A new design strategy for mechanoresponsive materials with high thermal tolerance

Phys.org  September 11, 2023 Radical type mechanophores (RMs), molecules that can undergo small-scale chemical reactions upon exposure to a mechanical stimulus are studied due to their potential application in the fabrication of highly functionalized polymers. However, the lack of a rational design concept with pre-determined properties limits their development. Researchers in Japan have developed a rational design strategy of RMs with high thermal tolerance while maintaining mechanoresponsiveness. Through experimental and theoretical analysis, they found that the high thermal tolerance of RMs is related to the radical-stabilization energy (RSE) as well as the Hammett and modified Swain–Lupton constants at the para-position. […]

‘Countercation engineering’ for thermoresponsive graphene-oxide nanosheets

Phys.org   August 31, 2023 Thermoresponsive graphene-oxide (GO) nanosheets have been widely employed to develop smart membranes/surfaces, hydrogel actuators, recyclable systems, and biomedical applications. Current synthetic strategies to generate thermoresponsive GO nanosheets have exclusively relied on the covalent or non-covalent modification of their surfaces with thermoresponsive polymers. Researchers in Japan discovered that GO nanosheets with Bu4N+ countercations became thermoresponsive in water without the use of any thermoresponsive polymers, inducing a reversible sol–gel transition via their self-assembly and disassembly processes. The resultant dispersion can be used as a direct writing ink for constructing a three-dimensionally designable gel architecture of the GO nanosheets. […]

New programmable smart fabric responds to temperature and electricity

Phys.org  April 24, 2023 To study multi-stimuli-responsive materials with distinctive abilities to change color and color-changing and shape-memory, an international team of researchers (China, Canada) wove an electrothermally multi-responsive fabric using metallic composite yarns and polymeric/thermochromic microcapsule composite fibers. The shape-memory and color-changing features of the fabric could be controlled by rationally controlling the micro-scale design of the individual fibers in the structure. The microstructural features were optimized to achieve excellent color-changing behavior along with shape fixity and recovery ratios of 99.95% and 79.2%, respectively. The fabric’s dual response by electric field could be achieved by a low voltage of […]

Researchers discover new process to create freestanding membranes of ‘smart’ materials

Phys.org  January 3, 2023 The aggressive oxidizing conditions typically used in growing epitaxial oxides can damage graphene. A team of researchers in the US (University of Minnesota, Pacific Northwest National Laboratory, University of Wisconsin) used hybrid molecular beam epitaxy for SrTiO3 growth that did not require an independent oxygen source, thus avoided graphene damage. They produced epitaxial films with self-regulating cation stoichiometry. The film could be exfoliated and transferred to foreign substrates. The results opened the door to future studies of previously unattainable freestanding oxide nanomembranes grown in an adsorption-controlled manner by hybrid molecular beam epitaxy. According to the researchers […]

Designing self-assembling ‘smart materials’

Science Daily  December 12, 2022 The role of hydrodynamic interactions (HIs) play in the self-organization of colloidal suspensions and biological solutions has remained elusive particularly for charged soft matter systems. Researchers in Japan studied the role of HIs in the self-assembly of oppositely charged colloidal particles, which is a promising candidate for electrical tunable soft materials. In many-body HIs and the coupling between the colloid, ion, and fluid motions they found that, under a constant electric field, oppositely charged colloidal particles formed clusters and percolated into a gel network. They revealed that the cluster-forming tendency originates from the incompressibility-induced “inverse […]

Next generation material that adapts to its history

Nanowerk  November 15, 2022 The responses of living systems dynamically adapt based on the repetition, intensity, and history of stimuli. Such plasticity is ubiquitous in biology, which is profoundly linked to memory and learning. Inspired by living systems, researchers in Finland synthesised micrometre-sized magnetic beads which were then stimulated by a magnetic field. When the magnet was on, the beads stacked up to form pillars. The strength of the magnetic field affects the shape of the pillars, which in turn affects how well they conduct electricity. When they exposed the beads to a quickly pulsing magnetic field, the material became […]

Multisensory hybrid material as smart electronic skin

Nanowerk  May 16, 2022 Researchers in Austria proposed a simplified design with biocompatible materials for an efficient electronic skin. They demonstrated that it can deliver multi-stimuli sensitivity with high spatial resolution. While the piezoelectricity of ZnO provided sensitivity to external force, the thermoresponsiveness of the hydrogel core provided sensitivity to surrounding temperature and humidity changes. The hydrogel core exerted mechanical stress onto the ZnO shell, which was translated to a measurable piezoelectric signal. A localized force sensitivity was achieved with very low cross talk. They demonstrated the sensor’s sensitivity to humidity was above and below the hydrogel’s lower critical solution […]

Tunable smart materials

Science Daily  March 22, 2021 Biological molecules in living organisms have a remarkable ability to form self-assembled structures when triggered by an external molecule. Based on this concept researchers in Japan created a tunable system involving poly(sodium acrylate) microparticles that can have one of two types of chemical groups attached. The adjustable parameters x and y refer to the molar percent of microparticles with β-cyclodextrin and adamantyl residues, respectively. The shape of assemblies formed by microparticles was dependent on the residue content. For assemblies to form, x needed to be at least 22.3. As the value of y increased, the […]

Controlled by light alone, new smart materials twist, bend and move

Science Daily  March 12, 2021 The ability to topographically control photonic bandgaps allows programmable actuation of the elastomeric substrate in response to illumination. An international team of researchers (USA – Tufts University, Northwestern University, Italy) combined programmable photonic function with elastomeric material composites to generate optomechanical actuators that display controllable and tunable actuation as well as complex deformation in response to simple light illumination. They developed complex three-dimensional configurations, programmable motion patterns, and phototropic movement where the material moves in response to the motion of a light source. A “photonic sunflower” demonstrator device consisting of a light-tracking solar cell was […]

New textile could keep you cool in the heat, warm in the cold

Phys.org  April 1, 2020 Researchers in China freeze-spun silk and chitosan, a material from the hard outer skeleton of shellfish, into colored fibers with porous microstructures. They filled the pores with polyethylene glycol (PEG), a phase-changing polymer that absorbs and releases thermal energy. The threads were coated with polydimethylsiloxane to keep the liquid PEG from leaking out. The resulting fibers were strong, flexible, and water-repellent. To test the fibers, the researchers wove them into a patch of fabric and put inside a polyester glove. When a person wearing the glove placed their hand in a hot chamber (122°F), the solid […]