Multiresponsive Dielectric Metasurfaces Based on Dual Light‐ and Temperature‐Responsive Copolymers

Abstract Tunability is essential for unlocking a range of practical applications of high‐efficiency metasurface‐based nanophotonic devices and systems. Increased research efforts in this area during recent years led to significant progress regarding tuning mechanisms, speed, and diverse active functionalities. However, so far almost all the demonstrated works are based on a single type of physical stimulus, thereby excluding important opportunities to enhance the modulation range of the metadevices, the available design options, as well as interaction channels between the metadevices and their environment. In this article, it is experimentally demonstrated that multi‐responsive metasurfaces can be realized by combining asymmetric, highly resonant metasurfaces with multi‐responsive polymeric materials. The respective copolymers combine light‐ and temperature‐responsive comonomers in an optimized ratio. This work demonstrates clearly reversible light‐responsive, temperature‐responsive, and co‐responsive tuning of the metasurface optical resonance positions at near‐infrared wavelengths, featuring maximum spectral resonance shifts of nearly twice the full‐width‐at‐half‐maximum and accompanied by more than 60% absolute modulation in transmittance. This work provides new design freedom for multifunctional metadevices and can potentially be expanded to other types of copolymers as well. Furthermore, the studied hybrid multiresponsive systems are promising candidates for multi‐dimensional sensing applications.Light and temperature‐responsive polymers are integrated with asymmetric silicon metasurfaces for dual‐responsive tuning of their transmittance. Reversible resonance shifts induced by light exposure, temperature changes or a combination of both stimuli are experimentally demonstrated. This work paves the way for multiresponsive metasurface components and is promising for multi‐dimensional interactive smart optical devices. imag

Double hydrophilic poly(ethylene glycol)-block-poly(dehydroalanine) four-arm star block copolymers: synthesis and solution behavior

Star-shaped block copolymers are of interest as versatile and highly functional polymeric building blocks and show interesting solution properties or self-assembly. Herein, we report the synthesis of novel, double hydrophilic four-arm star-shaped block copolymers, based on different poly(ethylene glycol) cores (PEG) and short lengths (“stickers“) of poly(dehydroalanine) (PDha). As PDha is a polyampholyte we were mainly interested in the pH-dependent behavior, which we characterize by dynamic light scattering (DLS), atomic force microscopy (AFM), potentiometric titration, and zeta potential measurements. Our main interest was to elucidate how the presence of a short (6-7 units) or intermediate (up to 41 units) PDha segment influences the solution properties of such double hydrophilic block copolymers depending on the solution pH. As we can show, even short “stickers” show a profound influence and lead to increasing aggregation tendency at low pH values, as demonstrated by DLS and AFM experiments with aggregate sizes beyond 1 µm