Biocompatible Soft Fluidic Strain and Force Sensors for Wearable Devices

Fluidic soft sensors have been widely used in wearable devices for human motion capturing. However, thus far, the biocompatibility of the conductive liquid, the linearity of the sensing signal, and the hysteresis between the loading and release processes have limited the sensing quality as well as the applications of these sensors. In this paper, silicone based strain and force sensors composed of a novel biocompatible conductive liquid (potassium iodide and glycerol solution) are introduced. The strain sensors exhibit negligible hysteresis up to 5 Hz, with a gauge factor of 2.2 at 1 Hz. The force sensors feature a novel multifunctional layered structure, with microcylinder‐filled channels to achieve high linearity, low hysteresis (5.3% hysteresis at 1 Hz), and good sensitivity (100% resistance increase at a 5 N load). The sensors' gauge factors are stable at various temperatures and humidity levels. These biocompatible, low hysteresis, and high linearity sensors are promising for safe and reliable diagnostic devices, wearable motion capture, and compliant human–computer interfaces.     

Self-Healing Photochromic Elastomer Composites for Wearable UV-Sensors (Adv. Funct. Mater. 20/2023)

Photochromic materials have recently received strong interest for the development of wearable ultraviolet (UV) detection technologies because they do not require electronic components, resulting in systems and devices that change color upon irradiation. However, their implementation in wearable technology has lightweight, compliance, and durability (especially under mechanical stress) requirements that are limited by the materials’ properties. Here, a self-healing photochromic elastomer composite (photoPUSH) consisting of phosphomolybdic acid (PMA) in a self-healing polyurethane dynamic network with reversible disulfide bonds (PUSH) is presented. The unique properties of the dynamic polymer matrix enable multiple complementary functions in the UV-sensing composite: i) photochromism via electron donor groups without requiring additional dopants, ii) stretchability and durability via elastomeric properties, iii) healing of extreme mechanical damage via dynamic bonds, and iv) multimaterial integration via adhesive properties. PhotoPUSH composites exhibit excellent durability, tunable sensing range, and no loss of performance under mechanical stress and severe damage, as well as in underwater environments (waterproof). Leveraging these properties, soft, portable, multimaterial photoPUSH-based UV-sensing devices are developed for applications in environmental monitoring, packaging, and healthcare wearable technology (including skin-mounted, textile-mounted, and wristband devices) in challenging environments and tunable to different skin types.     

All-Organic Smart Textile Sensor for Deep-Learning-Assisted Multimodal Sensing (Adv. Funct. Mater. 30/2023)

Smart textile for sensor is identified as a superior platform with greatly improved convenience and comfort for wearable bioelectronics. However, most reported textile-based sensors cannot fully demonstrate the inherent advantages of textiles, such as comfortability, breathability, biocompatibility, and environmental friendliness, mainly due to the intrinsic limitation of non-textile or inorganic components. Here, an all-textile, all-organic, washable, and breathable sensor with discriminable pressure, proximity, and temperature sensing function is first reported. Multiple sensing functions and outstanding washability are demonstrated. The all-textile sensor can also be seamlessly integrated into diverse types of fabrics to realize wide-range sensing of human activities and noncontact stimuli without sacrificing biocompatibility and comfortability. Additionally, by combining with the deep-learning technique, an all-textile sensing system is established to recognize object shape, contactless trajectory, and even environmental temperature. These results open a new avenue for designing low-cost, washable, comfortable, and biocompatible green textile electronics, providing a meaningful guideline in intelligent textiles.