Mechanical behavior of microstructures from a chemo-responsive polymer nanocomposite based on cotton cellulose nanofibers

This paper reports on the fabrication and characterization of MEMS-scale devices from a mechanically dynamic polymer nanocomposite, consisting of a cotton-derived cellulose nanofibers encased in a poly(vinyl acetate) matrix, with a stiffness modulated by the presence or absence of water. Microtensile testing showed that the Young´s modulus (E) of the nanocomposite is initially ~2.7 GPa, but reduces to ~4 MPa upon immersion in water for 7 minutes. A combination of laser-micromachining and lithographic processing was used to produce an intracortical probe with switchable stiffness based on the dynamic nanocomposite. An electrode with area 2800 μm² was found to have an impedance of 156 kΩ at 1 kHz. This investigation was the first time that a chemoresponsive nanocomposite based on cotton cellulose nanofibers was used in MEMS-scale structures.