Self-Adaptive Perception of Object's Deformability with Multiple Deformation Attributes Utilizing Biomimetic Mechanoreceptors.

The perception of object's deformability in unstructured interactions relies on both kinesthetic and cutaneous cues to adapt the uncertainties of an object. However, the existing tactile sensors cannot provide adequate cutaneous cues to self-adaptively estimate the material softness, especially in non-standard contact scenarios where the interacting object deviates from the assumption of an elastic half-infinite body. This paper proposes an innovative design of a tactile sensor that integrates the capabilities of two slow-adapting mechanoreceptors within a soft medium, allowing self-decoupled sensing of local pressure and strain at specific locations within the contact interface. By leveraging these localized cutaneous cues, the sensor can accurately and self-adaptively measure the material softness of an object, accommodating variations in thicknesses and applied forces. Furthermore, when combined with a kinesthetic cue from the robot, the sensor can enhance tactile expression by the synergy of two relevant deformation attributes, including material softness and compliance. It is demonstrated that the biomimetic fusion of tactile information can fully comprehend the deformability of an object, hence facilitating robotic decision-making and dexterous manipulation.

Road Narrow-Inspired Strain Concentration to Wide-Range-Tunable Gauge Factor of Ionic Hydrogel Strain Sensor.

The application of stretchable strain sensors in human movement recognition, health monitoring, and soft robotics has attracted wide attention. Compared with traditional electronic conductors, stretchable ionic hydrogels are more attractive to organization-like soft electronic devices yet suffer poor sensitivity due to limited ion conduction modulation caused by their intrinsic soft chain network. This paper proposes a strategy to modulate ion transport behavior by geometry-induced strain concentration to adjust and improve the sensitivity of ionic hydrogel-based strain sensors (IHSS). Inspired by the phenomenon of vehicles slowing down and changing lanes when the road narrows, the strain redistribution of ionic hydrogel is optimized by structural and mechanical parameters to produce a strain-induced resistance boost. As a result, the gauge factor of the IHSS is continuously tunable from 1.31 to 9.21 in the strain range of 0-100%, which breaks through the theoretical limit of homogeneous strain-distributed ionic hydrogels and ensures a linear electromechanical response simultaneously. Overall, this study offers a universal route to modulate the ion transport behavior of ionic hydrogels mechanically, resulting in a tunable sensitivity for IHSS to better serve different application scenarios, such as health monitoring and human-machine interface.

Mechanically Interlocked Hydrogel-Elastomer Strain Sensor with Robust Interface and Enhanced Water-Retention Capacity.

Hydrogels are stretchable ion conductors that can be used as strain sensors by transmitting strain-dependent electrical signals. However, hydrogels are susceptible to dehydration in the air, leading to a loss of flexibility and functions. Here, a simple and general strategy for encapsulating hydrogel with hydrophobic elastomer is proposed to realize excellent water-retention capacity. Elastomers, such as polydimethylsiloxanes (PDMS), whose hydrophobicity and dense crosslinking network can act as a barrier against water evaporation (lost 4.6 wt.% ± 0.57 in 24 h, 28 °C, and ≈30% humidity). To achieve strong adhesion between the hydrogel and elastomer, a porous structured thermoplastic polyurethane (TPU) is used at the hydrogel-elastomer interface to interlock the hydrogel and bond the elastomer simultaneously (the maximum interfacial toughness is over 1200 J/m2). In addition, a PDMS encapsulated ionic hydrogel strain sensor is proposed, demonstrating an excellent water-retention ability, superior mechanical performance, highly linear sensitivity (gauge factor = 2.21, at 100% strain), and robust interface. Various human motions were monitored, proving the effectiveness and practicability of the hydrogel-elastomer hybrid.

A Flexible Multimodal Sole Sensor for Legged Robot Sensing Complex Ground Information during Locomotion.

Recent achievements in the field of computer vision, reinforcement learning, and locomotion control have largely extended legged robots' maneuverability in complex natural environments. However, little research focuses on sensing and analyzing the physical properties of the ground, which is crucial to robots' locomotion during their interaction with highly irregular profiles, deformable terrains, and slippery surfaces. A biomimetic, flexible, multimodal sole sensor (FMSS) designed for legged robots to identify the ontological status and ground information, such as reaction force mapping, contact situation, terrain, and texture information, to achieve agile maneuvers was innovatively presented in this paper. The FMSS is flexible and large-loaded (20 Pa-800 kPa), designed by integrating a triboelectric sensing coat, embedded piezoelectric sensor, and piezoresistive sensor array. To evaluate the effectiveness and adaptability in different environments, the multimodal sensor was mounted on one of the quadruped robot's feet and one of the human feet then traversed through different environments in real-world tests. The experiment's results demonstrated that the FMSS could recognize terrain, texture, hardness, and contact conditions during locomotion effectively and retrain its sensitivity (0.66 kPa-1), robustness, and compliance. The presented work indicates the FMSS's potential to extend the feasibility and dexterity of tactile perception for state estimation and complex scenario detection.

Flexible Piezoresistive Sensors with Wide-Range Pressure Measurements Based on a Graded Nest-like Architecture.

Flexible pressure sensors present great potential in the application of human health monitoring, tactile function of prosthesis, and electronic skin for robotics. These applications require different trade-off between the sensitivity and sensing range, therefore, it is imperative to develop range-specific sensitivities in a single sensor. In this paper, a bioinspired strategy for a resistive pressure sensor using a graded porous material is proposed to measure pressures from several pascals to megapascals. Its fabrication is based on an easily accessible template method. The nest-architecture-based wide-range pressure sensor exhibits adequate sensitivity under an extensive pressure regime (20 Pa to 1.2 MPa). In addition, with rational structural design and subtle engineering of the material properties, the sensor achieves remarkable mechanical stability. To prove the concept, sensors were attached on a bicycle wheel to monitor the tire-pavement pressure and on human skin to detect biosignals such as venous and arterial blood pressure pulses.

High-Performance Humidity Sensor Based on Urchin-Like Composite of Ti3C2 MXene-Derived TiO2 Nanowires.

Humidity sensors have broad applications in health monitoring, environmental protection and human-machine interface, and robotics. Here, we developed a humidity sensor using alkali oxidation method to grow in situ TiO2 nanowires on two-dimensional Ti3C2 MXene. With an order of magnitude larger surface area compared to pure Ti3C2 or TiO2 materials, the urchin-like Ti3C2/TiO2 composite demonstrates a record high sensitivity in a low relative humidity (RH) environment (∼280 pF/% RH from 7% RH to 33% RH). Complex impedance spectroscopy and Schottky junction theory were employed to understand the underlying sensing mechanisms of the Ti3C2/TiO2 composite under various humidity conditions. We demonstrate the application of humidity sensors made with the Ti3C2/TiO2 composite for noncontact detection of the presence of various liquids as well as human fingers.

A transcriptional and functional analysis of heat hardening in two invasive fruit fly species, Bactrocera dorsalis and Bactrocera correcta.

Many insects have the capacity to increase their resistance to high temperatures by undergoing heat hardening at nonlethal temperatures. Although this response is well established, its molecular underpinnings have only been investigated in a few species where it seems to relate at least partly to the expression of heat shock protein (Hsp) genes. Here, we studied the mechanism of hardening and associated transcription responses in larvae of two invasive fruit fly species in China, Bactrocera dorsalis and Bactrocera correcta. Both species showed hardening which increased resistance to 45°C, although the more widespread B. dorsalis hardened better at higher temperatures compared to B. correcta which hardened better at lower temperatures. Transcriptional analyses highlighted expression changes in a number of genes representing different biochemical pathways, but these changes and pathways were inconsistent between the two species. Overall B. dorsalis showed expression changes in more genes than B. correcta. Hsp genes tended to be upregulated at a hardening temperature of 38°C in both species, while at 35°C many Hsp genes tended to be upregulated in B. correcta but not B. dorsalis. One candidate gene (the small heat shock protein gene, Hsp23) with a particularly high level of upregulation was investigated functionally using RNA interference (RNAi). We found that RNAi may be more efficient in B. dorsalis, in which suppression of the expression of this gene removed the hardening response, whereas in B. correcta RNAi did not decrease the hardening response. The different patterns of gene expression in these two species at the two hardening temperatures highlight the diverse mechanisms underlying hardening even in closely related species. These results may provide target genes for future control efforts against such pest species.

Ionic Gels and Their Applications in Stretchable Electronics.

Ionic gels represent a novel class of stretchable materials where ionic conducting liquid is immobilized in a polymer matrix. This review focuses on the design of ionic gel materials and device fabrication of ionic-gel-based stretchable electronics. In particular, recent progress in ionic-gel-based electronic skin (pressure/strain sensors, electric double-layer transistors, etc.), flexible displays, energy storage devices, and soft actuators are summarized, followed by a discussion of challenges in developing ionic-gel-based electronics and suggestions for future research directions that might overcome those challenges.

Enhanced UV-Visible Light Photocatalytic Activity by Constructing Appropriate Heterostructures between Mesopore TiO2 Nanospheres and Sn3O4 Nanoparticles.

Novel TiO2/Sn3O4 heterostructure photocatalysts were ingeniously synthesized via a scalable two-step method. The impressive photocatalytic abilities of the TiO2/Sn3O4 sphere nanocomposites were validated by the degradation test of methyl orange and •OH trapping photoluminescence experiments under ultraviolet (UV) and visible light irradiation, respectively. Especially under the visible light, the TiO2/Sn3O4 nanocomposites demonstrated a superb photocatalytic activity, with 81.2% of methyl orange (MO) decomposed at 30 min after irradiation, which greatly exceeded that of the P25 (13.4%), TiO2 (0.5%) and pure Sn3O4 (59.1%) nanostructures. This enhanced photocatalytic performance could be attributed to the mesopore induced by the monodispersed TiO2 cores that supply sufficient surface areas and accessibility to reactant molecules. This exquisite hetero-architecture facilitates extended UV-visible absorption and efficient photoexcited charge carrier separation.

Interlinked multiphase Fe-doped MnO2 nanostructures: a novel design for enhanced pseudocapacitive performance.

Structure designing and morphology control can lead to high performance pseudocapacitive materials for supercapacitors. In this work, we have designed interlinked multiphase Fe-doped MnO2 nanostructures (α-MnO2/R-MnO2/ε-MnO2) to enhance the electrochemical properties by a facile method. These hierarchical hollow microspheres assembled by interconnected nanoflakes, and with plenty of porous nanorods radiating from the spherical shells were hydrothermally obtained. The supercapacitor electrode prepared from the unique construction exhibits outstanding specific capacitance of 267.0 F g(-1) even under a high mass loading (∼5 mg cm(-2)). Obviously improved performances compared to pure MnO2 are also demonstrated with a good rate capability, high energy density (1.30 mW h cm(-3)) and excellent cycling stability of 100% capacitance retention after 2000 cycles at 2 A g(-1). The synergistic effects of alternative crystal structures, appropriate crystallinity and optimal morphology are identified to be responsible for the observations. This rational multiphase composite strategy provides a promising idea for materials scientists to design and prepare scalable electrode materials for energy storage devices.