More Like this

1. Preprogrammed Dynamic Microstructured Polymer Interfaces

   https://doi.org/10.1002/adfm.201903478  

   Tokarev, Igor; Minko, Sergiy (August 2019, Advanced Functional Materials)

   Abstract The advancement of new‐generation complex integrated responsive systems depends on the progress in the development of functional stimuli‐responsive polymer components that could be put together and engineered to perform in concert as an ensemble. This progress report highlights recent substantial progress in the development of such soft‐matter components capable of changes according to preprogrammed scenarios. The components interact via interfaces that play a key role in the performance of the microstructured materials. The list of the most important properties that can be changed by altering the interfaces upon external stimuli includes gating, transport, release, wetting, adhesion, and self‐regeneration (healing) realized in different architectures of soft stimuli‐responsive materials. 

   more » « less
2. Controlling the Spatiotemporal Self-Organization of Stimuli-Responsive Nanocrystals under Out-of-Equilibrium Conditions

   https://doi.org/10.1021/jacs.4c11195  

   Damacet, Patrick; Shehayeb, Elissa O; Mirica, Katherine A (January 2025, Journal of the American Chemical Society)

   Self-organization under out-of-equilibrium conditions is ubiquitous in natural systems for the generation of hierarchical solid-state patterns of complex structures with intricate properties. Efforts in applying this strategy to synthetic materials that mimic biological function have resulted in remarkable demonstrations of programmable self-healing and adaptive materials. However, the extension of these efforts to multifunctional stimuli-responsive solidstate materials across defined spatial distributions remains an unrealized technological opportunity. This paper describes the use of a nonequilibrium reaction−diffusion process to achieve the synthesis of a multifunctional stimuli-responsive electrically conductive metal−organic framework (cMOF) in a gelled medium with control over particle size and spatial periodicity on a macroscopic scale. Upon integration into chemiresistive devices, the resulting cMOF particles exhibit a size-dependent response toward hydrogen sulfide gas, as determined by their distinct surface-to-volume ratio, porosity, unique synthesis methodology, and unusual microcrystallite morphology compared to their counterparts obtained through bulk solution phase synthesis. Taken altogether, these achievements pave the way toward gaining access to functional nanomaterials with well-defined chemical composition, dimensions, and precisely tailored functions using far-from-equilibrium approaches. 

   more » « less
3. From design to applications of stimuli-responsive hydrogel strain sensors

   https://doi.org/10.1039/C9TB02692D  

   Zhang, Dong; Ren, Baiping; Zhang, Yanxian; Xu, Lijian; Huang, Qinyuan; He, Yi; Li, Xuefeng; Wu, Jiang; Yang, Jintao; Chen, Qiang; et al (April 2020, Journal of Materials Chemistry B)

   null (Ed.)

   Stimuli-responsive hydrogel strain sensors that synergize the advantages of both soft-wet hydrogels and smart functional materials have attracted rapidly increasing interest for exploring the opportunities from material design principles to emerging applications in electronic skins, health monitors, and human–machine interfaces. Stimuli-responsive hydrogel strain sensors possess smart and on-demand ability to specifically recognize various external stimuli and convert them into strain-induced mechanical, thermal, optical, and electrical signals. This review presents an up-to-date summary over the past five years on hydrogel strain sensors from different aspects, including material designs, gelation/fabrication methods, stimuli-responsive principles, and sensing performance. Hydrogel strain sensors are classified into five major categories based on the nature of the stimuli, and representative examples from each category are carefully selected and discussed in terms of structures, response mechanisms, and potential medical applications. Finally, current challenges and future perspectives of hydrogel strain sensors are tentatively proposed to stimulate more and better research in this emerging field. 

   more » « less
4. Dynamic Coordination of Eu–Iminodiacetate to Control Fluorochromic Response of Polymer Hydrogels to Multistimuli

   https://doi.org/10.1002/adma.201706526  

   Weng, Gengsheng; Thanneeru, Srinivas; He, Jie (January 2018, Advanced Materials)

   Abstract New fluorochromic materials that reversibly change their emission properties in response to their environment are of interest for the development of sensors and light‐emitting materials. A new design of Eu‐containing polymer hydrogels showing fast self‐healing and tunable fluorochromic properties in response to five different stimuli, including pH, temperature, metal ions, sonication, and force, is reported. The polymer hydrogels are fabricated using Eu–iminodiacetate (IDA) coordination in a hydrophilic poly(N,N‐dimethylacrylamide) matrix. Dynamic metal–ligand coordination allows reversible formation and disruption of hydrogel networks under various stimuli which makes hydrogels self‐healable and injectable. Such hydrogels show interesting switchable ON/OFF luminescence along with the sol–gel transition through the reversible formation and dissociation of Eu–IDA complexes upon various stimuli. It is demonstrated that Eu‐containing hydrogels display fast and reversible mechanochromic response as well in hydrogels having interpenetrating polymer network. Those multistimuli responsive fluorochromic hydrogels illustrate a new pathway to make smart optical materials, particularly for biological sensors where multistimuli response is required. 

   more » « less
5. Stimuli responsive Janus microgels with convertible hydrophilicity for controlled emulsion destabilization

   https://doi.org/10.1039/d0sm00255k  

   Haney, Bobby; Werner, Jörg G.; Weitz, David A.; Ramakrishnan, Subramanian (April 2020, Soft Matter)

   null (Ed.)

   Although the utilization of rigid particles can afford stable emulsions, some applications require eventual emulsion destabilization to release contents captured in the particle-covered droplet. This destabilizing effect is achieved when using stabilizers that respond to controlled changes in environment. Microgels can be synthesized as stimuli responsive polymeric gel networks that adsorb to oil/water interfaces and stabilize emulsions. These particles are commonly hydrogels that swell and collapse in water in response to environmental changes. However, amphiphilic functionality is desired to enhance the adsorption abilities of these hydrogels while maintaining their stimuli responsivity. Microfluidic techniques are used to synthesize Janus microgels with two opposing stimuli responsive hemispheres. The particles have a temperature responsive domain connected to a pH responsive network where each side changes its hydrophilicity in response to a change in temperature or pH, respectively. The Janus microgels are amphiphilic in acidic conditions at 19 °C and alkaline conditions at 40 °C, while the opposite conditions cause a reduction of the amphiphilicity. By stabilizing emulsions with these dual responsive microgels, “smart” droplets that respond to environmental cues are formed. Emulsion droplets remain stable with smaller diameters when aqueous solution conditions favor amphiphilic particles yet, coalesce to larger droplets upon changing pH or temperature. These responsive Janus microgels represent the advancing technology of responsive droplets and demonstrate the applicability of microgels as emulsion stabilizers. 

   more » « less