Tech Ltd
Priority date: 2018-09-28
Filing date: 2018-09-28
Publication date: 2020-04-01
Also published as: GB201815819D0; GB2578187B; GB2577607B; GB201911168D0; CN109603931B; GB2577607A; GB201911169D0; GB2578187A; CN109603931A

Abstract

A method of forming an electrowetting-on-dielectric droplet actuation device comprising one or more faces, the method comprising using an additive manufacturing process, disposing a non-conductive material to form a substrate 3 and a microfluidic structure 16 surrounding the substrate, a conductive material to form an array of connectors 12 and electrodes 8 within the substrate and a dielectric and hydrophobic material to form a layer 15 covering the electrodes and substrate, and disposing a lid 23 having a first 24 and second 25 side onto the microfluidic structure and over the electrodes leaving a space, wherein the second side of the lid has a conductive material coating and a hydrophobic material coating and the second side of the lid faces the array of electrodes. A method as above further characterized by a dielectric and hydrophobic material to form a functional structure over the first dielectric and hydrophobic layer. The additive manufacturing process may comprise any of multilateral direct-ink-writing, selective laser sintering, stereolithography, fused filament fabrication or extrusion based 3D printing. An electrowetting-on-dielectric droplet actuation device and an electro-wetting droplet manipulation device.

Description

Droplet actuation

Field of the Invention

The present invention relates to a method of forming an electrowetting-on-dielectric droplet actuation device.

Background

Electrowetting-on-dielectric (EWOD) is a unique technique in digital microfluidics for lab-on-a-chip (LoC) systems which have the potential to manipulate small volumes of so liquid samples, also referred to as "droplets". An EWOD device could be served as a front-up platform to perform complex sample handling procedures for other LoCs.

An introduction to electrowetting is given in F. Mugele and J. C. Baret: "Electrowetting: from basics to applications", Journal of Physics: Condensed Matter, volume 17, page R705 (2005) and an overview of electrowetting-on-dielectric devices is given in W. Nelson & C-J Kim: "Droplet Actuation by Electrowetting-on-Dielectric (EWOD): A Review", Journal of Adhesion Science and Technology, volume 26, pages 1747-1771 (2012), which are incorporated herein by reference.

The key obstacle for EWOD development is the complex manufacturing processes, which requires fabrication steps for both micro-electronics and micro-fluidics. In order to activate the electrowetting effect, conductive electrodes need to be seamlessly integrated into microfluidics devices with selected dielectric layer and hydrophobic layer. The embedded electrodes are also required to connect with external driving electronics, and the connection also needs to be carefully designed to minimize the influence of the microfluidics structures.

Summary

According to a first aspect of the invention there is provided a method of forming an electrowetting-on-dielectric droplet actuation device comprising one or more faces. The method comprises using an additive manufacturing process to dispose a non-conductive material to form a substrate and a microfluidic structure surrounding the substrate; a conductive material to form an array of connectors and electrodes embedded within the substrate; and a dielectric and hydrophobic material to form a layer covering the electrodes and substrate. The method further comprises disposing a lid having first and second sides onto the microfluidic structure and over the electrodes leaving a space. The second side of the lid has a conductive material coating and a hydrophobic material coating and the second side of the lid faces the array of electrodes.

The method may further comprise using an additive manufacturing process to dispose a dielectric and hydrophobic material to form a functional structure over the dielectric and hydrophobic layer.

According to a second aspect of the invention there is provided a method of forming an electrowetting-on-dielectric droplet actuation device comprising a functional structure.

The method comprises using an additive manufacturing process to dispose a nonconductive material to form a substrate and a microfluidic structure surrounding the substrate; a conductive material to form an array of connectors and electrodes embedded within the substrate; a dielectric and hydrophobic material to form a first dielectric and hydrophobic layer covering the electrodes and substrate. The method -0 or further comprises disposing dielectric and hydrophobic material to form the functional structure over the first dielectric and hydrophobic layer. The method further comprises disposing a lid having first and second sides layer onto the microfluidic structure and the functional structure and over the electrodes leaving a space. The second side of the lid has a conductive material coating and a hydrophobic material coating and the second side of the lid faces the array of electrodes.

The additive manufacturing process may comprise multilateral direct-ink-writing. At least part of the additive manufacturing process may comprise selective laser sintering (SLS). At least part of the additive manufacturing process may comprise stereolithography (SLA). At least part of the additive manufacturing process may comprise fused filament fabrication (FFF). At least part of the additive manufacturing -3 -process may comprise extrusion-based 3D printing and the like. The additive manufacturing process may comprise a combination of these processes. The additive manufacturing process may comprise other additive manufacturing processes.

During the additive manufacturing process, each material may be disposed either concurrently or consecutively. Some materials may be disposed consecutively and some materials may be disposed concurrently.

The non-conductive material, the conductive material and the dielectric and hydrophobic material may each be disposed using a plurality of nozzles. Each of the plurality of nozzles may be configured to deposit a different material. Any number of the plurality of nozzles may be configured to deposit the same material.

The method may dispose a plurality of faces. The faces may be configured to allow one or more droplet(s) to move between the spaces of adjacent faces. At least one face may be on a different plane to another face. The plurality of faces may form a box-like structure.

According to a third aspect of the invention there is provided an electrowetting-on-dielectric droplet actuation device. The device comprises a plurality of faces. Each face comprises an array of electrodes; a dielectric and hydrophobic layer covering the electrodes and a lid having first and second sides disposed over the electrodes leaving a space. The faces configured to allow one or more droplet(s) to move between the spaces of adjacent faces. At least one face is on a different plane to a second face. -0or

One or more electrode(s) may have a dielectric and hydrophobic material forming a functional structure disposed over the dielectric and hydrophobic layer over the electrode.

The device may further comprise a substrate having a first side and a second side, and connectors connected to each electrode. The electrodes may be positioned to be flush to the first side of the substrate and the connectors may be positioned to be flush to the second side of the substrate. The device may further comprise a microfluidic structure surrounding the perimeter of the substrate, flush to the second substrate side and extending past the first substrate side. The dielectric and hydrophobic layer may cover the electrodes and the first side of the substrate. The second side may have a conductive -4 -material coating and a hydrophobic material coating. The second side of the lid may face the array of electrodes.

The connectors may be connected to driving electronics.

A physical wall made from a dielectric and hydrophobic material may be disposed on the first side of the substrate, in between electrodes to make a physical barrier between electrodes.

/0 The faces may be configured to form a box-like structure. The plurality of faces may form one or more monolithic layers.

The faces may be configured to form any three-dimensional shape.

The driving electronics may be inside the box-like structure. The driving electronics may be outside the box-like structure. The driving electronics may be both inside and outside the box-like structure.

The substrate of the device may be sheet-like.

The substrate is longer in first and second perpendicular axes than it is in a third axis extending perpendicular from the plane of the first two axes.

The device may be generally square. -0or

The electrodes may be square.

The electrodes may be hexagonal.

The electrodes may be any tessellating shape. The array of electrodes may be tessellated.

The first functional structure may be in the centre of a row or column of three electrodes. -5 -

The second functional structure may be in the centre of a row of electrodes forming the top bar of a T shape.

The third functional structure may be in the centre of five electrodes forming a cross shape.

The lid may be transparent or opaque.

A first face of the device may be at a right angle from the second face of the device.

According to a fourth aspect of the invention, there is provided an electrowetting-ondielectric droplet manipulation device. The device comprises an electrode, a first dielectric and hydrophobic layer covering the electrode and a lid disposed over the electrode leaving a space. The device further comprises a second dielectric and hydrophobic layer forming a functional structure over the electrodes, interposed between the first dielectric and hydrophobic layer and the lid.

At least one functional structure may be a first functional structure in the shape of first and second semi-circles with first and second straight edges positioned alongside opposite electrode edges.

At least one functional structure may be a second functional structure in the shape of a triangle having first and second corners adjacent to an edge of an electrode and a third corner over the centre of the electrode. -0or

At least one functional structure may be a third functional structure in the shape of a four pointed star having tips of the star close to or at the edges of an electrode. -6 -

Brief Description of the Drawings

Certain embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a first electrowetting-on-dielectric device; Figures 2A to 2D are perspective views illustrating electrowetting-on-dielectric device manufacture; Figures 3A to 3D are cross sections illustrating electrowetting-on-dielectric device manufacture; Figure 4 illustrates functional structure manufacture; o Figure 5 is a plan view of a pixel array including first, second and third functional structures; Figure 6 is a cross-section view illustrating a first functional structure pixel; Figures 7A to 7D are plan views illustrating a first functional structure pixel array; Figures 8A to 8D are plan views illustrating a second functional structure pixel array; Figures 9A to 9D are plan views illustrating a third functional structure pixel array; Figure in is a plan view illustrating a droplet inlet; Figure 11 is a plan view illustrating sample storage; Figure 12 is a perspective view illustrating a second electrowetting-on-dielectric device; Figure 13 is a cross-sectional view illustrating a second electrowetting-on-dielectric device; Figure 14 is an exploded perspective view illustrating a second electrowetting-ondielectric device; Figure 15 is a perspective view illustrating a third electrowetting-on-dielectric device; Figure 16 is a cross-sectional view illustrating a third electrowetting-on-dielectric 25 device; Figure 17 is an exploded perspective view illustrating a third electrowetting-ondielectric device; Figure 18 is a perspective view illustrating a fourth electrowetting-on-dielectric device; Figure 19 is a cross-sectional view illustrating a fourth electrowetting-on-dielectric device; Figure 20 is an exploded perspective view illustrating a fourth electrowetting-ondielectric device;

Detailed Description of Certain Embodiments

Electrowetting-on-dielectric device 1 -7 -Figure 1 provides a cross-sectional view of a first additive manufactured electrowettingon-dielectric (EWOD) device 1 capable of moving a droplet 2. The electrowetting-ondielectric device 1 generally takes the form of a substrate 3 having first and second sides 4, 5 and a perimeter 6. The substrate 3 is longer in a first and a second perpendicular major axes than it is in a third axes perpendicular to the plane of the first and second axes.

An array of electrodes 8 are inset on the first side 4 of the substrate 3. Each electrode 8 has a front 9 and a back 10. The front 9 of each electrode may be flush to the first side 4 of the substrate 3. The electrodes 8 are connected to driving electronics 12 by connectors 13 which are attached to the back 10 of the electrodes 8. The connectors 13 pass from the back 10 of the electrodes 8 through to the second side 5 of the substrate 3. Each connection 13 may be flush to the second side 5 of the substrate 3. Each electrode 8 connected to a corresponding connector 13 and driving electronics 12 is herein also referred to as a "pixel" 14.

A dielectric and hydrophobic layer 15 is disposed onto the first side 4 of the substrate 3 and the front 9 of the electrodes 8. A microfluidic structure 16 is placed adjacent to the perimeter 6 of the substrate 3 from the second side 5 of the substrate 3, and extends past the dielectric and hydrophobic layer 15. The microfluidic structure 16 has a first and a second side 17,18. A lid 23 having first and second sides 24, 25 is disposed on the microfluidic structure so that the second side 25 of the lid 23 is adjacent to the first side 17 of the microfluidic structure 16.

The lid comprises a material that can be used as a substrate in the field of semiconductors. For example, the lid may comprise any one of, or any combination of poly(methyl methacrylate) (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS) or polyimide (PI), etc. The lid may comprise a glass material. The second side 25 of the lid 23 is coated with a conductive material and a hydrophobic material. The conductive material may also be hydrophobic.

The conductive material may be opaque or transparent. The conductive material may be a transparent conductive oxide (TCO). The conductive material may be cadmium-tin oxide (CTO). The conductive material may be indium-tin oxide (ITO). The hydrophobic material coating the second side 25 of the lid 23 may be a fluoric material. The hydrophobic material may be polytetrafluoroethylene (PTFE or Teflon ni) or CYTOP TM. -8 -

The second side 25 of the lid 23 is placed on the first side 17 of the microfluidic structure 16 leaving a space 3o for a droplet 2 to move through. The driving electronics 12 and the conducting coating of the lid 23 are connected to ground 31.

The electrowetting-on-dielectric device 1 may be of any shape. The device 1 may have a generally square, rectangular, hexagonal, octagonal or circular shape. The device 1 may have an irregular shape. The device 1 may have a shape with any number of sides. The device 1 may be any size. Typically, the device 1 may have a size in the order of millimetres, optionally from about 20 mm to i000 mm along any major axes. For example, the device 1 may be 20 MM x 200 mm, 120 mm x 200 mm or 200 MM x 200 mm, but it may also be 400 mm x moo mm, or woo mm x woo mm.

The electrowetting-on-dielectric device 1 may have an array of any number of 15 electrodes 8. The array may have hundreds of electrodes 8. The array may have thousands of electrodes 8. The array may have more than thousands of electrodes 8. The array may have more than ten thousand electrodes 8.

Referring to Figures 2A to 2D, a first electrowetting-on-dielectric device 1, is generally square or rectangular in shape. The device 1, has an array of sixteen electrodes 8 arranged in a grid of four rows and four columns. The microfluidic structure 16 forms a wall around the array of electrodes, providing a physical barrier to prevent droplets 2 from escaping the device Each electrode 8 may be any shape. Each electrode 8 may have a generally square, rectangular, hexagonal, octagonal or circular shape. Each electrode 8 may have an irregular shape. The device may have a shape with any number of sides. Each electrode 8 is generally flat and thin, having a greater length in a first and a second major axes than in a third axis perpendicular to the plane of the first and second major axes. Each electrode may be square or rectangular or hexagonal. Each electrode may be a regular or irregular shape. Each electrode may have any number of sides.

The size of the electrodes 8 will depend on a volume of each sample to be manipulated. Typically, each electrode 8 may have a size in the order of micrometres to millimetres, 35 optionally from about loo pm to 10 mm along any major axis. For example, each -9 -electrode 8 may be 100 pm x 200 pm or 200 pm x 400 pm, but it may also be 100 pm x to mm, or lo mm x to mm.

Each array of electrodes 8 may have electrodes 8 of the same shape and size. Each array 5 of electrodes 8 may have a combination of electrodes 8 having different shapes and sizes. The electrodes 8 in an array may be tessellated.

The distance between the edges of electrodes 8 is to avoid unwanted electrical connections between electrodes 8. The distance between the edges of adjacent o electrodes 8 is typically very small. The distance between the edges of adjacent electrodes 8 may be 25.4 pm. The distances between the edges of adjacent electrodes 8 within an array may be the same. The distances between the edges of adjacent electrodes 8 within an array may vary.

Referring to Figures 2A to 3D, the manufacture of an electrowetting-on-dielectric device 1 is performed additively. An additive manufacturing (AM) process may comprise multilateral direct-ink-writing, selective laser sintering (SLS), stereolithography (SLA) and fused filament fabrication (FFF) or extrusion-based 3D printing and the like. A plurality of nozzles 35 may be used to deposit material or materials in a particular configuration to make the electrowetting-on-dielectric device 1. The material may include, for example, non-conductive material, conductive material and dielectric and hydrophobic material. There may be any number of nozzles depositing any number of different materials either consecutively or concurrently. Using this method, the conductive electrodes and supporting microfluidics structures in EWOD can be constructed with little effort.

Referring particularly to Figures 2A and 3A, a first nozzle 33, may deposit a nonconductive material as a substrate 3, leaving spaces for an array of connectors 13 to be deposited by a second nozzle 352. which delivers a conductive material. Referring particularly to Figures 2B and 3B, an array of electrodes 8 are deposited by the second nozzle 352. vvhich delivers a conductive material. Further non-conductive material is added to the substrate to make the first side 4 of the substrate 3 flush with the front 9 of the electrodes 8. Referring particularly to Figures 2C and 3C, a first dielectric and hydrophobic layer 15 is then added to the first side of the substrate 4 and the front 9 of the electrodes 8 by a third nozzle 353 which delivers a dielectric and hydrophobic material. Referring particularly to Figures 2D and 3D, the microfluidic structure 16 is -10 -then added around the substrate 3 so that it touches the substrate perimeter 6 using a fourth nozzle 354 which delivers non-conductive material.

Referring to Figure 4, additional functional structures 36 can be added to an electrode 8. The functional structure 36 is made from a dielectric and hydrophobic material. A nozzle 35 may deposit the dielectric and hydrophobic material on top of the first dielectric and hydrophobic material layer 15 generating a functional structure 36 which may be used to manipulate a droplet 2. The functional structure 36 may be attached to the first dielectric and hydrophobic material layer 15 or it may be floating above it. The functional structure 36 may be in a fixed position or may be able to move on the electrode 8. A physical wall 37 also made from the dielectric and hydrophobic material can also be added around a group of electrodes 8 in an array to prevent the movement of a droplet 2 passing to certain adjacent electrodes 8. Such a wall 37 may be used to contain droplets 2 prior to being manipulated elsewhere on the electrowetting-on-dielectric device 1.

Referring to Figure 5, a first functional structure 36, is formed in the shape of first and second semi-circles 38,, 382, each having a curved edge 39 and a straight edge 4o. The curved edges 39 are placed towards the centre of the electrode 8. The electrode 8 is square or rectangular and has first, second, third and fourth edges 41,, 412, 413, 414. The straight edges 4o of the first and second semi-circles 38,, 38,, of the first functional structure 36, are placed close to or abutting opposite edges 412, 414 of an electrode 8. A second functional structure 362 is formed in the shape of a triangle structure having two corners adjacent to an edge 41 of an electrode 8, and a remaining corner in the centre of the electrode 8. A third functional structure 363 is formed in the shape of a four pointed star having tips of the star close to or at the edges 41 of the electrode 8. As will be explained in more detail later, all three functional structures 36 allow for droplets 2 to be split into two while being actuated through the electrode 8 array.

Referring to Figure 6, a cross-sectional view of an electrode 8 having the first functional structure 36, deposited on the first dielectric and hydrophobic material layer 15. The space 3o through which a droplet 2 can move has reduced in size.

Referring to Figures 7 to 11, the electrodes 8 can be in an active or inactive state. In an active state the electrode 8 of the electrode 8 may have, for example, a positive bias applied. In an inactive state, the electrode 8 may be, for example, floating, or grounded.

Generally, electrodes 8 in an inactive state will be grounded. When an electrode 8 is in an active state, a droplet 2 will cover the area of the first dielectric and hydrophobic material layer 15 next to the electrode 8. If two or more adjacent electrodes 8 are active, the droplet 2 covers the area of the first dielectric and hydrophobic material layer 15 next to all adjacent active electrodes 8.

Referring to particularly to Figures 7A to 7D, a droplet 2 may be manipulated and split into first and second droplets 21, 2, using three electrodes 8b 8,, 83 in a row or column. In such an arrangement, the centre electrode 82 has the first functional structure 36,.

/0 The adjacent electrodes 8b 83 are positioned alongside opposite edges 41,, 413 of the centre electrode 82. When considering the three electrodes 8, 82, 83 together, such an arrangement forms a space 3o having a flat hour-glass-like shape.

Referring particularly to Figure 7A, a droplet 2 is held at the first electrode 8, which is active. The second and third electrodes 82, 83 are inactive. Referring particularly to Figure 7B, activating the second electrode 82 makes the droplet 2 cover the area of both first and second electrodes 8, 82. The droplet 2 is partially forced through the narrower space 30 created by the first functional structure 36, on the second electrode 82. Referring particularly to Figure 7C, activating the third electrode 83 makes the droplet 2 cover the area of all three electrodes 8,, 8,, 83 and appears pinched in the middle.

Referring particularly to Figure 7D, turning the second electrode 82 to the inactive state, while the first and second electrodes 8,, 83 remain active, makes the droplet 2 split into first and second droplets 2, 22.

Referring particularly to Figures 8A to 8D, a droplet 2 may be manipulated and split into first and second droplets 21, 2, using four electrodes 8,,, 8,2, 8,3, 8,4 arranged in a T configuration. A first electrode 8,, is at the base of the T, and second third and fourth electrodes 8,n, 8,3, 8,4 form a cross bar at the top of the T. The third electrode 8,3 in the T configuration is at the centre top of the T and has the triangular-shaped second functional structure 362. Referring particularly to Figure 8A, a droplet 2 is held on the first electrode 8,, which is active. Second, third and fourth electrodes 8,2, 8,3, 8,4 are inactive. Referring particularly to Figure 8B, activating the second electrode 8,2, makes the droplet 2 move to cover the areas of the first and second electrodes 8,, 8,2. The droplet 2 is now roughly oval in shape, but has been forced into the space 30 either side of the triangular-shaped second functional structure 36, on the third electrode 8,3.

Referring particularly to Figure 8C, deactivating the first electrode 8,, and activating -12 -the second and fourth electrodes 812, 8,4 moves the droplet 2 to spread across the top of the T bar, either side of the triangular-shaped second functional structure 362.

Referring particularly to Figure 8D, deactivating the third electrode 8,3 divides the droplet 2 into first and second droplets 21, 22 held on the second and fourth electrodes 812, 814 respectively.

Referring particularly to Figure 9A, a droplet 2 may be manipulated and split into first and second droplets z, 22 using five electrodes 821, 822, 823, 824, 825 arranged in a cross configuration. The central electrode 823, has the four pointed star shaped third functional structure 363. A droplet 2 starting on the first electrode 831 can be split into first and second droplets 21, 22 by activating the third electrode 823, moving the droplet 2 to cover the areas of both first and third electrodes 821, 823, making the droplet 2 cover either side of one of the points of the four pointed star functional structure 363. Deactivating the first electrode 821 and activating the second and fourth electrodes 822, 824 moves the droplet 2 to spread across the centre of the cross, either side of one of the points of the four pointed star-shaped third functional structure 363. Deactivating the third electrode 813 divides the droplet 2 into first and second droplets 21, 22 held on the second and fourth electrodes 812, 8,4 respectively. Referring to Figures 9B to 9D, this configuration of electrodes allows droplets 2 starting from any one of the outer electrodes 821, 822, 824, 825, to be manipulated and split into first and second droplets 21, 22.

Referring particularly to Figure to, a physical wall 37 made from a dielectric and hydrophobic material surrounds a square array of nine electrodes 8 arranged in three columns and three rows. The walled area has one entrance between the border of an entrance electrode 830 and an adjacent electrode 831. The walled area may be used, for example, to store larger droplets 45 for use elsewhere in the electrowetting-ondielectric device 1, or for sample storage. All electrodes 8 are active when storing a larger droplet 45. Smaller droplets 2 are split off from the larger droplet 45 by activating the adjacent electrode 83, moving a portion of the larger droplet 45 out of the walled area. Deactivating the entrance electrode 83o inside the walled area separates a droplet 2 from the larger droplet 45. Referring particularly to Figure 11, droplets 2 can be moved into the walled area and combined into the larger droplet 45 using the reverse operation.

-13 -A combination of functional structures 36, walls 37 and electrodes 8 can be used to sequentially or concurrently manipulate droplets 2 by moving, splitting or combining them. Functional structures 36 having similar shapes may be made on electrodes 8 having different shapes, for example, hexagonal or irregularly shaped electrodes 8.

Walls 37 may provide barriers at the edges 41 of electrodes 8 in any arrangement.

Referring to Figures 12 to zo, the droplets 2 can be moved in three dimensions. Manufacturing electrowetting-on-dielectric devices having several connected faces 5o, where at least one face 5o has a different plane to any other face 5o, allows three- /0 dimensional droplet actuation or movement. Manufacturing electrowetti ng-on-dielectric devices having several connected faces 5o at several orientations to form a box-like structure allows for droplets 2 to be moved vertically as well as horizontally. Each face so comprises all the features of the first electrowetting-on-dielectric device ti. The faces 5o may have a continuous space 3o, allowing droplet 2 transfers between them. The faces 5o may have independent spaces 3o having a physical barrier between them, preventing droplet 2 transfers from one face 5o to another.

Each face 5o may be of any shape and any size. Each face 5o may have an array of any number of electrodes 8. The array may have hundreds of electrodes 8. The array may 20 have thousands of electrodes 8. The array may have more than thousands of electrodes 8.

An electrowetting-on-dielectric device may also have several monolithic layer structures 51 (or "layer") within the box-like structure. Each layer comprises a substrate 3 with a first and a second side 4, 5. A first electrode 8 may be flush to the first side 4 and a second electrode 8 may be flush to the second side 5. The first and the second electrode may be at the same location on the substrate 3. A connector 13 connects the first electrode to the second electrode through the substrate 3. A hydrophobic and dielectric layer 15 is disposed on the electrodes and the first and second sides 4, 5 of the substrate 3. The monolithic layer structure 51 may have any orientation.

Having several faces 5o and/or layers 51 allows a user to perform different experiments simultaneously on the same device. The device may have any three-dimensional shape. The faces 51 may be at any angle from the layers 50. The faces 50 may be at right angles to the layers 51.

Referring particularly to Figures 12 to 14, a second electrowetting-on-dielectric device 1, 12 having first and second horizontal faces 50H,, 50112, and first and second vertical faces, 50v,, 50112. The first and second horizontal faces 50E,, 50E2 both have sixteen electrodes 8 arranged to have four rows and four columns. The first and second vertical faces 50v, 50v2 each have four electrodes 8 and are arranged in a single row.

The horizontal faces 50E, 50E2 are at right angles to the vertical faces, 50v, 50v2. The electrodes 8 of the first and second horizontal faces 50E1, 50E2 are oriented in the same direction. The electrodes 8 of the first and second vertical faces 50v, 50v2 are oriented in the opposite direction, facing away from each other. The driving electronics 12 are inside and outside the box-like structure. However, the driving electronics 12 may be inside and/or outside the box-like structure.

Referring particularly to Figure 13, a first and a second dot 2, 22 may be manipulated on different faces simultaneously.

The device 12 comprises first and second modules 54, 54,, 55, 551. The first module 54, comprises the first horizontal face 50H, and a microfluidic structure 16 extending up from the edges of the face 50E,. The second module 54, forms the second horizontal face 50E2 and the first and second vertical faces 50v, 50v2. The first and second modules 541, 551 are manufactured using the same additive method described earlier.

The microfluidic structure 16 supports the all the components of the device, and allows the space 30 for the droplet 2 to be formed. The microfluidic structure 16 may have a -0or solid or a hollow structure. Connections from the driving electronics 12 to a controlling system may be within a hollow structure of the microfluidic structure 16.

Referring particularly to Figure 14, the second electrowetting-on-dielectric device 12 is assembled by placing first and second vertical lids 23 at two opposite internal sides of 3o the microfluidic structure 16 of the first module 54,. Next, a first horizontal lid 23 is placed over the first dielectric and hydrophobic layer 15 of the first module 54,. The second module 55, is then inserted into the first module 54, and a second horizontal lid 23 is placed on top of the first side 17 of the microfluidic structure 16 of the first module 54, and the dielectric and hydrophobic layer 15 of the second module 551. The conductive material coating and the hydrophobic material coating on the second side -15 -of the lid 23 are connected to ground 31. The second side 25 of each lid 23 face the electrodes 8.

Referring to Figures 15 to 17, in a third electrowetting-on-dielectric device 1, 13, electrodes 8 may have different orientations on each face 50. A single electrode 8 may be on two faces 50, allowing the electrode 8 to be at a corner between two faces 50 having different planes. The third electrowetting-on-dielectric device 13 also comprises first and second modules 54, 542, 55, 552. The first module 542 comprises a generally square-shaped substrate 3, forming an approximately square-shaped base and a o microfluidic structure 16 extending at right angles from the plane of the substrate 3 from the perimeter 6 of the substrate 3.

The second module 552 comprises first and second horizontal faces 50113, 50114, and first and second vertical faces, 50v3, 50v4. The horizontal faces 50E3, 50114 are at right angles to the vertical faces, 50v3, 50^,4. The first and second horizontal faces 50E3, 50114 each have twenty-four electrodes 8 arranged in four rows and six columns. The central sixteen electrodes 8 in the first and second horizontal face 50113.50E4 are oriented in the opposite direction, with electrode faces 9 facing away from each other. The first and second vertical faces 50v3, 50v4 each have four electrodes 8 and are arranged in a single row. The electrodes 8 of the first and second vertical faces 50v3, 50v4 are oriented in the opposite direction, with electrode faces 9 facing away from each other.

The electrodes 8 on the outer columns of the first and second horizontal faces 50E3 50114 are right angled in shape, having a part of each electrode on an adjacent vertical -0or face 50v3, 50v4. The first and second modules 542, 552 are manufactured using the same additive method described earlier.

The driving electronics 12 are inside and outside the box-like structure. However, the driving electronics 12 may be inside and/or outside the box-like structure.

Referring particularly to Figure 17, the third electrowetting-on-dielectric device 13 is assembled by placing a first horizontal lid 23 over the substrate 3 of the first module 542. Next, first and second vertical lids 23 are placed at two opposite internal sides of the first module 542. The second module 552 is then inserted into the first module and a second horizontal lid 23 is placed on top of the first side 17 of the microfluidic structure 16 of the first module 542 and the dielectric and hydrophobic layer 15 of the second module 552. The conductive material coating and the hydrophobic material coating on the second side 25 of the lid 23 are connected to ground 31. The second side 25 of each lid 23 face the electrodes 8.

Referring to Figures 18 to 20, a fourth electrowetting-on-dielectric device 14, includes a first and a second layer 5E, 512, allowing a user to move a droplet 2 over and between layers 51. The fourth electrowetting-on-dielectric device 1, 14, comprises first, second and third modules 54b 553, 56.

The first module 543 includes a generally square shaped substrate 3 covered by a first horizontal lid 23, and a microfluidic structure 16 extending at right angles from the plane of the substrate 3 from the perimeter 6 of the substrate 3.

The second and third modules 553, 56 comprise first and second layers 5E, 512 respectively. Each layer 51 has first and second sides, 58, 59. Each layer 51 is similar in form and manufacture to the first electrowetting-on-dielectric device 12. However, each layer 511, 512 has electrodes inset to the substrate 3 on both the first and second substrate sides 4, 5. The dielectric and hydrophobic layer 15 covers both the first and second substrate sides 4, 5 and electrodes 8. Each layer 5E, 512, has thirty two electrodes, sixteen on the first side 58, and 16 on the second side 59. The electrodes 8 are arranged in four rows and four columns. A second horizontal lid 23 separates the space between twelve electrodes 8 on the second side 59 of the first layer 51, from twelve electrodes 8 on the first side 58 of the second layer 512. Both the first and second sides 24, 25 of the second horizontal lid 23 have a conductive material coating and a hydrophobic material coating.

All three modules may be manufactured using the additive technique described earlier. The driving electronics 12 are inside and outside the box-like structure. However, the driving electronics 12 may be inside and/or outside the box-like structure.

Referring particularly to Figure 20, the fourth electrowetting-on-dielectric device 14 is assembled by placing a first horizontal lid 23 over the substrate 3 of the first module 543. Next, the second module 553 is placed over the first horizontal lid 23, leaving a space 30 for a droplet 2 to move through. A second horizontal lid 23 is placed over the second side 59 of the first layer 51,, leaving a space 30. The third module 56 is placed over the second horizontal lid 23, leaving a space 30. A third horizontal lid 23 is then -17 -placed over the second side 59 of the second layer 5hand on the first side 17 of the microfluidic structure 16 of the first module 543. The conductive material coating and the hydrophobic material coating on the second side 25 of the first and third horizontal lids 23 are connected to ground. The second side 25 of the first and third horizontal lids 23 face the electrodes 8.

Modifications It will be appreciated that various modifications may be made to the embodiments hereinbefore described. Such modifications may involve equivalent and other features which are already known in the design, manufacture and use of electroweting-ondielectric or digital microfluidic devices and component parts thereof and which maybe used instead of or in addition to features already described herein. Features of one embodiment may be replaced or supplemented by features of another embodiment.

Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel features or any novel combination of features disclosed herein either explicitly or implicitly or any generalization thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention.

The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

-18 -Claims 1. A method of forming an electrowetting-on-dielectric droplet actuation device (1) comprising one or more faces (50), the method comprising: using an additive manufacturing process, disposing a non-conductive material to form a substrate (3) and a microfluidic structure (16) surrounding the substrate; a conductive material to form an array of connectors (12) and electrodes (8) embedded within the substrate; and a dielectric and hydrophobic material to form a layer (15) covering the electrodes and substrate; and disposing a lid (23) having first and second sides (24, 25) onto the microfluidic structure and over the electrodes leaving a space (3o); wherein the second side of the lid has a conductive material coating and a hydrophobic material coating; and the second side of the lid faces the array of electrodes.
2. The method of claim 1, the method further comprising: using an additive manufacturing process, disposing a dielectric and hydrophobic material to form a functional structure (36) over the dielectric and hydrophobic layer (15).
3. A method of forming an electrowetting-on-dielectric droplet actuation device 0) comprising a functional structure (36), the method comprising: using an additive manufacturing process, disposing a non-conductive material to form a substrate (3) and a microfluidic structure (16) surrounding the -0or substrate; a conductive material to form an array of connectors (12) and electrodes (8) embedded within the substrate; a dielectric and hydrophobic material to form a first dielectric and hydrophobic layer (15) covering the electrodes and substrate; and a dielectric and hydrophobic material to form the functional structure over the first dielectric and hydrophobic layer; and disposing a lid (23) having first and second sides (24, 25) layer onto the microfluidic structure and the functional structure and over the electrodes leaving a space (3o); wherein the second side of the lid has a conductive material coating and a hydrophobic material coating; and the second side of the lid faces the array of electrodes.
4. The method of any one of claim 1 to 3 wherein the additive manufacturing process comprises multilateral direct-ink-writing.
5. The method of any one of claim 1 to 4 wherein at least part of the additive manufacturing process comprises selective laser sintering.
6. The method of any one of claim 1 to 5 wherein at least part of the additive manufacturing process comprises stereolithography.
7. The method of any one of claim 1 to 6 wherein at least part of the additive manufacturing process comprises fused filament fabrication.
8. The method of any one of claim 1 to 7 wherein at least part of the additive manufacturing process comprises extrusion-based 3D printing.
9. The method of and one of claims 1 to 8 wherein each material is disposed concurrently.
10. The method of and one of claims 1 to 8 wherein each material is disposed consecutively.it The method of any one of claims 1 to 10 wherein the non-conductive material, the conductive material and the dielectric and hydrophobic material are each disposed using a plurality of nozzles (35)* 12. The method of claim ii wherein each of the plurality of nozzles is configured to deposit a different material.13. The method of claim ii wherein any number of the plurality of nozzles are configured to deposit the same material.14. The method of any one of claims 1 to 13 wherein there is a plurality of faces (50), the faces configured to allow one or more droplet(s) (2) to move between the spaces of adjacent faces; and at least one face is on a different plane to another face.15. The method of any one of claims 1 to 14 wherein the faces (50) form a box-like structure.16. An electrowetting-on-dielectric droplet actuation device (1) comprising: a plurality of faces (5o) wherein each face comprises: an array of electrodes (8); a dielectric and hydrophobic layer (15) covering the electrodes; a lid (23) having first and second sides (24, 25) disposed over the electrodes leaving a space (3o); the faces configured to allow one or more droplet(s) (2) to move between the spaces of adjacent faces; and wherein at least one face is on a different plane to a second face.17. The device according to claim 16 wherein one or more electrode(s) has a dielectric and hydrophobic material forming a functional structure (36) disposed over the dielectric and hydrophobic layer (15) over the electrode (8).18. The device according to claim 16 or 17, the device further comprising: a substrate (3) having a first side (4) and a second side (5); connectors (13) connected to each electrode (8), wherein the electrodes are positioned to be flush to the first side of the substrate and the connectors are positioned to be flush to the second side of the substrate; a microfluidic structure (16) surrounding the perimeter (6) of the substrate, flush to the second substrate side and extending past the first substrate side; wherein the dielectric and hydrophobic layer (15) covers the electrodes and the first side of the substrate; wherein the second side has a conductive material coating and a hydrophobic material coating; and the second side of the lid faces the array of electrodes.19. The device according to any one of claims 16 to 18 wherein the connectors are connected to driving electronics (12).20. The device according to any one of claims 16 to 19 wherein a physical wall (37) made from a dielectric and hydrophobic material is disposed on the first side (4) of the substrate (3), in between electrodes (8) to make a physical barrier between electrodes.-21 - 21. The device according to any one of claims 16 to 20 wherein the faces are configured to form a box-like structure.22. The device according to any one of claims 16 to 21 where in the plurality of faces form one or more monolithic layers (51).23. The device according to any one of claims 16 to 22 wherein the faces are configured to form any three-dimensional shape.24. An electrowetting-on-dielectric droplet manipulation device (1) comprising: an electrode (8); a first dielectric and hydrophobic layer (15) covering the electrode; a lid (23) disposed over the electrode leaving a space (3o); a second dielectric and hydrophobic layer forming a functional structure (36) over the electrodes, interposed between the first dielectric and hydrophobic layer and the lid.25. The device according to claim 17 or 24 wherein at least one functional structure (36) is a first functional structure (36,) in the shape of first and second semi-circles (38,, 382) with first and second straight edges (40,, 402) positioned alongside opposite electrode edges (41).26. The device according to any one of claims 17 to 25 wherein at least one -0or functional structure (36) is a second functional structure (362) in the shape of a triangle having first and second corners adjacent to an edge (41) of an electrode (8) and a third corner over the centre of the electrode.27. The device according to any one of claims 17 to 26 wherein at least one functional structure (36) is a third functional structure (363) in the shape of a four pointed star having tips of the star close to or at the edges (41) of an electrode (8).