bioPrint: A Liquid Deposition Printing System for Natural Actuators

This article presents a digital fabrication platform for depositing solution-based natural stimuli-responsive material on a thin flat substrate to create hygromorphic biohybrid films. Bacillus subtilis bacterial spores are deposited in the printing process. The hardware system consists of a progressive cavity pump fluidic dispenser, a numerical control gantry, a cooling fan, a heating bed, an agitation module, and a camera module. The software pipeline includes the design of print patterns, simulation of resulting material transformations, and communication with computer hardware. The hardware and software systems are highly modularized and can therefore be easily reconfigured by the user. Biological Actuators and Digital Fabrication Recent studies in material science and mechanical engineering have investigated new classes of materials that output dynamic shapes. Shape memory alloys, shape memory polymers, electroactive polymers, and pneumatic soft actuators have been introduced as emerging material platforms for designers with which to create applications beyond medical and robotic fields. Looking to nature for inspiration, the wilting of flowers and the opening of fallen pinecones have, among others, served as inspiration for the design of biological sensors and actuators. The utilization of such mechanisms from nature via the integration of natural microorganisms into design and engineering processes has gained increasing interest among scientists and engineers. Some research projects, including ours, have explored the use of natural microorganisms as sensors and actuators. To fully explore the potential of these materials, digital fabrication processes and pipelines are presented. The ability to arrange material structures at different scales allows us to preprogram material transformations under certain stimuli. In particular, bioprinting represents an emerging technology for the construction and fabrication of biomaterials for research in bioengineering. Most of the current bioprinting technologies are inkjet and extrusion based. Inkjet printers enable precise control over the location of droplets and thus provide great flexibility to the user. For details about the hardware technology involved in this approach, numerous research articles are available that demonstrate a step-by-step approach for integrating an inkjet head with a CNC router. Despite the significant progress in inkjet-based bioprinting, this technique still faces some limitations. One of the main restrictions is the maximum printable viscosity of bioink. Cell aggregation and sedimentation in the cartridge and clogging of the nozzles are additional limitations associated with this technique. The method that uses a pressureor extrusion-based printing system has been applied for some time. Extrusion-basedbioprinting consists of a pneumatic or mechanical fluiddispensing system feeding an extruder on an automated robotic gantry. This method overcomes the viscosity limitation and clogging problem present in the inkjet system. However, there is often a trade-off in terms of the precision of printing. In this article, we introduce an open hardware and software platform for printing suspended Bacillus subtilis spores to pattern humidity-responsive nanosensors and actuators for local material shape transformation. Design Space with Micro–Macro Biology New and emerging engineering and computational components in the study of biology are of increasing relevance for the design community. We examine the biological performance at different scales and identify a novel design space that bridges the micro (cellular level) and macro (human level) scales. While synthetic biology primarily focuses on the nanoscale engineering of DNA, biological science MIT Media Lab, Department of Architecture, and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts. 3D PRINTING AND ADDITIVE MANUFACTURING Volume 2, Number 4, 2015 a Mary Ann Liebert, Inc. DOI: 10.1089/3dp.2015.0033