Competitive Bidirectional Response in Bi‐Polymeric Mechanochromic Cantilevers Toward Color Imaging‐Based VOC Discrimination

Abstract The detection of VOCs is essential for environmental monitoring, industrial safety, and medical diagnostics applications. Developing VOC sensors that intrinsically generate multidimensional responses has become especially relevant, as it can significantly reduce reliance on complex multisensor arrays for effective VOC discrimination. Herein, bi‐polymeric mechanochromic cantilevers composed of polydimethylsiloxane (PDMS) and off‐stoichiometry thiol‐ene‐epoxy (OSTE+) intrinsically generate competitive bidirectional response patterns is demonstrated through material‐specific interactions with VOCs. Differential swelling between the two polymers induces a competitive bidirectional bending response and corresponding color changes, with three characteristic response modes related to the Hansen solubility parameters (HSPs) of the VOCs: OSTE+‐driven bending for VOCs with low dispersion and moderate‐to‐high hydrogen‐bonding and polarity parameters, PDMS‐mediated bending for those with moderate‐to‐high dispersion and low‐to‐moderate hydrogen‐bonding and polarity, and mixed bending for VOCs with intermediate HSPs. By leveraging these combined swelling dynamics, the bi‐polymeric mechanochromic cantilevers enable solubility‐reporting, sensitive, color‐imaging‐based VOC detection using a single sensor type and detection mode.