Freeform Fabrication of Ionomeric Polymer-Metal Composite Actuators

Ionomeric polymer-metal composite (IPMC) actuators are a type of soft electromechanically active material which offers large displacement, rapid motion with only ~1V stimulus. IPMC’s are entering commercial applications in toys (Ashley 2003) and biomedical devices (Soltanpour 2001; Shahinpoor 2002; Shahinpoor, Shahinpoor et al. 2003; Soltanpour and Shahinpoor 2003; Soltanpour and Shahinpoor 2004), but unfortunately they can only actuate by bending, limiting their utility. Freeform fabrication offers a possible means of producing IPMC with novel geometry and/or tightly integrated with mechanisms which can yield linear or more complex motion. We have developed materials and processes which allow us to freeform fabricate complete IPMC actuators and their fabrication substrate which will allow integration within other freeform fabricated devices. We have produced simple IPMC’s using our multiple material freeform fabrication system, and have demonstrated operation in air for more than 40 minutes and 256 bidirectional actuation cycles. The output stress scaled to input power is two orders of magnitude inferior to that of the best reported performance for devices produced in the traditional manner, but only slightly inferior to devices produced in a more similar manner. Possible explanations and paths to improvement are presented. Freeform fabrication of complete electroactive polymer actuators in unusual geometries, with tailored actuation behavior, and integrated with other freeform fabricated active components, will enable advances in biomedical device engineering, biologically inspired robotics, and other fields. This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.Mechanical Engineerin

Tunable Digital Material Properties of 3D Voxel Printers

Digital materials are composed of many discrete voxels placed in a massively parallel layer deposition process, as opposed to continuous (analog) deposition techniques. We explore the material properties attainable using a voxel-based freeform fabrication process and simulate how the properties can be tuned for a wide range of applications. By varying the precision, geometry, and material of the individual voxels, we obtain continuous control over the density, elastic modulus, CTE, ductility, and failure mode of the material. Also, we demonstrate the effects of several hierarchical voxel “microstructures”, resulting in interesting properties such as negative poisson’s ratio. This implies that digital materials can exhibit widely varying properties in a single desktop fabrication process.Mechanical Engineerin

Freeform Fabrication of Electroactive Polymer Actuators and Electromechanical Devices

In pursuit of the goal of producing complete electromechanical systems entirely via solid freeform fabrication, we are developing a library of mutually compatible, functional, freeform elements. Several essential elements – actuation, sensing, and control electronics - still remain to be incorporated into this library. Conducting polymers (CP) are a class of materials which can be used to produce all of these functionalities. Meanwhile, research into actuatable “smart” materials has produced other candidate materials for freeform fabricated actuators that are compatible with our library. We have succeeded in manually producing air-operable actuators that have processing and operating requirements that are compatible with our power source and mechanical component library elements. A survey of candidate actuator materials is presented, experiments performed with two types of actuator materials are described, and complete SFF-producible actuator devices are demonstrated.Mechanical Engineerin

Methods of Parallel Voxel Manipulation for 3D Digital Printing

A novel digital printing concept is explored for desktop fabrication of multimaterial objects with arbitrary 3D geometry. Digital objects are composed of many discrete, self-aligning voxels instead of continuous (analog) deposition techniques. Overall accuracy is determined by the individual voxels instead of the printer, and digital properties such as perfect replication and error correction are physically meaningful. The key challenge in digital printing is massively parallel, deterministic voxel manipulation. To quickly print millions of voxels while keeping errors low, we propose a parallel manufacturing process that exploits electrostatic forces to place an entire 2D pattern of voxels concurrently. Using a custom charged print head, we demonstrate selective 1.5mm voxel pick-up within a larger, self-aligned layer. We expect the principle to scale to million voxel layers using currently available technology.Mechanical Engineerin

Printing Embedded Circuits

Automated manufacturing technologies such as freeform fabrication can greatly reduce the cost and complexity of infrastructure required to manufacture unique devices or invent new technologies. Multi-material freeform fabrication processes under development have the potential to automatically build complete functional devices including electronics. Making this technology available to creative individuals will revolutionize art and invention, but requires extensive simplification and cost reduction of what is still a laboratory technology. The combination of a Fab@Home Model 1 personal fabrication system and commercially available materials allows the demonstration of simple and inexpensive freeform fabrication of functional embedded electrical circuits, and useful devices. Using this approach, we have been able to demonstrate an LED flashlight, functional printed circuit boards in 2-dimensions and 3- dimensions that are actually entirely printed, and a child’s toy with embedded circuitry. These results, and the materials and methods involved in producing them will be presented in detail.Mechanical Engineerin