A bio-inspired, chemo-responsive polymer nanocomposite for mechanically dynamic microsystems

This paper reports the development of a biologically-inspired, variable-modulus nanocomposite material for mechanically dynamic biomedical microsystems. This nanocomposite is comprised of a poly(vinyl acetate) matrix polymer that is reinforced with rigid cellulose nanofibers, and becomes very flexible when exposed to water. A direct-write CO₂ laser was used to pattern structures in this chemical- and temperature-sensitive material. Tensile testing of laser-cut, micron-scale nanocomposite beams was performed using a custom-built tensile tester. These samples displayed a significant reduction in Young´s modulus from 4.1 GPa to 6.1 MPa when the nanocomposite was exposed to phosphate buffered saline. Additionally, the modulus change was observed to be reversible upon drying of soaked tensile samples. As a well-suited application of this nanocomposite, cortical probes utilizing this material as a substrate were fabricated. Gold-coated, dual-shank cortical probes utilizing this nanocomposite as a substrate were shown to record action potentials from a single neuron in a cockroach brain.