Photolithographic patterning and mechanical characterization of electrodeposited cellulose nanofiber composite microstructures

Cellulose nanofibers (CNFs) have attracted considerable attention as sustainable materials for microsystems and microdevices owing to their low density, high mechanical strength, and biodegradability. However, integrating CNFs into such systems requires patterning techniques compatible with photolithography. In this study, we present an electrodeposition-based “electroforming” method for fabricating free-standing CNF microstructures. Mechanically fibrillated CNFs were co-deposited with carboxymethyl cellulose (CMC), producing dense composite films. Nanoindentation measurements revealed a Young’s modulus of 4.2 GPa for the CNF/CMC films. Photolithography-enabled patterning produced CNF composite micropatterns and suspended CNF composite bridges with thicknesses as low as 300 nm. Mechanical vibration measurements under vacuum revealed a fundamental resonance at 23.34 kHz with a quality factor of 39. The high resonance frequency is consistent with an effective tensile stress likely introduced by constrained shrinkage during the pre-release hot-plate drying steps. These results demonstrate a scalable microfabrication approach for CNF-based microdevices, paving the way for biodegradable resonators, sensors, and electronic components.