CN111065766A

CN111065766A - Hot melt electrostatic spinning

Info

Publication number: CN111065766A
Application number: CN201880053538.5A
Authority: CN
Inventors: S·芬尼根; G·亨迪; M·马奎尔
Original assignee: Avectas Ltd
Current assignee: Avectas Ltd
Priority date: 2017-06-23
Filing date: 2018-06-22
Publication date: 2020-04-24
Also published as: EP3642402B1; WO2018234863A3; ES2908322T3; WO2018234863A2; US20200232121A1; EP3642402A2

Abstract

Systems, devices, and methods for electrospinning are provided. For example, a system includes a current collector including a load sensor coupled thereto, the current collector configured to receive an extruded polymer; and an electrospinning melt head assembly positioned above the current collector and configured to extrude the polymer. The electrospinning melt head assembly and/or the current collector are configured to be movable. The melt head assembly includes an injector assembly and at least one heating element configured to provide heat to the injector assembly. The syringe assembly comprises: a syringe comprising a passageway extending from a proximal end, a passageway configured to receive a polymer, and a nozzle configured to allow the polymer to pass therethrough.

Description

Hot melt electrostatic spinning

Cross Reference to Related Applications

This application claims priority to U.S. provisional application No.62/524,119, filed on 23/6/2017, the entire disclosure of which is expressly incorporated herein by reference.

Technical Field

The subject matter described herein relates to electrospinning techniques that provide reliable fiber output and improved control.

Background

Electrospinning can include a process for producing fibers that utilizes an electrical potential to draw liquid polymer filaments through a gap between a conductive source emitter and a conductive current collector or counter electrode. When a sufficiently high voltage is applied to the droplet, the body of liquid may become charged, the electrostatic repulsion forces may counteract the surface tension forces, and the droplet may be stretched from the emitter. At the critical point, the droplet will eject a stream of liquid as it extends from the emitter to the counter electrode. The geometry of the extended droplet ejected therefrom is known as the taylor cone. If the molecular cohesion of the liquid is sufficiently high, cracking can be avoided and a charged liquid jet can be formed. During the process from the emitter to the current collector, the liquid flow will dry out. As the liquid stream dries and/or cools, the mode of the electrical current may change from an ohmic mode to a convective mode as charge migrates to the surface of the forming fiber. When flowing towards the current collector, the liquid flow may be moved by a "stirring" process to create small bends in the fibers, which may cause the fibers to thin and elongate until they are deposited onto the current collector. The attenuation and elongation caused by the agitation process can result in the formation of uniform fibers of nanometer-scale diameters.

Much of this research has been directed to the use of solution electrospinning, and less research has been done on melt electrospinning because the process most commonly produces fibers greater than 1 μm_{Melt body}) And non-conductive polymer melts (typically less than 10-10S/m conductivity), the absence of solvent can be substantialReduction of surface charge density (σ)_q) Thus reducing bending instability. When the temperature of the charged jet is below the glass transition temperature (T) of the polymer_g) The rapid solidification of the melt stream further inhibits agitation; since a greater disturbing force is required to overcome the surface tension. The initial region of the charged melt stream is typically of considerable volume and motion from the centerline is reduced. The suppression of bending instability greatly reduces the degree of stretching encountered by the melt electrospinning jet prior to solidification. Melt electrospinning is typically characterized by larger fiber diameters than in solution due to the lack of thinning caused by solvent evaporation.

Through careful process design, optimization and control, sub-micron fibers can be obtained in melt electrospinning. Similar to melt extrusion systems, this can be achieved by controlling the extensional viscosity and solidification of the filaments in a hot environment. However, since melt electrospinning is a more complex problem, in addition to the heat transfer effects of conservation of momentum and mass, viscoelasticity, and in some cases crystallization in flight, the electric field and charge transfer effects must be considered. By other material modifications prior to processing, polymer melts can be used to produce fiber diameters approaching true nanometer scale: rather than delivering the polymer into solution, adding additives to increase the conductivity of the polymer melt is another strategy to increase the charge density by stretching on the melt jet, thereby causing a greater degree of stretching of the jet during flight.

Disclosure of Invention

The subject matter of the present application can include an electrospinning melt assembly that can monitor and control the temperature of the polymer, reduce thermal fluctuations in the polymer to achieve uniform melting of the polymer, measure the deposited material using load cells on a current collector during experimental runs will allow a user to monitor the extrusion rate, and use a corrected sinusoidal offset profile during extrusion that can provide a smoother linear offset profile, and thus can better deposit fibrous structures. In addition, the subject matter of the present application can include active measurement and feedback of the electric field between the emitter and collector of the electrospun melt assembly by current or charge sensors that can control the applied voltage, allowing the electric field density to be maintained.

In one aspect, a system includes a current collector including a load cell coupled thereto, the current collector configured to receive an extruded polymer; and an electrospinning melt head assembly positioned above the current collector and configured to extrude the polymer. The electrospinning melt head assembly and current collector are configured to move relative to each other (e.g., the current collector may move while the melt head assembly is stationary, the melt head assembly may move while the current collector is stationary, or both the current collector and the melt head assembly may move). The melt head assembly includes an injector assembly and at least one heating element configured to provide heat to the injector assembly. The syringe assembly comprises: a syringe comprising a passageway extending from a proximal end configured to receive a polymer, and a nozzle configured to allow passage of the polymer therethrough.

Any one possible combination may include one or more of the following features. For example, the syringe assembly may include a plunger sized and shaped to be slidably received within the channel such that distal movement of the plunger causes extrusion of the polymer. The system may further include a plunger drive system configured to provide a mechanical force to actuate the plunger. The system may include an imaging system configured to monitor extrusion of the polymer; and a probe configured to measure an electric field intensity between the nozzle and the current collector. The system may further include a control and processing system configured to receive signals from the plunger drive system, imaging system, load cell, and the probe, and to control the position of the electrospinning melt head assembly, the force applied to the plunger, the voltage of the current collector, and the extrusion rate of the polymer.

The system may further include a plunger drive system configured to provide pressure inside the syringe. The system may further include a support assembly holding the electrospinning melt head assembly.

The extrusion rate can be controlled to follow a sinusoidal profile. In some embodiments, the extrusion rate is between 0.1 g/hr and 10 g/hr. For example, the extrusion rate can be 0.1 g/hr, 0.2 g/hr, 0.3 g/hr, 0.4 g/hr, 0.5 g/hr, 0.6 g/hr, 0.7 g/hr, 0.8 g/hr, 0.9 g/hr, 1.0 g/hr, 2.0 g/hr, 3.0 g/hr, 4.0 g/hr, 5.0 g/hr, 6.0 g/hr, 7.0 g/hr, 8.0 g/hr, 9.0 g/hr, or 10.0 g/hr. The voltage of the current collector may be between 0 and 20kV, 1kV, 2kV, 5kV, 10kV, 15kV, 20kV, 25kV, 30kV or 40 kV. A voltage source may be included that provides a maximum current of 0.01mA, 0.1mA, 0.18mA, 0.2mA, 0.3mA, 0.6mA, 1.0mA, 10mA, or 10mA to the current collector. The system may include a drive system, which may include a plunger or may operate without a plunger, such as with a gas. For example, the system may include a drive system including a pump configured to provide pressure inside the syringe via a gas.

The melt head assembly and/or current collector may be configured to move in three or more directions, such as x, y, or z. In some embodiments, the melt head assembly and/or current collector may be movable in directions beyond x, y, z. For example, the melt head assembly and/or current collector may be moved in any specified coordinate system, such as polar, spherical, or cylindrical coordinates, among others. Further, in some embodiments, the melt head assembly and/or current collector may move in 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and/or more directions. In some embodiments, the x-direction and the y-direction are separated by 90 degrees, while the z-direction is separated by 90 degrees from a plane formed in the x-direction and the y-direction. In some embodiments, the current collector moves such that the melt head assembly moves relative to the current collector. In some embodiments, the current collector may comprise a cylindrical shape and rotate about the central channel. In some embodiments, the current collector may comprise a flat plate.

In another aspect, an electrospinning system includes a current collector, an electrospinning melt head assembly, a plunger drive system, an imaging system, and a probe. The current collector includes a load cell coupled thereto. The current collector is configured to receive an extruded polymer. The electrospun melt head assembly is positioned above the current collector and is configured to extrude a polymer. The electrospinning melt head assembly is configured to move in X, Y and Z directions. The melt head assembly includes an injector assembly and at least one heating element configured to provide heat to the injector assembly. The syringe assembly includes a syringe, a plunger, and a nozzle. The syringe includes a passageway extending from the proximal end. The channel is configured to receive the polymer. The plunger is sized and shaped to be slidably received within the channel such that distal movement of the plunger causes polymer extrusion. The nozzle is configured to allow the polymer to pass therethrough. The plunger drive system is configured to provide a mechanical force to actuate the plunger. The imaging system is configured to monitor extrusion of a polymer. The probe is configured to measure an electric field strength between the nozzle and the current collector.

Any one possible combination may include one or more of the following features. For example, a control and processing system may be included and may be configured to receive signals from a plunger drive system, an imaging system, a load cell, and a probe, as well as to control the position of the electrospinning melt head assembly, the force applied to the plunger, the voltage of the current collector, and the polymer extrusion rate.

A support assembly may be included to hold the electrospinning melt head assembly.

In another aspect, an electrospinning melt head assembly includes an injector assembly including a nozzle, a plunger including at least one sealing element disposed on an outer surface thereof, a first channel extending from a first opening in a proximal end of the injector assembly, the channel sized and shaped to slidably receive the plunger such that the at least one sealing element on the plunger forms a seal with a wall defining the first channel, a distal second opening fluidly connected to the first channel, the second opening sized and shaped to releasably receive a portion of the nozzle therein; and at least one heating element configured to provide heat to the injector assembly.

Any one possible combination may include one or more of the following features. For example, a heater assembly may be included that retains the at least one heating element, the heater assembly including a second passage extending from a proximal end thereof, the second passage being sized and shaped to receive at least a portion of the syringe assembly. The at least one heating element may surround the second channel. The heating element may be disposed within a lower half of the heater assembly. An insulating sleeve may be included. The insulating sleeve may include a third channel configured to receive the syringe assembly and the at least one heating element.

In another aspect, energy can be applied to the heating element to generate heat for transfer to the polymer. The temperature associated with the polymer is measured. The polymer was melted in the syringe. A voltage is applied to the current collector to create an electric field across a gap between the current collector and a nozzle releasably coupled to the injector. The nozzle passes over a portion of the current collector at least once. A force is applied to a proximal end of a plunger slidably disposed within the syringe to urge the plunger toward the nozzle, thereby forcing a portion of the polymer out of the nozzle and into an electric field, thereby creating a polymer stream extending from the nozzle. The polymer stream cools and forms fibers from the nozzle to the current collector.

Any one possible combination may include one or more of the following features. The size of the gap can be adjusted each time the nozzle passes a given point on the collector. The nozzle may be moved based on an offset profile to create a small bend in the polymer stream. The offset profile may comprise a corrected sinusoidal profile. A load cell may be used to determine the rate at which polymer is extruded from the nozzle. The imaging system may be used in conjunction with machine vision software to determine the rate at which polymer is extruded from the nozzle. Air pressure will create a force on the proximal end of the plunger. The air pressure can be reduced sufficiently to pull the plunger out of the nozzle, thereby stopping or reducing the flow of polymer from the nozzle. The electric field strength can be measured. The voltage of the current collector may be adjusted according to the measured electric field strength. The size of the gap between the nozzle and the current collector may be adjusted based on the measured strength of the electric field.

In another aspect, a system includes a current collector including a load cell coupled thereto, the current collector configured to receive an extruded polymer; an electrospun melt head assembly disposed over said current collector and configured to extrude said polymer, wherein said electrospun melt head assembly is configured to move in X, Y and a Z direction, said melt head assembly comprising an injector assembly and at least one heating element, said at least one heating element configured to provide heat to said injector assembly, said injector assembly comprising: a syringe comprising a passageway extending from a proximal end, the passageway configured to receive a polymer, a nozzle configured to allow passage of the polymer therethrough; a plunger drive system configured to provide pressure inside the syringe; an imaging system configured to monitor extrusion of the polymer; and a probe configured to measure an electric field strength between the nozzle and a current collector.

Any one possible combination may include one or more of the following features. The system may further include a control and processing system configured to receive signals from the plunger drive system, imaging system, load cell and probe, and to control the position of the electrospinning melt head assembly, the pressure supplied to the injector, the voltage of the current collector and the extrusion rate of the polymer. The system may further comprise a support assembly for holding the electrospinning melt head assembly.

In another aspect, an electrospinning melt head assembly includes an injector assembly including a nozzle, a first channel extending from a first opening at a proximal end of the injector assembly, a second opening at a distal end, the second opening fluidly coupled with the first channel, the second opening sized and shaped to releasably receive a portion of the nozzle therein; at least one heating element configured to provide heat to the injector assembly.

Any one possible combination may include one or more of the following features. For example, the assembly may further include a heater assembly for holding the at least one heating element, the heater assembly including a second channel extending from a proximal end thereof, the second channel being sized and shaped to receive at least a portion of the syringe assembly. The at least one heating element may surround the second channel. The heating element may be disposed within a lower half of the heater assembly. The assembly may further include an insulating sleeve including a third channel configured to receive the syringe assembly and the at least one heating element.

Drawings

FIG. 1 is an exploded view of an exemplary embodiment of an electrospinning melt head assembly;

FIG. 2 is an enlarged view of an injector assembly of the electrospinning melt head assembly of FIG. 1;

FIG. 3 is a cross-sectional view of a nozzle of the syringe assembly of FIG. 2;

FIG. 4 is an enlarged view of a heater assembly of the electrospinning melt assembly shown in FIG. 1;

FIG. 5 is a schematic perspective view of another embodiment of a heater assembly;

FIG. 6 is a side cross-sectional view of the heater assembly of FIG. 5;

FIG. 7 is a schematic perspective view of the injector assembly of FIG. 2 and the heater assembly of FIG. 5;

FIG. 8 is a bottom schematic view of the injector assembly of FIG. 2 positioned within the heater assembly of FIG. 5;

FIG. 9 is an exploded view of the support assembly;

FIG. 10 is an enlarged schematic view of the upper cover and heater assembly support plate of the support assembly of FIG. 9;

FIG. 11 is a cross-sectional view of the electrospinning melt head assembly of FIG. 1 within the support assembly of FIG. 9;

FIG. 12 is a schematic diagram of an embodiment of an electrospinning system;

FIG. 13 is a schematic diagram of signal communication between the control and processing system and various other components of the electrospinning system of FIG. 12;

FIG. 14a is an offset profile;

FIG. 14b is an additional embodiment of an offset profile;

fig. 15 is a perspective view of a cap of the syringe assembly of fig. 2;

FIG. 16 is a bottom view of the cover of FIG. 15;

FIG. 17 is a perspective view of a syringe cap of the electrospinning melt head assembly of FIG. 1;

fig. 18 is a top view of the syringe cap of fig. 17;

fig. 19 is a side view of the syringe cap of fig. 17;

FIGS. 20A-F illustrate some aspects of exemplary embodiments of the present subject matter; and

fig. 21 is a table detailing certain technical specifications of embodiments of an electrospinning system that may be similar to the electrospinning system of fig. 12.

Detailed Description

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems, devices, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. Features illustrated or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of the subject matter of this application. Moreover, in the present disclosure, identically named components of an embodiment typically have similar features, and thus each feature of each identically named component need not be fully set forth in a particular embodiment.

Electrospinning can include a process for producing polymer fibers that utilizes an electrical potential to draw liquid polymer filaments through a gap between a conductive source emitter and a conductive current collector or counter electrode. This process can be used to produce scaffolds on which cells and tissues can be seeded and grown. One way in which the process can be improved is by reducing thermal fluctuations in the polymer to achieve uniform melting and thus uniform extrusion of the polymer. Uniform extrusion can improve control of scaffold properties, such as porosity. By better controlling the properties of the scaffold, a more repeatable scaffold configuration can be achieved and the properties of the scaffold can be optimized for tissue growth. In addition, the uniform geometry may provide a perfect match between cell size and scaffold, the potential for mechanical cues from the uniform geometry, such as enhanced nerve guidance, predictable (by model) mechanical properties of the scaffold in dynamic settings, such as the aorta, and fiber diameter and pore size in individual scaffolds. The temperature of the melt head can be monitored and tracked over time to determine the stability of the system. Tracking can be performed using thermal sensors, such as PT100 Resistance Temperature Devices (RTDs) and analog I/O devices, to measure and control the process. ("Pt" is the symbol for platinum, "100" represents the resistance at 0 ℃ in ohms). In addition, tracking can be performed using (1) data logging with a computer and thermocouples and/or RTDs and (2) an error term e in a proportional-integral-derivative (PID) controller. The error term e may be the difference between the set point and the measured temperature and may be integrated over the manufacturing time of the stent (minutes to hours). Stability can be achieved by (1) an auto-tuning function on the PID controller, but can also be determined by (2) a tuning/stability method such as ziegler-nicols tuning. Stability ensures that the emitter reaches and maintains the desired temperature with minimal overshoot.

Another way in which the electrospinning process could be improved is to measure the deposited material using a load cell on the current collector during the experimental run, allowing the user to monitor the extrusion rate. For example, a single load cell capable of measuring micro newton forces as a function of time f (t) may be employed. The load cell may be placed between the movable platform and the counter electrode. The load cell may have sufficient dynamic range to bear the weight of the platform and still be able to measure small forces. The signal from the load cell may be low pass filtered to derive a signal that varies slowly with increasing force as the mass of deposited material increases. Such signals may also be used to modulate material deposition rates. Any rapid change in f (t) may indicate an erroneous or uneven deposition and may indicate an alarm condition for the software. In addition, the use of a rectified sinusoidal offset profile during extrusion may provide a smoother linear offset, thereby providing a better deposited fiber structure. As another example, active measurement and feedback of the electric field between the emitter and collector from a current or charge sensor may allow control of the applied voltage, allowing the electric field density to be maintained.

In some embodiments, feedback may be monitored and controlled to increase the separation distance per pass, and may be combined with any control of the electric field to ensure consistency of the process through each pass.

Fig. 1 shows an exploded view of an exemplary embodiment of an electrospinning melt head assembly 100. Melt head assembly 100 may include an injector assembly 110, a heater assembly 140, a high temperature insulating sleeve 170, and an injector cap 190. The syringe assembly 110 may function to hold and controllably deposit the polymer onto the substrate. Syringe assembly 110 may be received within heater assembly 140, which may function to heat the polymer to a desired temperature, and heater assembly 140 may be inserted into insulating sleeve 170. A melt head cover may be positioned over the proximal ends of injector assembly 110 and heater assembly 140 to provide a layer of insulation while allowing access to injector assembly 110 and heater assembly 140. The specific components of the electrospinning melt head assembly 100 will be discussed in more detail below.

Fig. 2 shows an enlarged view of the syringe assembly 110 of fig. 1. The syringe assembly 110 may include a syringe 112, a plunger 114, a cap 116, and a nozzle 118. As shown in fig. 1-2, the syringe 112 may have a substantially cylindrical geometry and may include a first opening 120a on the proximal end 112a, a second opening (not shown) on the distal end 112b, and a passageway 120 extending therebetween along a central axis a 2. A channel 120 extending from the proximal end 112a to the distal end 112b may receive a polymer to be heated and extruded, deposited, or spun onto a substrate. The opening 120a at the proximal end may receive the plunger 114. the plunger 114 may have at least one or more sealing members 113, such as O-rings, that may form a seal with the walls of the passageway 120 of the syringe 112. In some embodiments, the plunger may have two sealing elements 113. In some embodiments, the plunger may be made of stainless steel. The plunger may be translated proximally and distally within the channel 120 of the syringe 112 to control the extrusion of the polymer. Indeed, the position of the plunger 114 may be controlled in a variety of ways. For example, the position of the plunger 114 may be changed by applying positive air pressure to the proximal end 114a of the plunger 114. Alternatively, a shaft may be connected to the opening 115 in the proximal end 114a of the plunger, and a force may be applied to the plunger 114 via the shaft. Using air pressure to adjust the position of the plunger 114 may be beneficial because it may simplify construction and reduce cost. Air or some other suitable air pressure may be applied directly to the molten polymer to cause it to be extruded through the nozzle. The method of operation will be discussed in more detail below.

The cap 116 may function to couple the nozzle 118 with the syringe 112 and provide access to the passageway of the syringe 112 through the distal end 112 b. In the illustrated embodiment, the cap 116 has a generally cylindrical body and includes a cylindrical mating feature 122 extending in a proximal direction. The mating feature 122 may allow the cap 116 to be releasably coupled to the syringe 112 via a second opening on the distal end 112b of the syringe 112. The cap 116 may be coupled to the syringe 112 in a variety of ways. For example, the mating feature 122 has threads that can mate with threads in the second opening of the syringe 112. Alternatively, the mating feature 122 and the second opening may be coupled via, for example, a friction fit. In some embodiments, the mating feature 122 may include a seal 124 disposed on an outer surface thereof. The mating feature 122 may be received within the second opening of the syringe 112, and the seal 124 may form a seal between the mating feature 122 and the channel 120 of the syringe 112. In some embodiments, the seal may comprise an O-ring that may be made of perfluoroelastomer FFKM. Further, the mating feature 122 may have a curved surface 117, which may be formed with the distal end 114b of the plunger.

As shown in fig. 1-2, the injector 112 and the cap 116 may include

apertures

126a, 126b and

apertures

126c, 126d, all of which may be threaded, and

temperature measurement channels

128a, 128 b. The

apertures

126a, 126b may allow the syringe 112 to be coupled to the cap 116. Fig. 15-16 show enlarged views of the cover 116. As shown in fig. 2, 15 and 16, the

apertures

126b, 126d may be larger than the

apertures

126a, 126 c. This helps to ensure that the cap 116 and syringe 112 are properly aligned during assembly. The hole 126a may be aligned with the hole 126b, the hole 126c may be aligned with the hole 126d, and the syringe 112 may be coupled to the cover 116 by a coupling element, such as a screw or bolt, that may extend through the

holes

126a, 126b, 126c, 126 d. The

temperature measurement channels

128a, 128b may receive temperature measurement sensors, such as thermocouples, PT100 RTDs, etc., that may extend through the injector 112 and into the cap 116 to monitor the temperature of the cap 116 as close as possible to the nozzle 118. Although not shown, the syringe 112 and cap 116 may include a plurality of temperature measurement channels that may receive temperature measurement sensors. The inclusion of multiple channels may allow multiple temperatures to be measured at different locations along the length of the injector 112 and the cover 116. In an exemplary embodiment, the syringe 112 and the cap 116 may be made of stainless steel. Stainless steel can provide good corrosion resistance, thermal conductivity, and workability. However, the syringe 112 and cap 116 may be made of any corrosion resistant material, such as titanium, nickel, or any other material suitable for the purpose. In some embodiments, the cap 116 may be integrated with the syringe 112.

As shown in fig. 3, the nozzle 118 may include a central passage 130 extending through a proximal mating portion 131 and a distal extrusion portion 132. The central passage 130 may have a first portion 135 and a second portion 137, wherein the first portion 135 has a first diameter and the second portion 137 has a second diameter. The first portion 135 may extend from the inlet 130a to the proximal end 118a of the proximal mating portion and the second portion 137 may lead to the outlet 130b at the distal end 118b of the distal extrusion 132. The distal injection portion 132 may include an inner inwardly tapered surface 132a, which may form a transition region that may couple the first portion 135 of the channel 130 to the second portion 137 of the channel 130. The inner inwardly tapered surface 132a may result in the diameter of the outlet 130b of the nozzle 118 being smaller than the diameter of the inlet 130a of the nozzle 118. In some embodiments, the coating of conductive material may cover a portion of the extruded portion 132 of the nozzle 118. When connected to a suitable high voltage source, the coating may act as a high voltage electrode.

In some embodiments, a high voltage source applying a voltage of 0 to 20kV may be included. In some embodiments, the voltage source may provide a voltage of 1kV, 2kV, 5kV, 10kV, 15kV, 20kV, 25kV, 30kV, 40kV, or higher. The power supply may provide a voltage resolution of, for example, 10V. In some embodiments, the voltage source may provide a maximum current of 0.18 mA. In some embodiments, the voltage source can provide a maximum current of 0.01mA, 0.1mA, 0.2mA, 0.3mA, 0.6mA, 1.0mA, 10mA, 100mA, or more.

In the illustrated embodiment, the proximal mating portion 131 of the nozzle 118 may include threads that may mate with threads in the opening 119 (shown in fig. 16) in the cap 116. In an exemplary embodiment, the nozzle 118 may be made of a material having a coefficient of thermal expansion greater than that of the cap 116. For example, if the cap 116 is made of stainless steel, the nozzle 118 may be made of brass. Thus, when the melt head assembly 100 is heated, the nozzle 118 may expand more than the cap 116, which helps form a seal between the threads on the mating portion 131 of the nozzle and the threads in the opening in the cap 116.

To provide heat to the polymer within the injector 112, the injector assembly 110 may be inserted into the heater assembly 140. Fig. 4 shows an enlarged view of the heater assembly 140 shown in fig. 1. The heater assembly 140 may include a heating element 154, a heating member 142 or body, which may be in the form of, for example, a cylindrical sleeve, and a heater cover 144 and mounting flange 146. The heating member 142, the heater cap 144, and the mounting flange 146 may each have a substantially cylindrical geometry. The mounting flange 146 may include a sleeve coupling aperture 146a, a heater aperture 146b, a support coupling aperture 146c, and a center aperture 146 d. The sleeve coupling apertures 146a may be aligned with the coupling apertures 143a on the proximal end 142a of the heating member 142 and may allow the mounting flange 146 to be coupled to the heating member 142 using coupling elements such as screws or bolts. The support connection apertures 146c may be used to allow the heater assembly 140 to be coupled to a support frame, which will be discussed in more detail below.

As shown in fig. 4, the heating member 142 may have a generally cylindrical geometry and may include a first opening 148a on the proximal end 142a, a second opening (not shown) on the distal end 142b, and a channel 148 extending therebetween. The heating member 142 may include a connection hole 143a on the proximal end 142a and a heater hole 143 b. As described above, the coupling holes 143a on the heating member 142 may be aligned with the coupling holes 146a on the mounting flange 146, and may allow the heating member 142 and the mounting flange 146 to be coupled using coupling elements such as screws or bolts. The heater apertures 143b may extend through the length of the heating member 142 and may be aligned with the heater apertures 146b of the mounting flange 146 on the proximal end 142a of the heating member 142 and with the heater apertures 145b of the cover 144 on the distal end 142b of the heating member 142.

The heater cover 144 may include a heater hole 145b and a connection hole 145 a. Heater cap 144 may have a recessed region 150 extending distally from an opening 150a in proximal end 144a, and may also include an aperture 152 extending through distal end 144b of cap 144. Central bore 146d, channel 148, recessed area 150, and bore 152 may share central axis a3 and may be aligned such that syringe assembly 110 may be received within heater assembly 140. Recessed area 150 of cap 144 may receive and seat a distal portion of syringe assembly 110, and aperture 152 may allow nozzle 118 to extend through distal end 144b of heater cap 144.

A heating element 154, such as a cartridge heater, may be used to provide heat to the injector assembly 112. In some embodiments, the heating element 154 may be a 200W cartridge heater. In other embodiments, the heating element may generate more than 200W of heat, or less than 200W of heat. Heating element 154 may be inserted through

heater apertures

146b and 143b and may extend into heater aperture 145b in heater cover 144. The heating element 154 may heat the mounting flange 146, the heating member 142, and the heater cap 144, which in turn may heat the polymer within the syringe assembly 110 and the syringe 112. In some embodiments, heating element 154 may heat heater assembly 140 to a temperature of about 250 ℃.

The heating member 142, mounting flange 146, and cover 144 may be made of any material suitable for the purpose. However, in an exemplary embodiment, the heating member 142, the mounting flange 146, and the cover 144 may be made of aluminum. Aluminum has a relatively high thermal conductivity, which may result in a more uniform temperature distribution because heat from the heating element 154 may be well conducted through each portion of the heater assembly 140.

The injector assembly 110 and the heater assembly 140 may be insulated using, for example, an insulating sleeve 170 to minimize heat loss and improve temperature control. Referring back to fig. 1, insulation sleeve 170 may include a passage 172, which passage 172 may extend between an opening 172a of a proximal end 170a of insulation sleeve 170 and an opening (not shown) of a distal end 170b of insulation sleeve 170. The injector assembly 110 and the heater assembly 140 may be inserted into the passage 172 of the insulating sleeve 170. The insulating sleeve 170 may be made of any insulating material capable of withstanding the highest temperatures of the heating element 154. In some embodiments, the insulating sleeve may be made of calcium silicate. The insulating sleeve 170 and the heating element 154 may form a concentrated heating zone. The concentrated heating zone concentrates heat in the volume of the injector where the polymer is loaded during operation.

To provide insulation at the proximal end of the syringe 112, a syringe cap 190 may be positioned on the proximal end 112a of the syringe and/or mounting flange 146. Syringe cap 190 has a generally cylindrical geometry and may include an array of apertures 192 that may extend from a proximal end 190a of syringe cap 190 to a distal end 190b of syringe cap 190. In some embodiments, a portion of the cap 190 may extend to the syringe 112In the channel 120 such that it forms a seal with the walls defining the channel 120. In some embodiments, syringe cap 190 can be made of, for example, Duro

280(agk), Polyetheretherketone (PEEK) or

(IGUS INC, East Providence R.I. 02914). Fig. 17-19 show various views of the syringe cap 190. The bore 192 may provide access to the injector assembly 110 and/or the heater assembly 140. For example, the at least one bore 196 may provide access to the temperature measurement channel 128a such that the temperature sensor 129 may be inserted into the

temperature measurement channel

128a, 128 b. In some embodiments, the temperature sensor 129 may be a 4mm PT100 temperature sensor or a type K thermocouple. In some embodiments, the syringe cap 190 may include

attachment holes

195a, 195c, which may be aligned with the

holes

126a, 126c of the syringe 112 and may allow the syringe cap 190 to be attached to the syringe 112 using attachment elements such as screws or bolts. The syringe cap 190 may also include mounting holes 197, which will be discussed further below. A hose connector may be connected to the gas inlet 193 so that gas pressure may be applied to the plunger to force the polymer liquid out of the nozzle. Alternatively, the shaft may extend through the inlet 193 and may connect to the opening 115 in the proximal end 114a of the plunger. The shaft may then apply mechanical force to the plunger to move it proximally and/or distally within the channel 120 of the syringe 112. In some embodiments, the gas may be applied directly to the molten polymer. In some embodiments, a solenoid valve may be utilized to control gas pressure, including applying positive and negative pressures to the plunger. Such a method may provide improved control over the extrusion process.

In some embodiments, the heater assembly may have an integral configuration, rather than having multiple assemblies such as described with respect to heater assembly 140. The heater assembly may also embed a heating element. Fig. 5-6 illustrate an example of an embodiment of a heater assembly 240 having a unitary configuration and which may have one or more embedded heating elements 254. The temperature sensor may also be embedded in an integrated configuration. Fig. 5 shows a perspective schematic view of heater assembly 240, while fig. 6 shows a side cross-sectional view of heater assembly 240. Heater assembly 240 may have a body 242, which body 242 may have a generally cylindrical geometry, and which may include a central passage 248, which central passage 248 may extend from an opening 248a in the proximal end 240a of heater assembly 240 to the distal end 240b of heater assembly 240. The proximal end 240a of the heater assembly 240 may include a flange 246, which may extend radially outward. The flange 246 may have a support coupling aperture 246c, the support coupling aperture 246c functioning similarly to the support coupling aperture 146 c. The distal end 240b of the heater assembly may have an aperture 252 that may receive a nozzle, such as the nozzle 118 of the injector assembly 110. In the illustrated embodiment, the central passage 248 and the bore 252 may share a central axis a 4.

Heater assembly 240 may also include a port 260 having a radial passage 262, and radial passage 262 may extend from an end 260a of port 260 to central passage 248. The port 260 may allow wires to enter and exit the passage 248. For example, a wire from temperature sensor 129 capable of monitoring the temperature of an injector assembly (e.g., injector assembly 110) may pass through passage 262 of port 260.

In the illustrated embodiment, the heating element 254 may be embedded in a centrally heated region 256 of the body 242 of the heater assembly 240 rather than inserting the heating element into a hole of the heater assembly as described with respect to the heater assembly 140. In some embodiments, the heating zone 256 may be limited to the lower or distal half of the heater assembly 240. The heating element 254 may be one or more resistive heaters that may surround or wrap around the channel 248 in the body 242 of the heater assembly 240. Heating element 254 may receive power from a power source via cable 257, which cable 257 may extend out of body 242 of heater assembly 240. Using a heater assembly configuration that includes a heating element surrounding the channel 248 may provide more uniform heat transfer to the injector assembly 110, which may result in a more uniform temperature distribution of the polymer. Such a configuration may improve the accuracy of the control system that may be used to monitor and maintain the temperature of the polymer within the syringe assembly 110 and/or syringe 112. By creating a more uniform temperature distribution, the temperature measurement may be less sensitive to the precise location of the temperature sensor 129, thereby increasing the accuracy and precision of the temperature measurement. In some embodiments, the channel 262 of the port 260 does not extend into the channel 248. In this case, the channel 262 may be used to pass a cable that may be coupled to the heating element 254 or temperature sensor within the wall of the heater assembly. For example, cable 257 may extend from heating element 254 to channel 262 and out of heater assembly 240, rather than out of body 242 of heater assembly 240.

Fig. 7 and 8 illustrate how syringe assembly 110 is received within heater assembly 240. Fig. 7 shows syringe assembly 110 aligned with opening 248a in proximal end 240a of the heater assembly. Fig. 8 shows syringe assembly 110 positioned within passageway 248 of the heater assembly.

Regardless of which heater assembly is used, the melt head assembly 100 may be supported within a support assembly. As shown in fig. 9, the support assembly 300 may include upper and

lower covers

302, 304, side covers 305, 306, upper and lower support frames 308, 309, and a heater assembly support plate 310.

The lower cover 304 may be generally in the shape of a square or rectangular plate. In some embodiments, the lower cover 304 may be made of Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), and/or other electrically insulating and heat resistant materials. The lower cap 304 may have a recessed area 312 extending distally from an opening 312a in the proximal surface 304a, and may further include an aperture 352 extending from the recessed area 312 to the distal surface 304b of the cap 304. The lower cap 304 may also have a connection hole 314a that may extend distally from the proximal surface 304a of the lower cap 304. The recessed region 312 may be sized and shaped to receive the distal portion of the insulative sleeve 170. Aperture 352 may be generally aligned with aperture 252 of heater assembly 240 such that it may receive nozzle 118 of injector assembly 110.

As shown in fig. 9, the support assembly 300 may include upper and lower support frames 308, 309 or structural ribs. In some embodiments, the upper and lower support frames 308, 309 may be made of aluminum. The support frames 308, 309 may be generally square or rectangular in shape and may have a perimeter dimension approximately equal to the lower cover 304. The support frames 308, 309 may have

channels

316, 318 extending from the proximal surfaces 308a, 309a to the distal surfaces 308b, 309b of the frames. In the illustrated embodiment, the

channels

316, 318 have a generally square shape. However, the

channels

316, 318 may have any geometry suitable for receiving and retaining the melt head assembly 100. In addition to the

channels

316, 318 for receiving the melt head assembly 100, the support frames 308, 309 may have a first set of

attachment holes

320a, 321a, a second set of

attachment holes

320b, 321b, and a third set of

attachment holes

320c, 321 c.

In the illustrated embodiment, the side covers 305, 306 include attachment holes 319 b. The connection holes 319b may be aligned with the connection holes 320b, 321b of the support frames 308, 309 to allow the side covers 305, 306 to be connected to the support frames 308, 309 using, for example, screws, bolts, or pins. As shown in fig. 9, the support plate 306 may also include larger connecting holes 319c and passages 322. In some embodiments, the channel 322 may be used to feed power cables from an external power source to the cartridge heater 154 or the heating element 254. These cables can be managed through the use of wireways and labels. The cable may further comprise an entrance filter to improve the electromagnetic compatibility (EMC) characteristics of the system and/or to prevent electrical leakage. The

holes

320c, 321c may be aligned with the holes 319c on the side cover 306 and they may allow the melt head assembly 100 and the support assembly 300 to be connected to a mounting assembly (not shown) using a connecting element, such as a screw, bolt, or other spacing mechanism, such as a spacing post, rod, or adapter plate, among others. In some embodiments, the side covers 305, 306 may be made of aluminum and may be white powder coated. Although the side cover 305 is shown as a three-fold aluminum sheet, each side of the side cover 305 may be a single sheet similar to the side cover 306.

Fig. 10 shows an enlarged view of the upper cover 302 and the heater assembly support plate 310. In some embodiments, the upper cover 302 may be made of aluminum and may be a white powder coating, and the heater support plate 310 may be made of Polyetheretherketone (PEEK). The heater assembly support plate 310 may also be generally square or rectangular in shape and may have a perimeter dimension approximately equal to the lower cover 304. The support plate 310 may have a recessed area 324 extending distally from an opening 324a in the proximal surface 310a, and may further include an aperture 326 extending from the recessed area 324 to the distal surface 310b of the support plate 310. The support plate 310 may also include a connection hole 328a and first and second sets of

counter-sunk connection holes

330a, 332 a. Additionally, the recessed area may include a syringe cap 190 mounting hole 325. The cap mounting holes 325 may align with mounting holes 197 on the syringe cap, which may allow connection elements, such as screws, bolts, or other connection elements suitable for the purpose of the description, to connect the syringe cap 190 to the heater assembly support plate 310.

The upper cover 302 may be generally square or rectangular in shape and may include a connection aperture 334a that may be aligned with the connection aperture 328a in the support plate 310 and a central aperture 336 that may be aligned with the opening 324a in the support plate 310.

The support assembly 300 may be assembled by connecting the various components using connecting elements, such as screws, bolts, and/or pins, among others. The distal end 170b of the insulative sleeve 170 may be positioned in the recessed area 312 of the lower cap 304.

The distal surface 318a of the lower support frame 309 may be positioned above the proximal surface 304a of the lower cover 304 such that the connection hole 320a is aligned with the connection hole 314 a. The connection members may be inserted into the

connection holes

314a, 320a to connect the lower support frame 309 to the lower cover 304.

Heater assembly 240 may be inserted into channel 172 of insulating sleeve 170 such that bore 252 of heater assembly 240 is aligned with bore 352 of lower cap 304. Although not shown, insulating sleeve 170 may have a radial hole to allow port 260 of heater assembly 240 to pass therethrough. The electrospinning melt head assembly 100 and the support assembly 300 may be assembled as follows.

Syringe assembly 110 may be inserted into heater assembly 240. A polymer useful for electrostatic spinning may be inserted into the channel 120 of the injector 112. The polymer may be in the form of beads.

The upper support frame 308 may be connected to the side covers 305, 306 using connecting elements that may extend through some of the connecting holes 319b in the side covers 305, 306 and into the connecting holes 320b on the upper support frame.

The upper support frame 308 having the side covers 305, 306 releasably attached thereto may be positioned on the insulating sleeve 170 such that the remaining portions of the attachment holes 319b are aligned with the attachment holes 321b on the lower support frame 309.

The larger attachment holes 319c on the side cover 306 may be releasably attached to the third set of

attachment holes

320c, 321c on the upper support frame 308 and the lower support frame 309.

The heater support plate 310 may be positioned over the insulating sleeve 170, the heater assembly 240, and the injector assembly 110. Heater support plate 310 can be releasably attached to proximal end 240a of heater assembly 240 by attachment elements that can be inserted into countersunk attachment holes 330a on heater assembly 240 and attachment holes 246c on proximal end 240a of heater assembly 240. The heater support plate 310 may also be coupled to the upper support frame 308 by coupling elements that may be inserted into the countersunk coupling holes 332a and the coupling holes 320a on the upper support 308.

The distal end 190b of the syringe cap 190 may be placed in the recessed area 324 of the heater support plate 310. Although not shown, the syringe cap 190 may have a sealing element extending around its perimeter that may form a seal with the recessed region 324.

The upper cover 302 may be coupled to the heater support plate 310 by coupling members that are insertable into the coupling holes 334a in the upper cover 302 and the coupling holes 328a in the support plate 310.

If a multi-component heater assembly is used, such as heater assembly 140, it may be assembled as described above and incorporated into melt head assembly 100 in the same manner as heater assembly 240. Fig. 11 illustrates a cross-sectional view of the electrospinning melt head assembly 100 shown in fig. 1 within the support assembly 300 shown in fig. 9. As shown in fig. 11, a portion 190c of the cap 190 may extend into the channel 120 of the syringe 112 such that it forms a seal with the walls defining the channel 120.

Fig. 12 shows a schematic of an embodiment of an electrospinning system 400. The electrospinning system 400 may include an electrospinning melt head assembly 100 including a support assembly 300, a current collector assembly 402, an imaging system 404, a plunger drive system 406, a probe 408, and a control and processing system 410. As described above, melt head assembly 100 may be assembled and coupled to support assembly 300 and may be mounted on a mounting assembly (not shown) that allows melt head assembly to move along X, Y and the Z-axis.

As described above, the plunger 114 of the syringe assembly 110 may be actuated by applying air pressure to the proximal surface 114a or by using a rigid mechanical connector such as a rod. The plunger drive system 406 may deliver air or another mechanical force to the plunger to produce a proximal or distal displacement to expel the polymer liquid or draw it back into the syringe 112. In some embodiments, the plunger drive system 406 may include a pump. The plunger drive system 406 may send and receive signals to and from the control and processing system 410 to control the position of the plunger 114 to control the flow of polymer from the nozzle 118. In some embodiments, the plunger 114 may be omitted, such that the applied gas pressure directly expels or draws the polymer liquid back into the syringe 112. The gas supplied into the injector 112 is not limited to air, but may include any inert gas such as nitrogen or argon. In some embodiments, omitting plunger 114 may be advantageous in some embodiments because in embodiments utilizing a plunger, molten polymer may be extruded through a nozzle even if no driving force is applied. Due to the airtight fit between the piston and the walls of the melting chamber, any expanding air in the system during the heating phase may drive the molten polymer through the nozzle as it may not be released.

As the polymer exits nozzle 118, it may be deposited onto current collector 412 of current collector assembly 402. The current collector assembly 402 may include a current collector 412, a base 414, and one or more load cells 416, which may be used to determine the amount of polymer that has been deposited onto the current collector 412. By measuring the amount of polymer that has been deposited onto the current collector, the rate of polymer extrusion from nozzle 118 can be determined. In some embodiments, the nozzle 118 may be grounded and high voltage power may be supplied to the current collector 412 such that an electric field is generated between the current collector 412 and the nozzle 118. In some embodiments, the current collector 412 may have a conductive coating that may allow it to function as an electrode. In other embodiments, the current collector 412 may be electrically conductive.

In addition to or as an alternative to using load cell 416 to measure the amount of polymer deposited on current collector 412, imaging system 404 may be used in conjunction with machine vision software to determine the rate of extrusion of the polymer and track the amount of polymer extruded. The imaging system 404 may have a field of view (FOV) that includes the nozzle 118 and the current collector 412.

As the polymer wire is deposited into the region of the current collector 412, sometimes referred to as the boundary, and the height of the polymer support is increased, the electric field generated between the nozzle 118 and the current collector 412 may be altered and/or attenuated due to the insulating properties of the polymer. Probe 408 may measure the electric field between nozzle 118 and current collector 412. The probe 408 may be, for example, a field grinder or an Electric Field Meter (EFM). Additionally, or alternatively, the probe 408 may measure the charge of the current collector 412 and/or the polymer on the current collector. Information about the electric field between the nozzle 118 and the current collector 412 can be used to adjust the power delivered to the current collector 412 or the voltage of the current collector 412, allowing the electric field density to be maintained. The information about the electric field may also be used to adjust the position of the electrospinning melt head assembly 100 in the Z-direction with each pass, thereby changing the electric field. In some embodiments, the current collector 412 may have a dotted and/or spiked surface, which may allow for a more consistent electric field density during polymer deposition. In some embodiments, the dots and/or pegs may extend about 1mm, 2mm, or less than 10mm from the surface of the current collector. The dots and/or pins may be arranged in an array, which may have varying pitches. Regions of the current collector 412 may also have dots and/or spikes that may be arranged in different densities. In other words, certain areas of the current collector 412 may have more closely packed dots and/or spikes than in other areas of the current collector 412.

The electrospinning process occurs over a short separation distance between the current collector 412 and the nozzle 118. In a similar manner to the electric field, as the height of the stent increases with each pass, the spacing between the current collector 412 and the nozzle 118 may also be increased to maintain a consistent deposition distance between the nozzle 118 and the previously placed polymer fibers.

The position of the nozzle 118 may be monitored and feedback may be used to increase the separation distance per pass. The nozzle 118 may be monitored and controlled, and may be combined with any control of the electric field, to ensure consistency of the process area with each pass of the nozzle 118 at a given point of the current collector 412.

Fig. 13 illustrates a signal communication diagram between the control and processing system 410 and various other components of the electrospinning system 400. As shown in fig. 13, the control and processing system 410 may include an image processing module 422, an electric field module 424, a load module 426, a plunger module 428, a heater module 430, and a current collector module 432.

The heater module 430 may send and receive signals to and from the temperature sensor 129 and the heating element 254. In operation, a desired polymer temperature may be selected by the control and processing system 410. The selected temperature may correspond to an initial power that may be provided to the heating element from the power source. The temperature of the nozzle 118 may be measured in the

temperature measurement channels

128a, 128b of the injector assembly 110 using a temperature sensor 129. The temperature sensor 129 may send a temperature signal to the heater module 430, and the heater module 430 may analyze the signal, calculate the temperature, determine the appropriate action of the heating element 254, and send a corresponding heating signal to the heater element 254. System behavior can be coordinated in developed hardware and software to issue signals to adjust multiple inputs (e.g., temperature, stage position, material deposition rate, etc.) and to compute the inputs to produce outputs (e.g., heater coil power, plunger offset, electric field potential, etc.). In some embodiments, a Resistance Temperature Detector (RTD), such as a PT100RTD, may be used to measure the temperature of the nozzle 118. In this case, the heater module 430 may measure the resistance across the temperature sensor 129 and correlate the resistance to a temperature value. In other embodiments, a thermocouple, such as a type K thermocouple, may be used to measure the temperature of the nozzle 118. The melting temperature of the polymer may be determined empirically prior to loading the polymer into the injector 112. For example, phase transition experiments can be performed by heating and melting a polymer and measuring the temperature of the polymer throughout the heating and melting process. In some embodiments, the heating signal may be from a power source of the heater module. The heater module 430 may include a Proportional Integral Derivative (PID) controller and may utilize PID control with an automatic regulation function to control the power delivered to the heating element 254. The input may be a temperature signal from the temperature sensor 129 and the output may be a heating signal. The auto-tuning function can determine the thermal response of the system over time and can calculate system parameters to properly drive the system. As described above, the temperature sensor 129 may be an RTD, a thermocouple, or both. If more than one temperature sensor 129 is used, one sensor may be used as a reference for the PID controller and another sensor may be used to monitor the melting temperature of the polymer. The use of a type K thermocouple is more dynamic than a PT100 temperature sensor. This may reduce or prevent overshoot of the polymer, as the heater may reach the desired set point more quickly, and thus may approach steady state when sufficient conduction occurs. In contrast to some embodiments, this may include a stepwise heating process. In addition, the use of separate monitoring and control temperature probes allows for fine temperature adjustment of the melt set point, thereby avoiding natural losses. In some embodiments, the PID controller reference temperature may be built into the heating head so that it cannot be removed, which reduces the chance of the system overheating to an irreversible damage point.

Once the temperature sensor outputs a signal corresponding to the desired temperature of the polymer, the melt head assembly 100 may be heated for a period of time to ensure that it reaches thermal equilibrium. Due to the thermal conductivity of the loaded polymer, the polymer that is not in direct contact with the syringe 112 will melt. The time required to melt all of the polymer will depend on the mass of the polymer and its thermal conductivity.

The PID temperature may further include dual relay control, temperature lock and internal alarm/latch on the heater power line to improve user safety and/or performance of the device.

When the system reaches thermal equilibrium, the polymer may be extruded through nozzle 118. High voltage power may be provided to the current collector 412 from the current collector module 432. The collector module 432 may also monitor the voltage at the collector 412 and the position of the nozzle 118 in the X, Y and Z directions. The plunger module 428 may also send a drive signal to the plunger drive system 406. Plunger drive system 406 may receive the drive signal and may provide air pressure to the space between proximal end 114a of plunger 114 and distal end 190b of syringe cap 190 to drive plunger 114 distally within channel 120 of syringe 112 to cause the polymer liquid to flow from nozzle 118. Alternatively, if the plunger is driven by a rod, the plunger drive system 406 may apply a force to the rod to move the plunger. If air pressure directly drives the molten polymer without a plunger, the plunger drive system 406 may receive the drive signal and may provide air pressure to the space between the proximal end of the molten polymer and the distal end 190b of the syringe cap 190, causing the polymer liquid to flow out of the nozzle. The rate of this natural extrusion may depend on the viscosity of the molten polymer. The low viscosity molten polymer extrudes very quickly, while the high viscosity polymer extrudes very slowly.

At the critical point, a stream of polymer liquid may be ejected from the droplets as they extend from nozzle 118 to the current collector. The stream may dry during travel from the nozzle 118 to the current collector 412. When the stream dries or cools, the mode of the current can change from ohmic to convective as the charge migrates to the surface where the fibers are formed. When moving toward current collector 412, current collector module 432 may send a motion signal to a mounting assembly (not shown) that keeps melt head assembly 100 moving melt head assembly 100 along the X-Y plane, creating a small bend in the optical fiber that can cause the optical fiber to thin and elongate until the optical fiber is deposited onto the current collector. In some embodiments, the mounting assembly holds the current collector 412 to move the current collector in the X-Y plane to cause small bending wrinkles in the optical fibers, which may cause the optical fibers to subsequently stretch until they are deposited onto the current collector 412. The thinning and elongation caused by the X-Y motion can result in the formation of uniform fibers of nanometer diameter. The X-Y motion of melt head assembly 100 and/or current collector 412 may be achieved by an XYZ drive system, which may be achieved using various actuation mechanisms, such as a ball-and-screw (ball-and-screw) drive system or a linear positioner. When using a linear positioner, linear interpolation can be facilitated to maintain a constant speed during curve travel, without acceleration or deceleration during turns, so a grid with circular features can be placed. In addition, a constant line speed may prevent crimped melt electrospun fibers.

In some embodiments, the G-code can be used to create a polymer scaffold at a certain porosity and density. In other embodiments, position table logic may be used to command movement of the melt head assembly 100. The offset curve of the linear motion phase is important to create thin, straight fibers. Extrusion and deposition of straight fibers may depend on the velocity profile of the linear motion stage. If the speed is not properly matched to the extrusion rate (electrospinning rate), i.e., the extrusion rate is too fast or too slow, the deposited fibers may be crimped rather than straight. The offset curve 500 can be seen in fig. 14 a. The offset plot 500 shows that each stroke has a first portion 502 showing linear acceleration, a second portion 504 showing constant velocity, and a third portion 506 showing constant linear deceleration at the end of the stroke. The nature of the excursion curve 500 is abrupt, given the short-term and rapid nature of the excursion. Rather than using the offset curve 500 shown in FIG. 14a, as shown in FIG. 14b, an offset curve 600 using a corrected sinusoidal curve 602 may provide a smoother linear offset and therefore better deposited fiber.

Returning to fig. 13, the imaging system 404 may monitor the rate and volume of polymer extrusion from the nozzle 118 as polymer fibers are deposited onto the current collector 412. The imaging system 404 may pass the imaging signals to an image processing module 422. Image processing module 422 may communicate the rate signals to collector module 432 and plunger module 428. The collector module 432 and the plunger module 428 may receive the rate signal and may transmit the signal to the collector 412 and the plunger drive system 406 to adjust the voltage of the collector 412 and the pressure applied to the plunger 114, respectively. By adjusting the voltage at the current collector 412, the electric field density can be maintained.

Load cell 416 may measure pressure based on the weight of the polymer fibers on current collector 412 and may transmit a corresponding signal to load module 426. Load module 426 may receive the signal, determine how much polymer is on current collector 412, and the rate of extrusion, and may transmit a corresponding load signal to current collector module 432 and plunger module 428. For example, the mass of polymer on current collector 412 may be determined by load cell 416 and load module 426. The known density, molar mass, and/or molecular weight of the polymer, as well as the mass measured on the current collector 412, can be used to determine the volume of the polymer. The rate of polymer extrusion can be derived by determining the change in mass/volume of polymer on current collector 412 and dividing by the time elapsed between measurements. The load signal may be an analog signal and may be converted to a digital signal by load module 426. Collector module 432 and plunger module 428 may transmit signals to nozzle 118 and plunger drive system 406 to adjust the voltage and extrusion rate of nozzle 118, respectively.

The probe 408 may measure the electric field strength between the nozzle 118 and the current collector 412 and may transmit an electric field signal to the electric field module 424. The electric field signal may correspond to the strength of the electric field between the nozzle 118 and the current collector 412, and/or the charge of the current collector 412. In some embodiments, the electric field module 424 may include a microampere or other charge/current detector. Thus, the current collector 412 may deliver a charge signal to the electric field module 424. The charge signal may correspond to the charge of the current collector 412. The electric field module 424 may receive field and charge signals from the probes 408 and the current collectors 412, respectively, and may communicate the signals to the current collector module 432. Collector module 432 can receive the signal and can adjust the voltage of collector 412 or adjust the position of melt head assembly 100 in the Z-axis, thereby adjusting the gap distance between nozzle 118 and collector 412. Current collector module 432 may also transmit signals to plunger module 428 and plunger module 428 may transmit signals to plunger drive system 406 to adjust the rate of extrusion.

The rate of polymer extrusion can also be reduced or stopped at any time during the extrusion process. For example, the polymer extrusion rate is determined to be too high, or if extrusion is complete, the plunger module 428 may transmit a signal to the plunger drive system 406 indicating that the plunger 114 should be retracted. The plunger drive system 406 may create a vacuum pressure behind the plunger 114 to draw it proximally into the passageway 120 of the syringe 112 to draw the polymer liquid from the nozzle 118. In other words, the air pressure applied to the proximal end of plunger 114 may be reduced sufficiently to draw the plunger proximally within channel 120 to stop or reduce the flow of polymer from nozzle 118.

In the embodiment of the electrospinning system 400 described above, the nozzle 118 is grounded while a voltage is applied to the current collector 412. However, in some embodiments, a voltage may be applied to the nozzle 118, and the current collector 412 may be grounded or provide another voltage. This configuration may create an electric field between nozzle 118 and current collector 412 that may facilitate polymer extrusion.

In some embodiments, the electrical, fluidic, and temperature subsystems may be integrated into a single housing. The subsystem may further comprise a safety circuit for improving user safety. Further, the electrical, fluid and temperature subsystems may be controlled by, for example, a Programmable Logic Controller (PLC) based on closed loop control of the Ethernet IP protocol. The use of a PLC may reduce manufacturing assembly time and allow a user to store operating parameters in memory for repeatable deployment. Further, by using a PLC, the system can be set up to be operational when all operating parameters are within acceptable ranges. The PLC may also include safety functions to prevent overheating of the heater, control the high pressure module, and monitor system pressure. In addition, the PLC of the system may have a Human Machine Interface (HMI) to provide independent operation without requiring the PC to interact with the operator regarding operating parameters such as pressure, temperature, speed, and cycle times, providing feedback, errors, current programs, temperature, speed, pressure values, and voltage values for the operator.

Fig. 20A-F illustrate some aspects of exemplary embodiments of the present subject matter. Melt electrospinning can be considered as an alternative polymer processing technique that enables the fabrication of three-dimensional scaffolds. Some embodiments may be solvent-free and allow the use of less soluble polymers. Some embodiments may enable advances in the field of tissue engineering where solvent retention and toxicity may be a concern. Some embodiments of the present subject matter may include a melt electrospinning apparatus capable of melting polymers having melting points up to 250 degrees celsius. Some embodiments may enable Melt Electrospinning Writing (MEW) by using an x-y stage as the collection stage. Fig. 20A shows the interaction between the process and operating parameters of the MEW, including polymer, current collector, voltage, software, distance, heating element, translation speed and flow rate, etc. Fig. 20B shows a schematic of the MEW instrument. Fig. 20C shows a table of polymers, molecular weights, and melting temperatures. The polymer comprises Polycaprolactone (PCL), Polydioxanone (PDS), polylactic-co-glycolic acid (PLGA), Thermoplastic Polyurethane (TPU), and Polystyrene (PS). Fig. 20D-F illustrate output scaffolds constructed using an exemplary MEW system, illustrating morphology, resolution, and versatility of different structures and materials.

Fig. 21 shows a table detailing certain specifications of an embodiment of an electrospinning system that may be similar to electrospinning system 400.

In some embodiments, the control system conditions and buffers the signal to a robust industrial solution (0-10 volts). Data acquisition hardware is used and its values are provided to a software module that drives the output through an analog output (e.g., 12-bit pulse width modulation). Alarms, boundaries, maximum, minimum and mean values may be calculated.

In some embodiments, the melt head assembly may move in directions other than x, y, z. For example, the melt head assembly may be moved in any specified coordinate system, such as polar, spherical, or cylindrical coordinates, among others. Further, the melt head assembly may be movable in 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and/or more directions. In some embodiments, the x-direction and the y-direction are 90 degrees apart from a plane formed in the x-direction and the y-direction, and the z-direction is 90 degrees apart. In some embodiments, the current collector moves such that the melt head assembly moves relative to the current collector. In some embodiments, the current collector may also be cylindrical and rotate about its own central axis

Other embodiments are within the scope and spirit of the disclosed subject matter.

The techniques described herein may be implemented using one or more modules. As used herein, the term "module" refers to computing software, firmware, hardware, and/or various combinations thereof. At the very least, however, a module should not be construed as software that is not implemented on hardware, firmware, or recorded on a non-transitory processor-readable recordable storage medium (i.e., the module itself is not software). Indeed, a "module" is to be interpreted as always comprising at least some physical, non-transitory hardware, such as a processor or a part of a computer. Two different modules may share the same physical hardware (e.g., two different modules may use the same processor and network interface). The modules described herein may be combined, integrated, separated, and/or duplicated to support various applications. In addition, functions described herein as being performed at a particular module may be performed at one or more other modules and/or by one or more other devices, either alternatively or in addition to functions performed at the particular module. Further, a module may be implemented across multiple devices and/or other components, local or remote to each other. Additionally, a module may be moved from one device and added to another device, and/or may be included in both devices.

One or more aspects or features of the subject matter described herein may be implemented in digital electronic circuitry, integrated circuitry, a specially designed Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA) computer hardware, firmware, software, and/or combinations thereof. These various aspects or functions may include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. A programmable or computing system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

These computer programs, which may also be referred to as programs, software applications, components, or code, include machine instructions for a programmable processor, and may be implemented in a high-level procedural, object-oriented programming, functional programming, logical programming, and/or assembly/machine language. The term "machine-readable medium" as used herein refers to any computer program product, apparatus and/or device, such as magnetic discs, optical disks, memory and Programmable Logic Devices (PLDs), used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal used to provide machine instructions and/or data to a programmable processor. A machine-readable medium may store such machine instructions non-transitory, such as a non-transitory solid state memory or a magnetic hard drive or any equivalent storage medium. A machine-readable medium may alternatively or additionally store such machine instructions in a transitory manner, such as a processor cache or other random access memory associated with one or more physical processor cores.

To provide for interaction with a user, one or more aspects or features of the subject matter described herein may be implemented on a computer having a display device, e.g., a Cathode Ray Tube (CRT) or Liquid Crystal Display (LCD) or Light Emitting Diode (LED) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other types of devices may also be used to provide for interaction with a user. For example, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including but not limited to acoustic, speech, or tactile input. Other possible input devices include, but are not limited to, a touch screen or other touch sensitive device, such as a single or multi-point resistive or capacitive touchpad, voice recognition hardware and software, optical scanners, optical pointers, digital image capture devices and related device interpretation software, and the like.

In the description above and in the claims, phrases such as "at least one" or "one or more" may be presented, followed by a combined list of elements or features. The term "and/or" may also be present in a list of two or more elements or features. The phrase is intended to mean any element or feature listed individually or in combination with any other recited element or feature, unless the context in which the phrase is used implies or otherwise clearly contradicts. For example, the phrase "at least one of a and beta; "" one or more of a and beta; "" A and/or B "means" A alone, B alone, or A and B together, respectively. Similar explanations apply to lists containing three or more items. For example, at least one of the phrases "a, B, and C; one or more of "" "A, B, and C; "A, B and/or C" means "A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together", respectively ". Additionally, the use of the term "based on" is intended to mean "based at least in part on" in the above as well as in the claims, thereby also allowing for unrecited features or elements.

The subject matter described herein may be embodied in systems, apparatuses, methods, and/or articles of manufacture depending on the desired configuration. The embodiments set forth in the foregoing description do not represent all embodiments consistent with the subject matter described herein. Rather, they are merely some embodiments consistent with aspects related to the described subject matter. Although some variations have been described in detail above, other modifications or additions are possible. In particular, other features and/or variations may be provided in addition to those set forth herein. For example, the above-described embodiments may be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several other features disclosed above. In addition, the logic flows depicted in the figures and/or described herein do not necessarily require the particular order shown, or sequential order, to achieve desirable results. Other implementations may be within the scope of the following claims.

Claims

1. A system, comprising:

a current collector comprising a load cell attached thereto, the current collector configured to receive an extruded polymer; and

an electrospun melt head assembly disposed over the current collector and configured for extruding a polymer, wherein the electrospun melt head assembly and/or current collector is configured to be movable, the melt head assembly comprising an injector assembly and at least one heating element configured for supplying heat to the injector assembly, the injector assembly comprising:

a syringe comprising a channel extending from a proximal end thereof, the channel configured to receive the polymer, an

A nozzle configured to allow the polymer to pass therethrough.

2. The system of claim 1, wherein the syringe assembly further comprises:

a plunger sized and shaped to be slidably received within the channel such that distal movement of the plunger causes extrusion of the polymer;

wherein the system further comprises a plunger drive system configured to provide a mechanical force to actuate the plunger.

3. The system of claim 2, further comprising:

an imaging system configured to monitor extrusion of the polymer; and

a probe configured to measure an electric field strength between the nozzle and a current collector.

4. The system of claim 3, further comprising a control and processing system configured to receive signals from the plunger drive system, imaging system, load cell and probe, and to control the position of the electrospinning melt head assembly, the force applied to the plunger, the voltage of the current collector and the extrusion rate of the polymer.

5. The system of claim 4, wherein the extrusion rate is controlled to follow a rectified sinusoidal profile.

6. The system of claim 4, wherein the extrusion rate is between 0.1 g/hr and 10 g/hr.

7. The system of claim 6, wherein the extrusion rate is 0.1 g/hr, 0.2 g/hr, 0.3 g/hr, 0.4 g/hr, 0.5 g/hr, 0.6 g/hr, 0.7 g/hr, 0.8 g/hr, 0.9 g/hr, 1.0 g/hr, 2.0 g/hr, 3.0 g/hr, 4.0 g/hr, 5.0 g/hr, 6.0 g/hr, 7.0 g/hr, 8.0 g/hr, 9.0 g/hr, or 10.0 g/hr.

8. The system of claim 4, wherein the voltage of the current collector is between 0 and 20kV, 1kV, 2kV, 5kV, 10kV, 15kV, 20kV, 25kV, 30kV, or 40 kV.

9. The system of claim 4, further comprising a voltage source that provides a maximum current of 0.01mA, 0.1mA, 0.18mA, 0.2mA, 0.3mA, 0.6mA, 1.0mA, 10mA, or 100mA to the current collector.

10. The system of claim 1, further comprising:

a drive system comprising a pump configured to provide pressure inside the injector via a gas.

11. The system of claim 1, further comprising a support assembly for holding the electrospinning melt head assembly or the current collector.

12. An electrospinning melt head assembly, comprising:

a syringe assembly, comprising, in combination,

a nozzle is arranged at the bottom of the spray nozzle,

a plunger including at least one sealing element disposed on an exterior surface thereof,

a first channel extending along a first opening at the proximal end of the syringe assembly, the channel being sized and shaped to slidably receive the plunger with at least one sealing element on the plunger forming a seal with a wall defining the first channel,

a distal second opening in fluid connection with the first channel, the second opening being sized and shaped to releasably receive a portion of the nozzle;

at least one heating element configured to provide heat to the injector assembly.

13. The assembly of claim 12, further comprising a heater assembly holding the at least one heating element, the heater assembly having a second channel extending from a proximal end thereof, the second channel sized and shaped to receive at least a portion of the syringe assembly.

14. The assembly of claim 13, wherein the at least one heating element surrounds the second channel.

15. The assembly of claim 13, wherein the heating element is disposed in a lower half of the heater assembly.

16. The assembly of claim 13, further comprising an insulating sleeve having a third channel configured to receive the syringe assembly and the at least one heating element.

17. A method, comprising:

applying energy to the heating element to generate heat to transfer to the polymer and melt the polymer within the syringe;

measuring a temperature associated with the polymer;

applying a voltage to a current collector to generate an electric field across a gap between the current collector and a nozzle, wherein the nozzle is releasably coupled to the injector;

moving the nozzle and/or current collector at least once through a portion of the current collector; and

applying a force to a proximal end of a plunger, wherein the plunger is slidably disposed within the syringe, moving the plunger toward the nozzle, thereby displacing a portion of the polymer out of the nozzle and into an electric field, causing it to generate a polymer stream extending from the nozzle, wherein the polymer stream cools and forms fibers during travel from the nozzle to the current collector.

18. The method of claim 17, further comprising adjusting the size of the gap for each pass through the nozzle at a given point on the current collector.

19. The method of claim 17, further comprising moving the nozzle and/or current collector based on an offset profile to create a small bend in the polymer stream.

20. The method of claim 19, wherein the offset profile comprises a corrected sinusoidal profile.

21. The method of claim 17, further comprising determining a polymer extrusion rate from the nozzle using a load cell.

22. The method of claim 17, further comprising determining a polymer extrusion rate from the nozzle using an imaging system in conjunction with machine vision software.

23. The method of claim 17, wherein air pressure generates the force at a proximal end of the plunger.

24. The method of claim 23, further comprising reducing the gas pressure sufficiently to pull the plunger away from the nozzle to stop or reduce the flow of polymer from the nozzle.

25. The method of claim 17, further comprising measuring the strength of the electric field.

26. The method of claim 25, further comprising adjusting a voltage of the current collector based on the measured intensity of the electric field.

27. The method of claim 25, further comprising adjusting a size of a gap between the nozzle and a current collector based on the measured intensity of the electric field.

28. A system, comprising:

a current collector comprising a load cell attached thereto, the current collector configured to receive an extruded polymer;

an electrospinning melt head assembly disposed above the current collector and configured for extruding the polymer, wherein the electrospinning melt head assembly and/or the current collector are configured to be movable in X, Y and the Z direction, the melt head assembly comprising an injector assembly and at least one heating element, the at least one heating element configured to provide heat to the injector assembly, the injector assembly comprising:

a syringe comprising a channel extending along a proximal end thereof, the channel configured to receive the polymer,

a nozzle configured to allow the polymer to pass therethrough;

a drive system configured to provide pressure to an interior of the syringe;

an imaging system configured to monitor extrusion of the polymer; and

29. The system of claim 28, further comprising a control and processing system configured to receive signals from the drive system, imaging system, load cell, and the probe, and to control the position of the electrospinning melt head assembly, the pressure applied to the injector, the voltage of the current collector, and the extrusion rate of the polymer.

30. The system of claim 28, further comprising a support assembly for holding the electrospinning melt head assembly or the current collector.

31. An electrospinning melt head assembly, comprising:

a syringe assembly comprising

A nozzle is arranged at the bottom of the spray nozzle,

a first channel extending along a first opening at a proximal end of the syringe assembly,

a second opening at a distal end, the second opening in fluid connection with the first channel, the second opening sized and shaped to releasably receive a portion of the nozzle therein;

32. The assembly of claim 31, further comprising a heater assembly holding the at least one heating element, the heater assembly including a second channel extending along a proximal end thereof, the second channel being sized and shaped to receive the at least a portion of the syringe assembly.

33. The assembly of claim 32, wherein the at least one heating element surrounds the second channel.

34. The assembly of claim 32, wherein the heating element is disposed in a lower half of the heater assembly.

35. The assembly of claim 32, further comprising an insulating sleeve comprising a third channel configured to receive the syringe assembly and the at least one heating element.

36. The devices, systems, articles, and techniques described or illustrated herein.