Waterproof fiber-based strain sensors with a high gauge factor and outstanding stability are essential for smart textiles, wearable devices and biomedical electronics. In this work, we demonstrate a highly flexible, stretchable, sensitive, and waterproof core-sheath structure strain sensor with a relatively wide strain-sensing range fabricated by a simple approach. Such a core-sheath structure is composed of a superelastic core material polyurethane (PU) yarn; a highly conductive multilayer sheath material, namely, graphene nanosheets/thin gold film/graphene nanosheets (GNSs/Au/GNSs); and a thin polydimethylsiloxane (PDMS) wrapping layer. The combination of the PU yarn, multilayer GNSs/Au/GNSs, and PDMS wrapping layer enables the strain sensor to achieve high flexibility and stretchability, high sensitivity, broad strain-sensing range, and good waterproof property simultaneously due to the infiltration of PDMS into the multilayer during stretching. Particularly, the yarn strain sensor exhibits a high gauge factor (GF: 661.59), outstanding stability with an applied strain of 50% for approximately 10 000 stretch/release cycles, and superior water resistance. Moreover, it can be readily integrated into textiles, including medical textile bandages and textile gloves, for monitoring various human motions (e.g., phonation, pulse, finger bending, and walking) and effectively control a hand robot. Therefore, strain sensors show considerable potential in textile, wearable, and biomedical electronics for healthcare-related applications, such as disease diagnosis, preventive healthcare, and rehabilitation care, and robot controlling-related applications (e.g., controlling a hand robot to catch some objects).

This paper investigates the effect of driving voltage on the attachment force of an electroadhesion actuator, as the existing literature on the saturation of the adhesive force at a higher electric field is incomplete. A new type of electroadhesion actuator using normally available materials, such as aluminum foil, PVC tape and a silicone rubber sheet used for keyboard protection, has been developed with a simple layered structure that is capable of developing adhesive force consistently. The developed actuator is subjected to the experiment for the evaluation of various test surfaces; aluminum, brick, ceramic, concrete and glass. The driving high voltage is varied in steps to determine the characteristics of the output holding force. Results show a quadratic relation between F (adhesion force) and V (driving voltage) within the 2 kV range. After this range, the F-V responses consistently show a saturation trend at high electric fields. Next, the concept of the leakage current that can occur in the dielectric material and the corona discharge through air has been introduced. Results show that the voltage level, which corresponds to the beginning of the supply current, matches well with the beginning of the force saturation. With the confirmation of this hypothesis, a working model for electroadhesion actuation is proposed. Based on the experimental results, it is proposed that such a kind of actuator can be driven within a range of optimum high voltage to remain electrically efficient. This practice is recommended for the future design, development and characterization of electroadhesion actuators for robotic applications.

Electrostatic Adhesion (ESA) was chosen as the surface attachment mechanism for Wall Climbing Robot (WCR) for its qualitative advantages. ESA model was developed to account for both parallel-plane and fringing static fields. Such Electrostatic Pad model yields equations governing the ESA force and the geometrical conditions for maximum ESA pressure per pad area. This paper shows that the parameters due to applied voltage, and also geometrical properties, material properties and compliance to wall surface of the Electrostatic Pad do affect the ESA force. The simulation also shows that fringing fields may account up to above 10% of total generated ESA force.

Trenchless rehabilitation of underground pipes is increasingly important for city operation. A miniature robotic spraying system is developed to rehab buried pipes by remote spraying plural component protective coating to form lining on the original pipe inner wall. The system demonstrated three novelties, namely the remote mixing and spraying under low pressure, the long-range delivery of viscous coating using low pressure, and the hybrid hose step-down design, that make the system objective feasible. This letter presents the system setup and the remote rotary mixing and spraying mechanism. The mechanism is composed of a mixing chamber and a spray bit assembly. Half of the spray bit assembly with blade mixer feature stays in the mixing chamber for coating mixing, while the other half with rotary atomizer feature stays outside the chamber for spraying. Coatings are fed to the mixing chamber on ratio using low pressure and sprayed out by the high-speed rotation after mixing. The system setup and the mechanism are experimentally validated. The proposed method further opens the possibility of performing remote mixing and spraying over a long distance.