DESIGN, FABRICATION, AND APPLICATIONS OF POROUS ELASTOMERS FOR COMPLIANT FLUIDICALLY POWERED MACHINES

Abstract

Open-celled elastomer foams enable many new designs for fluidically inflated, soft machines. These foams allow for simple fabrication of complex shapes containing an embedded fluidic network, without the requirement of laborious molding or assembly necessary for other common fabrication methods. In the first part of this work, a method is described to produce porous silicone via a lost salt process that allows porosity to be easily tuned. This process also allows the silicone to be molded into a variety of geometries, while retaining an interconnected porous network. Porosity is shown to affect foam mechanical properties and actuator performance. Additionally, the flow rate of air through foam samples is characterized with flow studies and X-ray computed tomography, then compared to a theoretical model. To demonstrate the unique geometries possible with this material system, a heart-inspired, compliant water pump is presented that provides pulsatile flow at physiologically relevant frequencies and pressures. Next, a buckled polyurethane foam system is described. Actuator characterization reveals that a moderate amount of residual compressive strain augments the applied force or the maximum stroke compared with uncompressed actuators. These actuators are applied in a patient-specific direct cardiac compression (DCC) device design. The compliant DCC device is demonstrated on a porcine heart and is capable of assisting heart pumping at systolic and diastolic durations and physiological stroke volumes. Finally, a compliant haptic interface is developed for virtual reality interactions. The interface is demonstrated in the form of an internally porous controller handle that can change stiffness and shape when pressurized, simulating the physical shape and feel of different virtual objects. The elastomeric handle is composed of an internal lattice network which was selected from an array of geometries with corresponding finite element simulations that compare their buckling. As an additional method of interaction, compressions of the handle are demonstrated as a means of user input.