Freeform Fabrication of Complete Devices: Compact Manufacturing for Human and Robotic Exploration

Abstract

[Abstract] Solid Freeform Fabrication (SFF) refers to a to a family of manufacturing processes, sometimes also referred to as Rapid Prototyping (RP), Additive Manufacturing, or Layered Manufacturing, which can produce almost arbitrarily shaped structures directly from computer-aided design (CAD) data, by computer-controlled deposition or solidification of material. These technologies have traditionally been developed and employed for the production of passive mechanical parts of a single material. Advances in this technology and in materials science make it feasible to develop a single, compact SFF system – including a small set of materials which can automatically produce complete, active, functional electromechanical devices. In the long term, such systems may evolve into low-waste, extremely flexible, compact factories to enable space exploration, and will offer access to a set of electromechanical device designs in which geometry and performance can be continuously varied to achieve optimal and/or otherwise unrealizable products. One of the major challenges associated with the exploration and development of space is the high cost of production and delivery of equipment and supplies to the location being explored. The high cost of launch systems is the most obvious contributor, in part because within the current paradigm of exploration, the mass of productive materiel applied to the site of exploration is roughly the same as the mass of materiel launched from earth. As a result of this paradigm, the extreme cost of developing the equipment to be deployed – including tools, instrumentation, exploration robotics, etc. – has been difficult to reduce. Each object to be delivered must withstand the rigors of launch and possibly also entry, descent and landing, a great deal of effort is required to ensure that the payload does not constitute a hazard to the delivery vehicle, equipment must be designed to operate in largely unknown circumstances, and all of this must be achieved with a minimum of mass. In Situ Manufacturing (ISM) capability, such as may be provided by an SFF-based compact factory, will permit massive multiplication of the utility of materiel mass delivered to the site of exploration. Only the factory itself and the raw materials it consumes need to accommodate the launch and delivery constraints. The products of the factory can be tailored to the immediate need and conditions and need not be over-designed. Recycling of materials and design of the factory to employ in situ resources will further leverage delivered mass, with the result that each launch from earth contributes to an exploration and development infrastructure, rather than simply depositing a disposable scientific payload. We are developing an SFF-based compact factory (1m) capable of autonomous manufacture of complete electromechanical devices. For simplicity, the system uses primarily polymeric and soft materials with low temperature processes. We have already demonstrated with our prototype system: freeform fabrication of thermoplastic and elastomer structures and flexures, freeform fabrication of Pb-Sn and Ag-ink conductive wiring embedded in structural materials, the first freeform fabrication of complete zinc-air batteries, the first freeform fabrication of Ionomeric Polymer-Metal Composite (IPMC) actuators, and the first freeform fabrication of elastomer strain gages. In addition, a collaborative effort has led to the “net shape” fabrication of alginate hydrogel tissue scaffolds directly from computed tomography (CT) data, and the fabrication of living tissue constructs consisting of chondrocyte cells in alginate hydrogel. Current work is focused on using the system to produce transistors based on organic semiconductors, and on improving the yield, quality, and predictability of devices produced