Variable impedance energy dissipation on the micro-scale : field responsive fluids in novel geometries

Abstract

The aim of this thesis was to further characterize the effectiveness of field responsive fluids (FRFs) in geometries pertinent to the soldier and to examine the effects of specific geometric and kinematic parameters, including patterned surface geometry, electrode gap distance, and normal force on the performance of homogeneous ERF composites. Field responsive fluid composites designed for variable impedance energy absorption incorporated electrorheological fluid (ERF) and shear-thickening fluid (STF) in novel geometries to absorb compressive and tensile/shear forces. ER and ST fluids change their apparent viscosity in the presence of elevated electric and shear fields, respectively, and the magnitude of this effect can be adjusted using the magnitude of the input field, allowing variable impedance operation. Several test fixtures were developed to test these novel FRF composites. A compression apparatus was designed and constructed to test STF-filled foam over a range of strain rates not previously examined in the literature. Silicon-based microchannel devices with etched features on the order of 100 pm and etch depths of 7-90 pm were fabricated to test homogeneous ER fluids in small electrode gaps.

(cont.) Tests using these silicon devices allowed creation of 5 kV/mm (5 V/pm) electric fields across electrode gaps as small as 20 pm, with increases of measured shear force as high as 350% from no electric field to full 5 kV/mm operation. Production of these devices in bulk using established silicon processing techniques was demonstrated, and factors affecting the manufacture of these devices were investigated.