Programmable Self‐Regulation with Wrinkled Hydrogels and Plasmonic Nanoparticle Lattices

Abstract

This paper describes a self‐regulating system that combines wrinkle‐patterned hydrogels with plasmonic nanoparticle (NP) lattices. In the feedback loop, the wrinkle patterns flatten in response to moisture, which then allows light to reach the NP lattice on the bottom layer. Upon light absorption, the NP lattice produces a photothermal effect that dries the hydrogel, and the system then returns to the initial wrinkled configuration. The timescale of this regulatory cycle can be programmed by tuning the degree of photothermal heating by NP size and substrate material. Time‐dependent finite element analysis reveals the thermal and mechanical mechanisms of wrinkle formation. This self‐regulating system couples morphological, optical, and thermo‐mechanical properties of different materials components and offers promising design principles for future smart systems.

Patterning meets gels: Advances in engineering functional gels at micro/nanoscales for soft devices

“…89 More recently, Odom group described a self-regulation system combining responsive wrinkle-patterned PAM hydrogel coating with plasmonic metal nanoarrays (Figure 9B). 90 The wrinkles could be modulated to appear and vanish during dry and moisture conditions, in which the flattened surface allowed light to reach the nanoparticle lattice, producing photothermal effect that again dried the hydrogel to return the wrinkled and opaque state.…”

“…Adapted with permission. 90 Copyright 2021 John Wiley and Sons. (C) Optical image of activated carbon thin film coated on smooth and microstructured hydrogel surface under 100% strain, demonstrating the reduced cracks by the microstructured interface.…”

“…(B) A self‐regulating system consists of (a) microscale wrinkle‐patterned PAM hydrogel at the top layer and (b) plasmonic nanoparticle lattice at the bottom layer, permitting the feedback loop between the hydrogel and the lattice components, where each step involves a sensing (S) and an actuating (A) mechanism related with moisture and light. Adapted with permission 90 . Copyright 2021 John Wiley and Sons.…”

Engineering Viscoelasticity in Autoregulatory Nanoscale Wrinkling Bilayer Hydrogel Systems: Pressure Sensors and Thermal-Responsive Drug Delivery Systems

“…Wrinkle formation due to mechanical instabilities is widely used, with applications to tunable temporal autoregulatory systems, flexible electronics, , cell growth controlling substrates, , microcontact printing stamps, photolithography masks, , pressure sensors, and chemical sensors . In general, the nanoscale or microscale surface patterns that result from wrinkling enable control of optical (e.g., scattering and transmitting of light ,, ), chemical (e.g., hydrophobicity − ), and physical (e.g., roughness , ) properties of layered surfaces. Hence, predicting and controlling the pattern of nanoscale wrinkles such as their wavelength and amplitude is of utmost importance.…”

“…In recent studies, ,− ,, the soft layer has usually been modeled as linear elastic material for simplification and preventing convergence issues but at the expense of losing viscous features of the hydrogel. Utilizing more realistic material models would enable a reliable characterization of the bilayer composite systems for a wide range of material properties.…”