Soft conductors are created by embedding liquid metal nanoparticles between two elastomeric sheets. Initially, the particles form an electrically insulating composite. Soft circuit boards can be handwritten by a stylus, which sinters the particles into conductive traces by applying localized mechanical pressure to the elastomeric sheets. Antennas with tunable frequencies are formed by sintering nanoparticles in microchannels.

1605630(1 of 8) temperature, and low viscosity. The latter property allows LM to flow in response to deformation, whereas solid metals are stiff and prone to fail at small strains. Embedding LM in elastomer decouples the electrical and mechanical properties; that is, these composites have the electrical properties of the metal and the mechanical properties of the elastomer. Incorporating the LM into the hollow core of an elastomeric fiber results in a useful form for sensors because fibers may be integrated into clothing and fabrics. [12][13][14][15] Furthermore, fibers are inherently flexible, compliant, and conformal due to their narrow cross-section. Thus, fibers can readily wrap onto and conform to surfaces with Gaussian curvature whereas 2D sheets cannot without significant deformation. Fibers can also be mass produced at high speeds with small diameters (hundreds of microns) and produced by hand in a laboratory environment at room temperature. [16] The fibers described in this work have the additional advantage of being built from stretchable and soft materials. Fibers with LM cores have previously been used to make light-emitting structures [17] and stretchable wires that retain metallic conductance up to ≈800% strain. [18] We reasoned that elastomeric fibers filled with LM could also be used for capacitive sensing of torsion, strain, and touch.Here, we intertwined two fibers into a double-helix to create sensors of both torsion and strain since twisting or stretching the fibers increases the contact area between them, and therefore changes the capacitance. The complexity of torsion, which causes both normal and shear strain, has previously precluded the development of a simple sensor capable of measuring a large range of torsion. Existing torsion sensors measure changes in normalized resistance, [2,8,19,20] pressure, [9] and optical properties, [21] or utilize surface acoustic waves [22] or the inverse magnetostrictive effect. [23] Some of these sensors can detect changes as small as 0.3 rad m −1 and can measure torsion up to 800 rad m −1 before failure. Most existing torsion sensors, however, are rigid, cumbersome, expensive, and complex. The soft and stretchable sensor developed here offers a simple mechanism to measure large changes in torsion which may be useful for unconventional robotics [24,25] or artificial muscles. [26] In addition to sensing torsion, intertwined fibers increase capacitance in response to strain due to the increase in contact Soft and stretchable sensors have the potential to be incorporated into soft robotics and conformal electronics. Liquid metals represent a promising class of materials for creating these sensors because they can undergo large deformations while retaining electrical continuity. Incorporating liquid metal into hollow elastomeric capillaries results in fibers that can integrate with textiles, comply with complex surfaces, and be mass produced at high speeds. Liquid metal is injected into the core of hollow and extremely stretchable elastomeric fibers and the re...

Dye-sensitized solar cells (DSCs) are a next-generation photovoltaic technology, whose natural transparency and good photovoltaic output under ambient light conditions afford them niche applications in solar-powered windows and interior design for energy-sustainable buildings. Their ability to be fabricated on flexible substrates, or as fibers, also makes them attractive as passive energy harvesters in wearable devices and textiles. Cosensitization has emerged as a method that affords efficiency gains in DSCs, being most celebrated via its role in nudging power conversion efficiencies of DSCs to reach world-record values; yet, cosensitization has a much wider potential for applications, as this review will show. Cosensitization is a chemical fabrication method that produces DSC working electrodes that contain two or more different dyes with complementary optical absorption characteristics. Dye combinations that collectively afford a panchromatic absorption spectrum emulating that of the solar emission spectrum are ideal, given that such combinations use all available sunlight. This review classifies existing cosensitization efforts into seven distinct ways that dyes have been combined in order to generate panchromatic DSCs. Seven cognate molecular-engineering strategies for cosensitization are thereby developed, which tailor optical absorption toward optimal DSC-device function.

Shape memory polymers are promising materials in many emerging applications due to their large extensibility and excellent shape recovery. However, practical application of these polymers is limited by their poor energy densities (up to ∼1 MJ/m 3 ). Here, we report an approach to achieve a high energy density, one-way shape memory polymer based on the formation of strain-induced supramolecular nanostructures. As polymer chains align during strain, strong directional dynamic bonds form, creating stable supramolecular nanostructures and trapping stretched chains in a highly elongated state. Upon heating, the dynamic bonds break, and stretched chains contract to their initial disordered state. This mechanism stores large amounts of entropic energy (as high as 19.6 MJ/m 3 or 17.9 J/g), almost six times higher than the best previously reported shape memory polymers while maintaining near 100% shape recovery and fixity. The reported phenomenon of strain-induced supramolecular structures offers a new approach toward achieving high energy density shape memory polymers.

Data‐driven materials discovery has become increasingly important in identifying materials that exhibit specific, desirable properties from a vast chemical search space. Synergic prediction and experimental validation are needed to accelerate scientific advances related to critical societal applications. A design‐to‐device study that uses high‐throughput screens with algorithmic encodings of structure–property relationships is reported to identify new materials with panchromatic optical absorption, whose photovoltaic device applications are then experimentally verified. The data‐mining methods source 9431 dye candidates, which are auto‐generated from the literature using a custom text‐mining tool. These candidates are sifted via a data‐mining workflow that is tailored to identify optimal combinations of organic dyes that have complementary optical absorption properties such that they can harvest all available sunlight when acting as co‐sensitizers for dye‐sensitized solar cells (DSSCs). Six promising dye combinations are shortlisted for device testing, whereupon one dye combination yields co‐sensitized DSSCs with power conversion efficiencies comparable to those of the high‐performance, organometallic dye, N719. These results demonstrate how data‐driven molecular engineering can accelerate materials discovery for panchromatic photovoltaic or other applications.