WO2024209179A1

WO2024209179A1 - Control of heating and cooling in 3d bioprinting

Info

Publication number: WO2024209179A1
Application number: PCT/GB2024/050652
Authority: WO
Inventors: Alan COPNER; Jordan COPNER
Original assignee: Copner Biotech Ltd
Priority date: 2023-04-04
Filing date: 2024-03-11
Publication date: 2024-10-10
Also published as: GB202403460D0

Abstract

Disclosed is a 3D printing assembly (10), suitable for bioprinting, the assembly (10) including an enclosure (100) defining an enclosure internal area (101), the assembly further including a bioprinter (200) enclosed within the internal area (101), the bioprinter (200) comprising a bioprinter bed (240), the enclosure (100) comprising plural sides (110), one or more of said sides having at least one temperature regulator element (112) in the respective side (110), wherein the or each temperature regulator element (112) is arranged to introduce heat energy into, and remove heat energy from the internal area (101), and wherein the bioprinter bed (240) has at least one bed temperature regulator element (242) in or on the bioprinter bed (240) further arranged to introduce heat energy into, and remove heat energy from the bioprinter bed (240). The temperature control may be aided by air flow from a fan (131) or the like.

Description

Control of heating and cooling in 3D bioprinting

The invention relates to additive type printing, known also as 3D printing. In particular the invention relates to apparatus and methods for controlling the temperature of 3D printable materials, by regulating the heating or cooling of parts associated with 3D printing before, during and/or immediately after their 3D printing. In particular, the invention relates to so called bioprinting and bioprinters, where the printed/printable materials are biological in nature, for example materials intended for laboratory biological research or the like. Further, not exclusively, the invention relates to temperature control and regulation, providing different temperatures at different locations within an enclosed 3D printing machine. Herein, temperature regulation, and like words are intended to mean physical heating and cooling or maintaining temperature, whereas temperature control and like words are intended to mean the control, management, or command of the temperature regulation.

Good experimental practices dictate that research consumables, like a 3D printed product, should have consistent manufacturing parameters. These parameters include manufacturing temperatures. To a large degree, conventionally, the ambient temperature of a laboratory is relied upon for temperature consistency. However, the inventors have realised that the temperature of materials used in a 3D printed construct may need different temperatures at different stages of their processing, and so the general laboratory temperature, or a similar ambient temperature regulation is neither precise enough nor does it allow different temperatures at different 3D printing process stages.

Materials employed in bioprinting tend to be sensitive to temperature. The usual term for such materials is bioinks. Bioinks have different properties; for example, viscosity and chemical composition, which in turn dictate, for example, the bioink's crosslinking or maturity characteristics after printing. The chemical properties of some of these bioinks can have temperature requirements that differ pre and post print. For example, bio-gels can be warmed to promote flow during printing, but then cooled quickly to promote setting for handling and transfer to a experimental platform. Materials carrying viable cells, bacteria, viruses, and other biological entities usually need to be kept within a defined temperature range at all times and so the inventors have realised that temperature regulation may need to be applied differently at different stages of the printing process, i.e. both heating and cooling, particularly if the 3D printing process inherently generates heat.

Discussed in US11046001B2 is the use of a Peltier element and associated fans at the bed of a 3D printer for regulating heat at the printer bed. This arrangement is useful but does not allow for complete temperature control of the 3D printing process.

Discussed in US11220060B2 is print nozzle temperature control, but again that arrangement does not allow for complete temperature control of the 3D printing process.

US20170056967 discloses a 3D printer suitable for the construction of metallic parts, and which suggests the use of Peltier components at the print head and at the printer bed, (its Fig 1) although no constructional details are given.

CN108995204A discloses, at its Fig 1, temperature control of a side wall and printer bed, again without constructional details.

US20150190966 describes temperature regulation of a printer bed using, as an example a Peltier device, as well as heating a build chamber generally.

JP2019031093A, US20190177676, CN209813097U are furtherdocuments addressing heating and cooling in 3D printing.

In addition to the above matters, an important factor in the use of bioprinters is cleanliness, with the objective of providing as close as possible to a sterile environment for bioprinting. The invention addresses the above aspects. According to one aspect of the invention, there is provided a 3D printing assembly, suitable for bioprinting, the assembly including an enclosure defining an enclosure internal area, the assembly further including a bioprinter enclosed within the internal area, the bioprinter comprising a bioprinter bed, the enclosure comprising plural sides, one or more of said sides having at least one temperature regulator element in the respective side, wherein the or each temperature regulator element is arranged to introduce heat energy into, and remove heat energy from the internal area, and wherein the bioprinter bed has at least one bed temperature regulator element in or on the bioprinter bed further arranged to introduce heat energy into, and remove heat energy from the bioprinter bed, wherein the respective side is formed from two spaced panels, and said temperature regulator element is mounted between said panels in thermal contact with both panels.

Other aspects of the invention are defined by the claims.

The invention can be put into effect in numerous ways, examples of which are shown in the attached drawings, wherein:

Figure 1 shows an isometric view of a 3D bioprinter enclosure utilising the invention;

Figure 2 shows a sectional view in the plane ii-ii shown in Figure 1;

Figure 3 shows another sectional view in the plane iii-iii shown in Figure 1;

Figure 4 shows a schematic of the controller of the bioprinter shown in Figure 1; and

Figure 5 shows an alternative embodiment of a 3D bioprinter and enclosure.

Referring to Figure 1, there is shown a first embodiment 10 of 3D printing assembly including an enclosure 100 for a 3D bioprinter 200 ( shown in Fig 2) operable to manufacture, layer by layer 3 dimensional components described herein as constructs. Principally, the constructs described herein are biological in nature, meaning that they are formed from biocompatible carriers with or without biological entities such as cell, bacteria, viruses, and the like. Such components are used, for example, as supports for biological entities or when printed with the entities as pseudo tissues or organs in laboratory research, for example testing of drug candidates. The enclosure 100 serves to provide a clean, temperature controlled local environment for the printer 200. The enclosure has, in this embodiment, five generally flat sides 110, and another side formed from a pair of flat access doors 120. The construction of the enclosure includes a rectilinear open frame 102 formed from square section metal tubing 104, for example aluminium extrusion sold as 2020 aluminium extrusion (20mm square in section) under different trade names. The frame tubing 104 is joined with suitable corner joints 106 to make the frame skeleton 102. The frame 102 is in-filled with exterior panels 108, in this embodiment, formed of aluminium metallic sheet material affixed to the outside of the frame 102, together with the doors 120 on the front side forming the enclosure 100. Thus a generally closed non-airtight enclosure is formed by the construction above.

The enclosure 100 includes a means for introducing variable positive pressure filtered air into the enclosure 100, in this case an air filtration device 130, comprising a HEPA type filter and fan 131 which provides positive air pressure within the enclosure, in turn aiding the provision a clean environment within the enclosure. The speed of the fan is variable, for example controlled by pulse width modulation (PWM) of its power supply.

In this embodiment the enclosure 100 further includes internal panels 109 which can be sealed to form an airtight enclosure, apart from the two doors 120 each providing an exit 122 for the forced clean air delivered by the fan. Additional filters can be provided at the exits 122 if hazardous materials are used for printing, for example, if viruses or virus-like particles are included in the bioink print material.

The enclosure 100, further includes a liquid pump housing 140 described in more detail below.

Referring additionally to Figure 2, a 3D printer 200 is shown which in use will be enclosed within the enclosure 100 in a generally closed interior space 101. In this Figure the exterior sides 110 are shown in section, more clearly showing the tubing 104 of the frame 102, as well as the flat exterior panels 108 and corresponding interior flat panels 109 on the inside faces of the frame 102. Thereby, double-skinned sides 110 to the enclosure 100 are formed having a cavity 111 which provides a heat-insulated enclosure 100, and improves sound insulation also. For increased thermal efficiency, the edges of the interior panels 109 which abut the frame 102 will be sealed with thermally insulating strips 107. Within the cavity 111 between the exterior 108 and interior 109 panels of at least two opposing sides 110 are two temperature regulators 112. In this case the regulators are solid state heat transfer pumps, for example Peltier devices. In order to effect efficient heat transfer from one panel to the other, heat transfer compound 114 is used to thermally connect the Peltier device with the panels 108 and 109 and thereby provide thermal contact between the inside and outside panels via the temperature regulators 112. Herein, thermal contact has its ordinary meaning, i.e. contact which readily allows heat energy to transfer from one material to the next, including material to material direct contact, or contact with an intermediary material which conducts heat readily, for example a heat conducting adhesive or thermal pad or heat conducting viscous liquid such as grease. The Peltier device 112 will act in use to heat or cool the interior panel 109 and vice versa for the exterior panel 108 depending on the direction of the electrical de current applied to it.

The pump housing 140 houses an air pump 142 which is fed with external air through a filter 144 and provides clean pressurised air to a microfluidic tube 146. The printer 200 further includes a vial holder 210 inside the interior 101. The vial holder is capable of carrying multiple vials 212 or other containers, which contain material M to be printed. The microfluidic tube 146 is inserted into the closed headspace of the vial 212 to allow pressurisation of the material M in use. A further microfluidic tube 245 dipped into the material M provides a fluid path to a print head 220 of the printer 200. In use the tube 245 provides a pressurised feed of material M to the print head 220 for printing.

The printer 200 is mainly conventional, having a printer head drive mechanism 230 which in use drives the printhead 220 in the X and Y directions depicted (where Y is a plane perpendicular into the drawing), and a printer bed 240 which is driven by a bed drive mechanism 250 which in use drives the bed 220 in the Z direction depicted.

The printer bed includes two heat transfer devices 242, conveniently, Peltier devices, in thermal contact with, on their upper sides, a metallic printer bed plate 244, and on their lower sides with finned heat sinks 245. In this embodiment the printer bed plate 244 is a flat 8mm thick aluminium plate which provides good heat conductance and is thick enough to maintain its flatness under different temperatures. Above the bed plate 244 is a removable consumable surface 248 onto which is printed a construct MC formed from the material M. The consumable 248, is conveniently an upturned petri dish or the like, providing a closed air space 252 which provides a reasonably stable and consistent temperature zone at which the 3D printing of the construct MC can take place and inhibits the transfer of heat to or from the enclosed space 101.

The Peltier devices 242 each provide temperature regulation of the bed plate 244 and in turn regulate the temperature of the construct MC. Peltier devices 112 can regulate the temperature of the closed space 101 and therefore regulate the temperature of the material M in the fluidic tubes 146 and, in the vial holder 210 and at the printhead 220.

Fig 3 shows a section of one of the sides 110 in more detail, sectioned through it central plain iii-iii shown in Figure 1. Visible is the frame 102 of one side 110 and its components as well as two Peltier devices 112 mounted diagonally to distribute the heating/cooling effect more evenly across the side 110. In some circumstances it may be required to operate just one of the devices 112, or even operate two devices in opposition (one heating and one cooling the interior space 101 on the same side). To improve efficiency and to negate the circular effect of opposing operation, insulating material 116 is disposed in the cavity 111 formed by the inner and outer panels 109 and 108. In addition a further thermal break 118 can be provided between Peltier devices 112 to reduce thermal 'crosstalk' between them.

Figure 4 shows schematically the controller hardware 300 for the printer 200, which also controls the enclosure 100 temperature(s). The controller 300 includes a conventional 3D printer controller, which accepts files in STL format through a serial communication port 310, and issues motion instructions via an operation port 320 to the printing mechanisms 230 and 250 of the printer along with pump 142 operating instructions and printhead 210 operation instructions. In addition, to control temperature, the controller 300 receives predetermined instructions for target temperatures of the enclosure 101 and of the printer bed 240, for example in the STL instruction file, which may change as printing progresses.

In an alternative embodiment to that described above, the vents 122 (Fig 1) in the doors 120 can be omitted. In that case, the enclosure is configured as a non-airtight enclosure; the two non-sealed doors 120 and gaps between the frame 102 and enclosure wall panels excluding 109 panels provide an exit for the forced clean air delivered by the fan 131 at low speed settings. This arrangement provides for a clean environment for the enclosure internal space, but negates the need for vents 122 in the doors 120. In this way, wipe-clean doors with no discontinuities or protrusions can be provided.

In another embodiment, the door's vents 122 can again be omitted, and the enclosure 100, including the doors can be air-sealed, allowing for a pressure build-up in the enclosed space 101, by virtue of the fan 131 in the air filter 130. When the doors 120 are opened the internal air is released, thereby exhausting air and preventing potentially unclean air entering the internal space 101.

In operation, the actual temperature: at the vial holder is measured by a temperature probe TP1 ; at the printhead by temperature probe TP2; and at the printer bed 240 by probe TP3 (see Figure 2). These actual temperatures are delivered to the controller 300 via communication lines TP1,TP2 and TP3 respectively. The controller includes a PID routine or circuit, whereby the proportion, integral and derivative of any difference in the target and measured temperature values are used to control the current to a respective Peltier device 112/244, in this case using pulse width modulation (PWM) to modify mean de current, and where, heating and cooling can be reversed by reversing the polarity of the current supplied to the respective devices. In this way, temperature regulation ( heating and/or cooling) can be controlled accurately at different zones of the printing process, even such that the Peltier devices 122 can keep the material M at one temperature while it is in the storage 210, transfer 245 and printing 220 zone (zone 1), while the Peltier devices 244 can keep the printed construct MC at a different temperature at the printer bed 240 (zone 2). Since the supply tube 245 is essentially pressurised, this enables the printhead 220 to be simplified, by the use of a piezoelectric nozzle which can be opened and closed very quickly to deliver a precise amount of material to be printed, aided by the fact that the viscosity of the printed material can be gauged accurately, since its temperature is well controlled.

Some examples of the temperature regulation regimes for bioinks are given below:-

Example 1

Collagen Type 1 derived from rat's tails- A printable liquid bioink containing this material is stored in refrigerated conditions below 4 degrees Celsius (°C) in a vial 212, and then transferred to the vial holder 210 prior to use. At zones 1 and 2 the temperature is kept below 4 °C to prevent cross linking of the material. During and/or after printing the temperature is allowed to rise, or is forced to rise by heating at zone 2, to promote cross linking and to solidify the construct during and/or after its printing .

Example 2

Agarose solution- This printable material is pre-warmed, to above 30-50°C or warmed to that temperature range at the vial holder to liquify the material. Zones 1 and 2 are kept at around 30-50°C to prevent the material from cooling and solidifying. During and/or after printing the temperature is allowed to reduce, or is reduced by deliberate cooling at zone 2, to promote solidification of the construct during and/or after its printing.

Example 3

Type A gelatin- This printable material is kept at about 37 °C to prevent gelation. Zones 1 and 2 are prewarmed and kept at about 37 °C to prevent the material from cooling and gelling. During and/or after printing the temperature is allowed to reduce, or is reduced by deliberate cooling at zone 2, to promote gelling of the construct during and/or after its printing.

In the examples above, it should be noted that, since the printing process will generate some heat at zone 2, it is possible that maintaining the same temperature at zones 1 and 2 may require heating at zone 1 and cooling at zone 2 simultaneously. That regime is made possible because the means for heating and cooling at zones 1 and 2 are separate, and can be PID controlled separately. It follows then that a customisable temperature control regime, before during and after printing is possible, using the above mentioned hardware and software thereby allowing a wide range of biomaterials to be printed under controlled temperatures and allowing selectable changes in temperature during and after printing.

The fan 131, provides a mixing of air in the enclosure 101 and thereby promotes a consistent internal temperature throughout zone 1, and can provide heat transfer out of the enclosure 100 via exits 122 , or via gaps around the doors etc when the vents 122 are omitted, when needed. Thereby, the downward direction of air inhibits the print bed 240 from heating the space 101 above it. Additionally, the use of a closed space 250 above the printer bed plate 244 reduces heat transfer between the closed space 101 and the printer bed 240. Increasing the speed of fan 131; optionally with increased/decreased temperature at zone 1 and optionally between the printing of model layers can promote increased drying/setting of the printed layer(s) if so desired for the material(s) being printed.

In another embodiment the speed of the fan 131 can be increased in conjunction with the increased temperature in Zone 1 in order to remove temporary supporting printed artifacts from the 3D printed model; for example the melting away of gelatin supporting artifacts.

In yet another embodiment, the fan is controlled to provide 100% of its speed when the printer power is switched on for about 60-120 seconds to push out any airborne contaminates or bacteria in the internal area of the enclosure at initiation of a printing process. In addition, a door-open sensor (for example an electric switch or internal air pressure sensor) can be used as a signal to power the fan at maximum speed, so that when the door(s) are opened, a positive air pressure is provided in the enclosure, thus mitigating the chance of airborne contamination entering the enclosure with the door(s) open. The boost in fan speed can also aid drying out of any internal surface that has been cleansed, for example with ethanol or another cleaning solvent. Once that maximum pressure routine is complete, the fan is controlled return to its nominal power of around 50% PWM duty cycle.

Embodiments of this invention provide a flexible solution to controlling the bioprinting temperature environment, ensuring that the biomaterial in the vial 212 and its transport route 245 to the printer head 220, being microfluidic tubing with a degree of thermal transfer, are at substantially the same required temperature, and ensuring that, if needed, the printer bed 240 is at an optionally different temperature.

The hardware described above can provide the two mentioned zones each with a consistent temperature of 2-55°C.

The arrangement and construction of the enclosure provides an easily cleanable internal and external shape with generally flat surfaces with no, or few, protrusions. Thereby, the internal contamination load of the internal space 101 can be minimised easily by cleaning.

Figure 5 shows a second embodiment of the invention. A second 3D bioprinting assembly 20 is illustrated, wherein parts which are the same or similar to parts described above have like reference numerals, and have the same or a similar function to that described above. In the embodiment of Figure 5, a more versatile bioink reservoir 310 is provided, which has plural vials, in this case three: 312A, 312B and 312C, which can be selectively fluidically interconnected to a print head 220 via a common microfluidic tube 345, by means of selection valves 311A, 311B and 311C, in turn controllable by the controller 300 (Fig 4). A waste vial 450 is provided, to purge the printing head 220 and supply tube 345, when a different material is selected from the reservoir 310. A purge routine controlled by the controller 300 involves running the air pump 142 and the print head while the print head is positioned over the vial 450 for about 30 seconds until the previously selected bioink material has been purged and the new bioink material is ready to print. Another option for dispensing multiple materials at the print head is to provide a selectively operable valve upstream of each vial 312A,B and C, and non-return check valves in place of valves 311A,B and C, wherein, a single, or multiple air pumps can be used to drive material to the print head, as described above, and the check valves prevent material entering the vials from other vials. In any case, a material in one of the vials may be a cleaning fluid, to clean the print head. There may be more than 3 vials, for example, four, five or six vials may be employed.

The software of the controller 300 may also be configured to enable multiple reservoirs 310 to be employed in a biofabrication process. In this configuration the controller 300 will pause the printing process to allow an operator to exchange the reservoir to one containing different bioinks and/or cleaning materials before continuing the biofabrication process with subsequent printing and/or cleaning steps.

The contents of the reservoir vials is known to the controller as part of its software configuration, such that when the controller attempts to perform a printing step that has a material that is not currently configured for the installed manifold; the controller pauses the biofabrication to enable the operator to excahnge the reservoir with one that contains the required recipe materials; to reconfigure the controller with these new bioinks and/or cleaners before resuming the biofabrication at the next recipe printing step.

Fig 5 further shows an alternative bioprinting mechanism 400 for moving the printhead 220 relative to its bed 240, known as a CoreX-Y mechanism. This mechanism includes two motors 410, one for X movement and one for Y movement and an X-Y motion frame 420, wherein the frame 420 and motors 410 are mounted directly to the enclosure frame 102. In this alternative construction, the frame 420 is an integral part of the enclosure frame 102, adding to its structural strength. This arrangement reduces complexity and makes the whole assembly 20 more rigid. This arrangement also has fewer components around the printing bed, which makes cleaning easier.

One disadvantage of connecting the frame 400 directly to the enclosure frame 102 is that thermal expansion of the parts may affect accuracy of printing. In other words, the Z distance between the printing head and the bed may change due to thermal expansion or contraction. This is mitigated by having a bed height sensor 422. In this case a laser sensor 422 is included to ensure that the Z dimension is measured and, if needed, corrected by the controller 300 as a result of thermal expansion/contraction, or any mechanical wear or inaccuracy. Other dimensional sensors could be used. For example an electrical 'touch' contact could be used to provide a calibrated Z distance measurement.

It will be apparent to the skilled address that the description above is just one way to put the invention claimed into effect and that additions, modifications and omissions are possible without departing from the inventive concept claimed herein. For example: the Peltier devices 112 and 242 shown could be exchanged for other, electrothermal devices, or other heat transfer devices and their quantity could be increased or decreased; aluminium sheet panels 108 and 109 and printer bed 244 are preferred for their good heat conductivity but other metals or non-metals could be used, for example copper, stainless steel, or plastics e.g. plastics loaded with silver ions; the 3D printer mechanism is described in detail, although other mechanisms not necessarily moving with cartesian axes could be employed; specific hardware has been described, for example temperature sensors TP1, TP2 and TP3 are intended to be simple thermistors, however, other temperature sensing could be employed for example other metals based resistance temperature detectors (sold commonly under the names which include the metal's chemical symbol and its resistance at 0°C (for example PT100, PT1000, CU100 etc) or thermocouples or remote IR sensing devices could be used, for example located at the sides 110, and directed toward the relevant features of the printer that require temperature monitoring; and, although STL format file language is commonly used for print files, other file formats could be used, for example a new more data-efficient file format named as GRAPE (TM) which is described in detail in co-pending UK patent application GB2211174.4, the contents of which is hereby incorporated by reference, such a file format providing a smaller size data file compared with STL , and yet a more accurate print, along with the target temperature instructions mentioned above.

Since the invention relates to bioprinters, the quality of the printing environment needs to be consistent, repeatable and controllable, even though the ambient environment may not be consistent and repeatable. Temperature control is an important attribute to control, as mentioned above. Air quality too is improved using a HEPA filter as mentioned above. However, the printing quality may be made even better with additional air treatment apparatus 150, shown in Figure 5. In practice such apparatus may be, for example: additional higher specification air filtration for example an ultra-low particulate air (ULPA) filter, downstream of or instead of the HEPA filter mentioned above; even cleaner air can be provided by passing the air induced into the enclosure by the fan 131 through a UV-c light to reduce bio-burden; an air ioniser can be employed also to attract very small particles in the induced air onto an oppositely charged surface, to improve or further improve air quality; the humidity in the enclosure can be controlled by increasing the water content of the induced air, for example by misting or the introduction of steam, or reduced, for example by passing air over cold plates to remove moisture from that air, all with the aim of achieving a repeatable humidity range during printing. The humidity can be controlled afterthe air quality has been improved, for example by filtering, but before a UV-c light is employed.

Other modifications will be apparent to the skilled addressee.

Claims

1. A 3D printing assembly (10/20), suitable for bioprinting, the assembly (10/20) including an enclosure (100) defining an internal area (101), the assembly further including a bioprinter (200/400) enclosed within the internal area (101), the bioprinter (200/400) comprising a bioprinter bed (240), the enclosure (100) comprising plural sides (110), one or more of said sides having at least one temperature regulator element (112) in the respective side(s) (110), wherein the or each temperature regulator element (112) is arranged to introduce heat energy into, and remove heat energy from the internal area (101), and wherein the bioprinter bed (240) has at least one bed temperature regulator element (242) in or on the bioprinter bed (240) further arranged to introduce heat energy into, and remove heat energy from the bioprinter bed (240), wherein the respective side(s) is/are formed from two spaced panels (108/109), and said temperature regulator element (112) is mounted between said panels in thermal contact with both panels.

2. An assembly as claimed in claim 1 wherein said spaced panels comprise, or each comprise a outer panel (108) exposed externally of the enclosure (100) and an inner panel (109) exposed to the internal area (101), and a cavity (111) therebetween, wherein the or each temperature regulator element (112) is disposed within the cavity (111) and the inner and outer panels (109/108) are in heat conductive communication with each other via the or each temperature regulator element (112).

3. An assembly as claimed in claim 2 wherein said inner and outer panels (109/108) are metallic sheet material, preferably aluminium sheet.

4. An assembly as claimed in any one of the preceding claims wherein said side and/or bed temperature regulator element(s) (112/242) are thermoelectric type devices, for example Peltier devices, allowing selectively for said introduction and removal of heat energy.

5. An assembly as claimed in any one of the preceding claims, wherein the bioprinter (200/400) further includes a bioink storage area (210/310), and a printhead (220) in fluid communication with the storage area for allowing delivery printable material at the print head (220), the storage are and the print head being exposed to the heating and/or cooling of the enclosed area 101.

6. An assembly as claimed in claim 5, including plural temperature sensors (TP1,TP2 and TP3) , for sensing actual temperatures at, at least, the print head (220), the storage area (210), and the bioprinter bed (240).

7. An assembly as claimed in claim 6, including a controller (300) arranged to accept instructions for printing a 3D construct, and instructions indicative of target temperatures at the storage area (210), print head (220) and bioprinter bed (240), the controller being further arranged to accept signals from the sensors (TP1,TP2,TP3).

8. An assembly as claimed in claim 7 wherein the controller (300) is operable to provide power to said temperature regulator elements (112/242) with the objective of reaching the target temperature as measured at said sensors (TP1,TP2,TP3).

9. An assembly as claimed in claim 8 wherein the power to the temperature regulators is controlled by said controller and includes one or more of: a proportional-integral- derivative (PID) routine or circuit; pulse width modulation of electrical power; and a selectively reversable electrical current polarity.

10. An assembly as claimed in any one of the preceding claims 5 to 9, further comprising: a printer pump (142) external to the enclosure (100) for selectively providing positive fluid pressure at the storage area (210/310), and a storage vial (212) or vials (312A,B and C) at the storage area in use providing positive pressure to a headspace within a vial or vials, in turn, for causing fluid in the vial(s) to flow to the print head (220).

11. An assembly as claimed in claim 1 wherein said enclosure includes means for introducing variable positive pressure filtered air into the internal area, said means optionally being a variable speed air-filtering fan (131), optionally controlled by pulse width modulation of the fan's electrical power.

12. An assembly as claimed in claim 11 further including apparatus for treating said air before during or after its introduction into the internal area, said apparatus including one or more of: HEPA filtration, ULPA filtration, UV lighting, an electrical charge at least sufficient to charge particles in the air , and humidity control.

13. An assembly as claimed in any one of the preceding claim, including a frame 102 providing support for the inner and outer panels (108,109), at their edges and defining the cavity, and optionally providing support for at least an X-Y motion frame (420) of the bioprinter (400).

14. An enclosure (100) for enclosing a 3D bioprinter (200/400), the enclosure (100) being formed from sides 110 each side being formed from a sheet metal panel pairs (108) and (109) providing a cavity between the panels, at least one of the sides including a heat regulating element in the cavity disposed between the panel pairs and in thermal contact with the respective pair.

15. A controller (300) for a 3D bioprinter (200), the controller being operable to control the functioning of the 3D bioprinter housed within an internal area of an enclosure (100), to produce a 3D printed construct (MC) in accordance with a 3D printing file, said controller (300) being further operable to control the temperature of at least two temperature regulating devices (122/242), by means of control inputs from plural temperature sensors (TP1,TP2,TP3), at least one sensor sensing the temperature of the print bed (240), at least one temperature sensor sensing the temperature of a print material store (210), and/or at least one temperature sensor sensing the temperature of the bioprinter head (220), and wherein said temperature regulation includes causing: heating of one or more of said at least two devices, cooling of one or more of said devices, or heating of one of the devices at the same time as cooling of another of the devices.

16. A controller as claimed in claim 15, wherein said temperature control operation includes controlling independently temperature regulation devices (112/242) associated with said material store (210), printhead (220) and bioprinter bed (240), by means of one or more of: a proportional-integral-derivative (PID) routine or circuit; pulse width modulation of electrical power; and a selectively reversable electrical current polarity.

17. A controller as claimed in claims 15 or 16, wherein the controller is further arranged to control a means for introducing variable positive pressure treated air into the enclosure, said means optionally comprising a filter air fan, optionally controlled by PWM of the fan's power supply.

18. A controller as claimed in claim 17 wherein said means is controlled in use to provide sufficient flow that air into the internal area such that the air will only exit the internal space, and thereby provide only treated air in the internal space.

19. A controller as claimed in claim 17 or 18, wherein said means is controlled in use to provide sufficient air flow to provide a drying or setting effect of a printed part at the bioprinter bed.

20. A controller as claimed in claims 17, 18 or 19 wherein said means is controlled to provide an increase in air pressure in conjunction with increased temperature at the bioprinter bed, for example to aid removal of temporary supporting printed artifacts from a 3D printed construct, for example the melting away of gelatin supporting artifacts.

21. A controller as claimed in any one of the preceding claims 14 to 20, wherein said printing file provides instructions for both said 3D bioprinter functioning and includes target temperatures for controlling independently said temperature regulation devices (112/242), wherein, optionally said file is in a format known as GRAPE as described in UK pat application GB2211174.4 .

22. A controller a claimed in any one of the preceding claims wherein the controller is further arranged, for example under the control of said printing file, to interrupt the printing process to allow exchange of a reservoir suitable for containing one or more vials of bioink.