An Open-Source 3D Gel Printer as Co-Creation Platform in Soft Matter Manufacturing

Abstract

Polymer gels, which are one of soft matter, are in an intermediate state between solid and liquid and has both solid and liquid properties. In particular, the polymer gels including water as the solvent are called hydrogels. Animals and plants containing water can be considered as hydrogels. By adjusting a ratio of the solid to liquid components of polymer gels and a state of polymer chains, the hydrogels can cover almost all the elastic modulus of the biological tissues [1]. These unique properties of polymer gels have received explosive attention over the past 30 years.

However, the softness of polymer gels has made it difficult to fabricate complex shapes because the polymer gels are mainly formed by mold techniques. In the molding procedure, the mold design (the draft angle) and the material properties (the interaction between parts and molds) should be considered. The procedure has hindered the creating applications of soft matter and the development of soft matter manufacturing.

Additive manufacturing (AM) is a relatively new research area, similar to research of polymer gels, that can produce geometrically complex customized products with less material and less waste. AM has the ability to create parts directly from digital models in one step. The democratisation of AM technologies, brought about by the low cost and open-source 3D printers, is likely to enable more advanced types of co-creation. For these reasons, AM is one of the technologies to solve global issues, for instance as listed in the United Nations Sustainable Development Goals (UN SDG) [2]. It is expected that new value will be created in society by the fusion of AM technologies and research of polymer gels.

In this study, we report an open-source 3D gel printing system as the co-creation platform of polymer gels.Fig.1 shows the schematic of the 3D gel printer with the main component. The printer is based on a three cartesian axes system that allows the movement on the horizontal plane of the laser head and the vertical translation of the build platform. The axes are driven by NEMA 23 Stepper motors coupled with motor drivers (TMC2208). The build platform is made of the stainless steel or polyethylene terephthalate with the mesh structure which can supply the pre-gel solution on the build platform every layers.   The selectively curing reaction of pre-gel solution layer-by layer happens at the above surface of pre-gel solution using inexpensive UV laser. This 3D printing approach is generally called surface approach. The attractive forces by the surface approach are less than the constrained approach such as the system using liquid crystal display (LCD) photomask and digital light processing (DLP).

The open-source electronics for the system include the controller board (MKS gen 1.4) integrated Arduino Mega2560 and Ramps1.4 connected with the motor drivers (TMC2208), Raspberry Pi B+ module connected with webcam and lcd screen, the circuit MOSFET transistor for turning on/off UV laser and 12 Vdc/6.25 A power supply. A publicly available modification of open-source Marlin firmware (v1.19) [3] is loaded into the controller board to control the turning on/ off the UV laser with adding custom G-code.

To enhance the system with online access, the webserver based on the Raspberry Pi running an open-source application, the Octoprint, is connected to the controller board. The Octoprint provides a web interface to remotely message and operate the 3D printer. Thus, the 3D gel printer can be controlled and be monitored from any location through mobile and computer devices with any operating systems (Microsoft Windows, Apple MacOS, Linux, Android, etc.).

The open-source 3D gel printer can generate complex structures with setting of optimal printing parameters, as shown in Fig.2. In order to fabricate hollow structures, we controlled the parameters of material composition and the motion of 3D gel printer. The 3D gel printer can reach print resolutions closer to around 300 µm.

Moreover, we report our plans using the 3D gel printers for the purpose of co-creation in soft matter engineering. One is the collaborative research with companies participating the "Soft 3D Co-creation Consortium" (https://soft3d-c.jp) that we established in April 2018. We plant to share the practical use cases of hydrogels and how to use the 3D gel printers among the consortium members. Another one is the education course of the art classes. Through the workshop using 3D gel printers for high school students, we found 3D gel printers have the possibility of to encourage their creativity and critical thinking.