Pressure-sensing films with enhanced pressure responsivity: Cellulose microfiber films containing mechanochromic fluorenylidene-acridane

Reusable pressure-sensing films were developed using the ground-state mechanochromic compound fluorenylidene-acridane (FA) and cellulose fibers with different morphologies. FA exhibits reversible color changes under mechanical pressure, enabling visual detection of pressure distribution. In this study, FA–cellulose composite films were fabricated using cellulose nanofibers (CNF) and cellulose microfibers (CMF) to investigate the influence of fiber morphology and network structure on pressure responsivity. Among the prepared samples, FA/CMF composite films exhibited the highest pressure responsivity and the widest measurable pressure range. The films detected pressures as low as 2 MPa and showed a clear correlation between applied pressure and the cyan coloration ratio over the range of 2–300 MPa. Structural analyses indicated that the branched micro–nano architecture of CMF forms a porous network with strong interfacial adhesion to FA particles, facilitating efficient stress transfer within the composite. These findings demonstrate that optimizing cellulose fiber morphology and network structure is an effective strategy for enhancing the performance of mechanochromic pressure-sensing films.