Active polymers, such as stimuli-responsive hydrogels, capable of changing volume and other properties upon environmental cues, have attracted broad interests in environment, biomedicine, and smart systems. Upon external stimuli such as moisture or specific chemical/biological molecules, gel thin films can rapidly change their thickness, resulting in an instant color change itself or the configuration change of the embedded microstructures. Here we present three functions: ‘hydrogel interferometer’ for chemical/bio-sensing, ‘hydrocipher’ for cryptographic surfaces, and chemo-mechanical molecule separation. First, the gel thin film’s stimuli-responsive color changing led to colorimetric sensors, producing optical read-out signals under ambient light and allowing for in-situ quantitative analysis by naked eye or camera via analysis app. It has shown ultra-sensitivity and good selectivity in detecting metal ions and proteins within 1-2 seconds. Second, coupling the stimuli-reversible refractive-index (mis)match of hydrogel and reconfigurable grating-based diffraction coloration from the embedded micropillar array enabled a complete encryption of the structural color and rapid decryption. A water-responsive 2D diffraction grating, termed “hydrocipher,” is developed as an optically cryptographic surface, based on micropillar array-embedded hydrogel. The on-demand reconfigurable grating enables the complete encryption and fast decryption of structural color patterns by the (de)hydration of the hydrogel. The film possesses good mechanical durability and allows for scalable fabrication, providing a pragmatic platform for user-interactive anti-counterfeiting tags. Third, the pH-responsive hydrogel can actuate the embedded pillars with their tips functionalized with aptamer, allowing for capturing target protein from a mixture fluid and subsequently releasing in a blank fluid, as a chemo-mechanical molecule sorting and concentration in microfluidic devices.<br/>

Stimuli-responsive hydrogel thin films for sensing, sorting, and cryptography

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.