Flexible biomimetic block copolymer composite for temperature and long-wave infrared sensing

Bio-inspired multimodal soft grippers: a review

In nature, organisms have evolved diverse grasping mechanisms to perform vital functions such as hunting and self-defence. These time-tested biological structures, including the arms of octopuses and the trunks of elephants, offer valuable inspiration for designing multimodal soft grippers that can tackle diverse tasks in various environments. Similar to their biological counterparts, these grippers must adapt to dynamic working conditions to enhance their performance. This adaptation process involves multiple factors, including grasping mechanisms, structural design, materials, and application scenarios, with biomimetic strategies offering numerous innovative examples. Despite the significant potential of bio-inspired designs, it lacks comprehensive reviews that explore how these strategies can enhance the development of multimodal soft grippers. This review seeks to address this gap by providing a systematic review of how bioinspired approaches contribute to the advancement of multimodal grippers. It focuses on coupling strategies, integration methods, performance improvements, and application scenarios. Finally, the review explores how future biomimetic insights could address current challenges and further improve the functionality of multimodal grippers.

Cationic-anionic synchronous ring-opening polymerization

Chemical reactions with incompatible mechanisms (such as nucleophilic reactions and electrophilic reactions, cationic polymerization and anionic polymerization) are usually difficult to perform simultaneously in one-pot. In particular, synchronous cationic-anionic polymerization has been an important challenge in the field of polymer synthesis due to possible coupling termination of both chain ends. We recently found that such terminal couplings can be significantly inhibited by a bismuth salt with a strong nucleophilic anion (e.g., BiCl3) and disclosed the mechanism. Accordingly, we propose a cationic-anionic polymerization (CAP) method where cationic ring-opening polymerization (CROP) of 2-oxazolines (Ox) and anionic ring-opening polymerization (AROP) of cyclic esters (CE) can be initiated sequentially and propagated simultaneously in one-pot, using bismuth salts as the initial initiators, to afford a multifunctional copolymer polyoxazoline-block-polyester (POx-b-PCE). Furthermore, a block copolymer PAPOZ20-b-PCL5 synthesized by CAP can self-assemble into micellar aggregates, which exhibit excellent intrinsic antibacterial activities without loading any extra antibiotic components. Overall, such a CAP method opens new avenues for synthesizing multi-component copolymers and biomaterials.

Advances in flexible ionic thermal sensors: present and perspectives

Ionic thermal sensors (ITSs) represent a promising frontier in sensing technology, offering unique advantages over conventional electronic sensors. Comprising a polymer matrix and electrolyte, these sensors possess inherent flexibility, stretchability, and biocompatibility, allowing them to establish stable and intimate contact with soft surfaces without inducing mechanical or thermal stress. Through an ion migration/dissociation mechanism similar to biosensing, ITSs ensure low impedance contact and high sensitivity, especially in physiological monitoring applications. This review provides a comprehensive overview of ionic thermal sensing mechanisms, contrasting them with their electronic counterparts. Additionally, it explores the intricacy of the sensor architecture, detailing the roles of active sensing elements, stretchable electrodes, and flexible substrates. The decoupled sensing mechanisms for skin-inspired multimodal sensors are also introduced based on several representative examples. The latest applications of ITS are categorized into ionic skin (i-skin), healthcare, spatial thermal perception, and environment detection, regarding their materials, structures, and operation modes. Finally, the perspectives of ITS research are presented, emphasizing the significance of standardized sensing parameters and emerging requirements for practical applications.

Probing the ionic activation enthalpies in anionic polysaccharide xerogel-based single ion conductor for temperature sensing

Ionic charge transport in polymer-based solid electrolytes is significantly affected by thermal perturbations, facilitating the detection of temperature variations. However, the impact of ionic interactions and molecular arrangements in polymeric single-ion conductors (SICs) has not been thoroughly investigated for temperature sensing. By probing the effect of the associated energies for ionic interactions and polymeric rearrangements, the thermal sensing characteristics of alginate have been studied. For the first time, alginate SIC interacting with multivalent ions (viz., Na+, Ca2+ and Fe3+) to form xerogel has been exploited as a temperature-sensing layer by fabricating a xerogel-based ionic thermistor (xIT) as a temperature sensor. The xIT has demonstrated stable functioning from 25 to 70 °C and unveiled enhanced sensing abilities in the physiological state of the human body (35-40 °C), exhibiting a monotonic linear response, high sensitivity (-3.77 % °C-1), and high accuracy (0.1 °C). The sensing characteristic is observed due to the inward ionic flux under thermal and electrical perturbations. The concentration of ionic charge carriers and ionic drift are assumed to be Arrhenius-activated processes. A general microscopic model of ion transport within polysaccharides has been elucidated via hopping mechanisms, and the effects of the associated activation energies on temperature sensitivity have been explained.

Molecular control via dynamic bonding enables material responsiveness in additively manufactured metallo-polyelectrolytes

Metallo-polyelectrolytes are versatile materials for applications like filtration, biomedical devices, and sensors, due to their metal-organic synergy. Their dynamic and reversible electrostatic interactions offer high ionic conductivity, self-healing, and tunable mechanical properties. However, the knowledge gap between molecular-level dynamic bonds and continuum-level material properties persists, largely due to limited fabrication methods and a lack of theoretical design frameworks. To address this critical gap, we present a framework, combining theoretical and experimental insights, highlighting the interplay of molecular parameters in governing material properties. Using stereolithography-based additive manufacturing, we produce durable metallo-polyelectrolytes gels with tunable mechanical properties based on metal ion valency and polymer charge sparsity. Our approach unveils mechanistic insights into how these interactions propagate to macroscale properties, where higher valency ions yield stiffer, tougher materials, and lower charge sparsity alters material phase behavior. This work enhances understanding of metallo-polyelectrolytes behavior, providing a foundation for designing advanced functional materials.

Bismuth-Based Perovskite Derivates with Thermal Voltage Exceeding 40 mV/K

Heat is an inexhaustible source of energy, and it can be exploited by thermoelectronics to produce electrical power or electrical responses. The search for a low-cost thermoelectric material that could achieve high efficiencies and can also be straightforwardly scalable has turned significant attention to the halide perovskite family. Here, we report the thermal voltage response of bismuth-based perovskite derivates and suggest a path to increase the electrical conductivity by applying chalcogenide doping. The films were produced by drop-casting or spin coating, and sulfur was introduced in the precursor solution using bismuth triethylxanthate. The physical-chemical analysis confirms the substitution. The sulfur introduction caused resistivity reduction by 2 orders of magnitude, and the thermal voltage exceeded 40 mV K-1 near 300 K in doped and undoped bismuth-based perovskite derivates. X-ray diffraction, Raman spectroscopy, and grazing-incidence wide-angle X-ray scattering were employed to confirm the structure. X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed to study the composition and morphology of the produced thin films. UV-visible absorbance, photoluminescence, inverse photoemission, and ultraviolet photoelectron spectroscopies have been used to investigate the energy band gap.

Ultraflexible Wireless Imager Integrated with Organic Circuits for Broadband Infrared Thermal Analysis

Flexible imagers are currently under intensive development as versatile optical sensor arrays, designed to capture images of surfaces and internals, irrespective of their shape. A significant challenge in developing flexible imagers is extending their detection capabilities to encompass a broad spectrum of infrared light, particularly terahertz (THz) light at room temperature. This advancement is crucial for thermal and biochemical applications. In this study, a flexible infrared imager is designed using uncooled carbon nanotube (CNT) sensors and organic circuits. The CNT sensors, fabricated on ultrathin 2.4 µm substrates, demonstrate enhanced sensitivity across a wide infrared range, spanning from near-infrared to THz wavelengths. Moreover, they retain their characteristics under bending and crumpling. The design incorporates light-shielded organic transistors and circuits, functioning reliably under light irradiation, and amplifies THz detection signals by a factor of 10. The integration of both CNT sensors and shielded organic transistors into an 8 × 8 active-sensor matrix within the imager enables sequential infrared imaging and nondestructive assessment for heat sources and in-liquid chemicals through wireless communication systems. The proposed imager, offering unique functionality, shows promise for applications in biochemical analysis and soft robotics.

Ultrasensitive Flexible Temperature Sensors Based on Thermal-Mediated Ions Migration Dynamics in Asymmetrical Polymer Bilayers

Accurately acquiring crucial data on the ambient surroundings and physiological processes delivered via subtle temperature fluctuation is vital for advancing artificial intelligence and personal healthcare techniques but is still challenging. Here, we introduce an electrically induced cation injection mechanism based on thermal-mediated ion migration dynamics in an asymmetrical polymer bilayer (APB) composed of nonionic polymer and polyelectrolyte layers, enabling the development of ultrasensitive flexible temperature sensors. The resulting optimized sensor achieves ultrahigh sensitivity, with a thermal index surpassing 10,000 K-1, which allows identifying temperature differences as small as 10 mK with a sensitivity that exceeds 1.5 mK. The mechanism also enables APB sensors to possess good insensitivity to various mechanical deformations─features essential for practical applications. As a proof of concept, we demonstrate the potential impact of APB sensors in various conceptual applications, such as mental tension evaluation, biomimetic thermal tactile, and thermal radiation detection.

Biomimetic Wearable Sensors: Emerging Combination of Intelligence and Electronics

Owing to the advancement of interdisciplinary concepts, for example, wearable electronics, bioelectronics, and intelligent sensing, during the microelectronics industrial revolution, nowadays, extensively mature wearable sensing devices have become new favorites in the noninvasive human healthcare industry. The combination of wearable sensing devices with bionics is driving frontier developments in various fields, such as personalized medical monitoring and flexible electronics, due to the superior biocompatibilities and diverse sensing mechanisms. It is noticed that the integration of desired functions into wearable device materials can be realized by grafting biomimetic intelligence. Therefore, herein, the mechanism by which biomimetic materials satisfy and further enhance system functionality is reviewed. Next, wearable artificial sensory systems that integrate biomimetic sensing into portable sensing devices are introduced, which have received significant attention from the industry owing to their novel sensing approaches and portabilities. To address the limitations encountered by important signal and data units in biomimetic wearable sensing systems, two paths forward are identified and current challenges and opportunities are presented in this field. In summary, this review provides a further comprehensive understanding of the development of biomimetic wearable sensing devices from both breadth and depth perspectives, offering valuable guidance for future research and application expansion of these devices.