Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics

Retrospective Analysis of Structure-Property Relationship of Emergent Metallo-Supramolecular Polymer Networks

Metallo-supramolecular polymer networks (MSPNs) are fabricated from the crosslinking of polymers by discrete supramolecular coordination complexes. Due to the availability of various coordination complexes, e. g., 2D macrocycles and 3D nanocages, the MSPNs have been recently developed with broadly tunable visco-elasticity and enriched functions inherited from the coordination complexes. The coordination complexes possess enriched topologies and unique structural relaxation dynamics, rendering them the capability to break the traditional tradeoffs of polymer systems for the design of materials with enhanced mechanical performance. The structure-property relationship studies are critical for the material-by-design of MSPNs, while the spatiotemporal investigations are desired for the exploration of dynamics information. The work summarizes recent studies on the unique ligand-exchange kinetics and the multi-level structural relaxation dynamics of MSPNs. The MSPNs' mechanical properties can be quantitatively correlated with the dynamics for understanding the structure-property relationship. This concept will not only serve to attract more researchers to engage in the study of the structure-activity relationship of MSPNs but also inspire innovative research findings pertaining to the application of MSPNs.

Voltage-tunable elastomer composites that use shape instabilities for rapid structural color changes

Structurally colored materials can switch colors in response to external stimuli, which makes them potentially useful as colorimetric sensors, dynamic displays, and camouflage. However, their applications are limited by the angular dependence, slow response, and absence of synchronous control in time and space. In addition, out-of-plane deformation from shape instability easily occurs in photonic films, leading to inhomogeneous colors in photonic-crystal materials. To address these challenges, we combine structurally colored photonic glasses and dielectric elastomer actuators. We use an external voltage signal to tune color changes quickly (much less than 0.1 s). The photonic glassses produce colors with low angular dependence, so that their colors are homogeneous even when they become curved due to voltage-triggered instabilities (buckling or wrinkling). As proof of concept, we present a pixelated display in which segments can be independently and rapidly turned on and off. This wide-angle, instability-tolerant, color-changing platform could be used in next-generation soft and curved color displays, camouflage with both shape and color changes, and multifunctional sensors.

Multifunctional coating of cotton fabric via the assembly of amino-quinone networks with polyamine biomacromolecules and dopamine quinone

Functional textiles with antibacterial properties and UV protection are essential for human health. However, the process of functional modification of textiles is usually done with the help of chemical cross-linking agents to improve the bonding fastness of functional finishing agents on textiles. The use of chemical cross-linking agents is not eco-friendly enough and is prone to chemical waste. In this study, some highly reactive polyamine biomolecules were combined with dopamine quinone, a super adhesive bionic material, to spontaneously construct amino-quinone networks (AQNs) coatings on the surface of cotton fabrics without the addition of chemical crosslinkers. The amino/quinone compounds (A/Q) self-crosslinking reaction is achieved by Michael addition and Schiff base reaction between the quinone group in dopamine quinone and the amino group in chitosan (CTS), chitooligosaccharide (COS) or ԑ-polylysine (ԑ-PL). The combination of polyamines and dopamine quinone during the cotton finishing process imparts antibacterial and UV protection to cotton fabric. The results showed that the AQNs coating modified fabrics had superb UV protection and antibacterial rates of over 96% against both E. coli and S. aureus. In addition, the AQNs coating modified fabrics had good resistance to washing and mechanical abrasion. This study proposes that self-assembled amino-quinone network multifunctional coatings of dopamine quinone and polyamine biomolecules are of guiding significance for the development of environmentally friendly bio-based materials.

Ultrafast volume holography for stretchable photonic structures

Stretchability and flexibility are two key requirements for manipulating the propagation of light in compact and high-performance lab-on-a-chip systems. These requirements are best met by embedding stretchable and flexible tuning elements such as volume phase gratings (VPGs) in polydimethylsiloxane (PDMS), making them attractive alternatives to conventional rigid optical elements. However, fabrication of these PDMS VPGs is a challenge, requiring extensive modifications to PDMS or complex multi-step processes that require long processing times. In this context, we propose the concept of "ultrafast volume holography" for the fabrication of stretchable photonic structures such as tunable VPGs directly in unmodified PDMS. Our concept translates insights in heat regulation via fs repetition rate control into volumetric patterning, forming periodic refractive index modulation of 1.95 × 10^-4 in the PDMS without post-processing. VPGs formed are further demonstrated as active beam steering units and tunable spectroscopic optical elements.

Elastic FRET sensors for contactless pressure measurement

Contactless pressure monitoring based on Förster resonance energy transfer between donor–acceptors pairs immobilized within a thermoplastic elastomer is demonstrated for novel stretchable opto-electronics and opto-mechanical sensors.