Mussel‐Inspired Flexible, Wearable, and Self‐Adhesive Conductive Hydrogels for Strain Sensors

An amylopectin-enabled skin-mounted hydrogel wearable sensor

Self-adhesiveness is highly desirable for conformal and seamless wearable electronics.

A review of the properties and applications of bioadhesive hydrogels

Due to their outstanding properties, bioadhesive hydrogels have been extensively studied by researchers in recent years.

Flexible Self-Repairing Materials for Wearable Sensing Applications: Elastomers and Hydrogels

Flexible pressure and strain sensors have great potential for applications in wearable and implantable devices, soft robots, and artificial skin. The introduction of self-healing performance has made a positive contribution to the lifetime and stability of flexible sensors. At present, many self-healing flexible sensors with high sensitivity have been developed to detect the signal of organism activity. The sensitivity, reliability, and stability of self-healing flexible sensors depend on the conductive network and mechanical properties of flexible materials. This review focuses on the latest research progress of self-healing flexible sensors. First, various repair mechanisms of self-healing flexible materials are reviewed because these mechanisms contribute to the development of self-healing flexible materials. Then, self-healing elastomer flexible sensor and self-healing hydrogel flexible sensor are introduced and discussed respectively. The research status and problems to be solved of these two types of flexible sensors are discussed in detail. Finally, this rapidly developing and promising field of self-healing flexible sensors and devices is prospected.

Printed, Soft, Nanostructured Strain Sensors for Monitoring of Structural Health and Human Physiology

Soft strain sensors that are mechanically flexible or stretchable are of significant interest in the fields of structural health monitoring, human physiology, and human-machine interfaces. However, existing deformable strain sensors still suffer from complex fabrication processes, poor reusability, limited adhesion strength, or structural rigidity. In this work, we introduce a versatile, high-throughput fabrication method of nanostructured, soft material-enabled, miniaturized strain sensors for both structural health monitoring and human physiology detection. Aerosol jet printing of polyimide and silver nanowires enables multifunctional strain sensors with tunable resistance and gauge factor. Experimental study of soft material compositions and multilayered structures of the strain sensor demonstrates the capabilities of strong adhesion and conformal lamination on different surfaces without the use of conventional fixtures and/or tapes. A two-axis, printed strain gauge enables the detection of force-induced strain changes on a curved stem valve for structural health management while offering reusability over 10 times without losing the sensing performance. Direct comparison with a commercial film sensor captures the advantages of the printed soft sensor in enhanced gauge factor and sensitivity. Another type of a stretchable strain sensor in skin-wearable applications demonstrates a highly sensitive monitoring of a subject's motion, pulse, and breathing, validated by comparing it with a clinical-grade system. Overall, the presented comprehensive study of materials, mechanics, printing-based fabrication, and interfacial adhesion shows a great potential of the printed soft strain sensor for applications in continuous structural health monitoring, human health detection, machine-interfacing systems, and environmental condition monitoring.

Mussel-Inspired Biocoating for Improving the Adhesion of Dental Pulp Stem Cells in Dental Pulp Regeneration

Dental pulp engineering possesses a promising perspective to replacing lost pulp in the root canal and restoring its functions. Stable adhesion of dental pulp stem cells (DPSCs) on the root canal dentin wall is a key element required for reconstruction of a functional odontoblast layer in dental pulp regeneration. To address this challenge, dopamine-modified hyaluronic acid (DA-HA) is coated on dentin to obtain a stable adhesion of DPSCs. The dopamine segment provides adhesion ability to the coating, and the hyaluronic acid increases the biocompatibility. The results show that DPSCs can adhere on the DA-HA coated dentin slice better than those without coating. Simultaneously, DPSCs proliferation can be further promoted on the prepared coating. Therefore, the DA-HA coating may provide a possible way to immobilize odontoblast cell onto dentin surface for pulp regeneration.

Multifunctional composite hydrogel bolus with combined self-healing, antibacterial and adhesive functions for radiotherapy

TPU/PAAm hydrogel with excellent mechanical, adhesive, self-healing and antibacterial properties has been successfully prepared as a desirable bolus for radiotherapy.