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The development of electronic skin (e-skin) is of great importance in human-like robotics, healthcare, wearable electronics, and medical applications. In this paper, a bioinspired e-skin design of hierarchical micro- and nano-structured ZnO nanowire (NW) arrays in an interlocked geometry is suggested for the sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. The interlocked hierarchical structures enable a stress-sensitive variation in the contact area between the interlocked ZnO NWs and also the efficient bending of ZnO NWs, which allow the sensitive detection of both static and dynamic tactile stimuli. The flexible e-skin in a piezoresistive mode shows a high pressure sensitivity (−6.8 kPa−1) and an ultrafast response time (<5 ms), which enables the detection of minute static pressure (0.6 Pa), vibration level (0.1 m s−2), and sound pressure (≈57 dB). The flexible e-skin in a piezoelectric mode is also demonstrated to be able to detect fast dynamic stimuli such as high frequency vibrations (≈250 Hz). The flexible e-skins with both piezoresistive and piezoelectric sensing capabilities may find applications requiring both static and dynamic tactile perceptions such as robotic hands for dexterous manipulations and various healthcare monitoring devices. [ABSTRACT FROM AUTHOR]

Viologen‐based reactive mesogen (VRM) is newly designed and synthesized for the development of polarization‐dependent, color‐tunable, and transparent electrochromic (EC) smart windows. By controlling electric field, the color of VRM can be intentionally tuned due to the formation of dication (D state), cation‐radical (C state), and neutral state (N state). Based on the deep understanding of phase transition of VRM, a uniaxially oriented VRM hierarchical nanostructure is successfully constructed on the macroscopic area by simple coating and self‐assembly processes. The subsequent photopolymerization significantly improves thermal, mechanical, and chemical stabilities of the VRM thin film. In addition to the control of color, the transmittance of uniaxially oriented VRM‐based EC smart window can be precisely tuned by rotating a linear polarizer. [ABSTRACT FROM AUTHOR]

To develop smart ionic skins capable of multi‐responsiveness and switchable ionic conductivity, a stimuli‐responsive and ionic conductive azobenzene‐based monomer is newly synthesized, uniaxially oriented, and polymerized for anisotropic liquid crystal elastomers (LCEs). Since the uniaxially oriented monodomain LCE with ionic asymmetric azobenzene monomers (i‐AAM) is prepared by thermal oligomerization, uniaxial stretching, and subsequent photopolymerization, the stimuli‐responsive i‐AAM LCE is thermally contracted by increasing the temperature above TNI as well as is bent along the aligned direction by irradiating it with UV light. In addition to the change of shape, the ionic conductivity of the LCE is reversible in response to heat and light stimuli. Polydomain i‐AAM LCE polymerized without the stretching process exhibits higher ionic conductivity than stretched monodomain LCE due to the initially formed stable ionic pathways. Ionic conductivity can also be switched simultaneously by polarity changes in response to the photoisomerization of i‐AAM, increased mobility from heat, and an elastic mechanoresponse from external stresses. These i‐AAM LCE‐based soft grippers exhibit stimuli‐responsive grasping and releasing actuation and detect ionic conductivity switches finely, suggesting potential as smart skins for advanced soft robots. [ABSTRACT FROM AUTHOR]

Organic–inorganic perovskites with micro‐/nanostructures exhibit outstanding optical and electrical properties, thus attracting increased attention as components of high‐performance optoelectronic devices, but the fabrication of complex micro‐/nanostructured perovskites shows limited success. This study describes the fabrication of hierarchical methylammonium lead iodide (MAPbI3) nanoribbon (NR) arrays with controlled internal nanorod structures by simple spin‐coating with solvent treatment process and investigates the suitability of these arrays for high‐performance and multifunctional photodetectors. In the UV‐to‐800‐nm range, photodetectors based on the hierarchical MAPbI3 NR arrays exhibit specific detectivities 18.1–23.7 times higher than those of photodetectors based on MAPbI3 films due to the effective photon management and reduced charge trap states in the hierarchical MAPbI3 NR arrays. The solution‐processed hierarchical MAPbI3 NRs can be fabricated on various substrates including ultrathin polyimide, which facilitates the development of flexible photodetectors with highly stable photoresponse under bending strain. Furthermore, the ferroelectricity and the highly anisotropic alignment of MAPbI3 NR arrays allow multifunctional photodetectors capable of self‐powered and polarization‐sensitive light detection, respectively. The strategy used to fabricate hierarchical organic–inorganic perovskite NR arrays is believed to be applicable to other types of perovskites and can probably be used to construct various optoelectronic devices based on hierarchical nanostructures. Hierarchical perovskite nanoribbon arrays with controlled internal nanorod structures are fabricated for high‐performance and flexible photodetectors with enhanced light absorption as well as reduced charge trap states. Furthermore, the ferroelectricity and highly anisotropic alignment of perovskite nanoribbon arrays provide self‐powered and polarization‐sensitive light‐detection capabilities. [ABSTRACT FROM AUTHOR]

Printed electronics are attractive due to their low-cost and large-area processing features, which have been successfully extended to magnetoresistive sensors and devices. Here, we introduce and characterize a new kind of magnetoresistive paste based on the anisotropic magnetoresistive (AMR) effect. The paste is a composite of 100-nm-thick permalloy/tantalum flakes embedded in an elastomer matrix, which promotes the formation of appropriately conductive percolation networks. Sensors printed with this paste showed stable magnetoresistive properties upon mechanical bending. The AMR value of this sensor is 0.34 % in the field of 400 mT. Still, the response is stable and allows to resolve sub-mT field steps. When printed on ultra-thin 2.5- μ m -thick Mylar foil, the sensor can be completely folded without losing magnetoresistive performance and mechanically withstand 20 μ m bending radius. The developed compliant printed AMR sensor would be attractive to implement on curved and/or dynamic bendable surfaces for on-skin applications and interactive printed electronics. [ABSTRACT FROM AUTHOR]

Flexible electronic skins (e‐skins) with static and dynamic tactile sensing capabilities are demonstrated on page 2841 by H. Ko and co‐workers based on the interlocked geometry of hierarchical polydimethylsiloxane (PDMS) micopillar arrays decorated with ZnO nanowire forests. While the e‐skin in a piezoresistive mode enables a static pressure detection with high sensitivity, the piezoelectric e‐skin mode permits the dynamic sensing of high frequency vibrations. [ABSTRACT FROM AUTHOR]

In the article "Ionic Conductivity Switchable and Shape Changeable Smart Skins with Azobenzene-Based Ionic Reactive Mesogens," researchers Kwang-Un Jeong and colleagues discuss the development of a new type of smart skin using a synthesized azobenzene-based ionic monomer. This liquid crystal elastomer (LCE) is capable of shape-changing and has switchable ionic conductivity. The researchers suggest that this new material could be used as a multi-responsive and reversible smart actuator and ionic skin for soft robotic applications. [Extracted from the article]

[Display omitted] • A novel way to fabricate long thin thread analogous liquid metal core shell fiber. • Vacuum assisted filling combined with room temperature plastic deformation. • Thread-like stretchable & robust fibers integrated to clothing to realize e-apparels. Stretchable and elastic conductive fibers with liquid metal core are appealing for integration into electronic fabrics and clothing, owing to their inherent electrical conductivity even under strain. Previously, injecting liquid metal into core of hollow elastic fiber has been utilized to fabricate conductive fibers, however, hydrodynamics limits the extent to which metals can be injected, thus limiting length and cross-sectional area. Although direct printing and spinning methods using coaxial needles have been utilized to fabricate long and thin polymer-encased liquid metal fibers via single step, various parameters including extrusion rate along with viscosity and surface tension of liquid metal and polymeric shell, needs to be considered. Herein, we introduce a simple and facile method for fabricating thread analogous conductive fibers by plastically deforming liquid metal injected polymeric shell via drawing at room temperature. This simple yet effective process generates long conductive fibers with narrow cross-sectional area of the liquid metal wire continuously formed along its length. The obtained fiber can withstand deformation arising from daily activities while maintaining excellent electrical performance, thus can be used for fabricating smart textiles serving multitude of purposes. [ABSTRACT FROM AUTHOR]