A Biomimetic Interface with High Adhesion, Tailorable Modulus for On-Skin Sensors, and Low-Power Actuators

Recently, stimuli-responsive sensors and actuators have drawn significant attention as they are promising in a wide scope of applications, including wearable devices and soft robotics. However, they both face serious challenges in terms of interface management, that is, the weak sensor-skin interfacial interaction and the single binding function in actuators. Herein, we design an adhesive and modulus tailorable interface by in situ polymerization of dopamine (DA) along the poly(vinyl alcohol) (PVA) macromolecular chains and the incorporation of ionic coordination between polymer molecular chains (PVA and polydopamine (PDA) chains) and metal ions (Fe3+). Note that the introduction of hygroscopic Fe3+ cations not only facilitates the coordination to increase the water tolerance of the interface but also improves the water uptake into the system, which is essential for tailoring both the adhesion and modulus of the interface. By adopting this interface, we successfully fabricate a soft (skin-like modulus 0.1-10.0 MPa), ultrathin (similar to 50 mu m), self-adhesive, and skin-compliant sensor. Furthermore, the interface is also applied to bind two active layers to fabricate a multiresponsive (heat, near-infrared (NIR) light, voltage, and humidity) actuator. In addition to the adhesion function, the interface can also help lock the actuator states thanks to the tunable modulus of the interface, which is highly valuable for decreasing the power consumption of the actuator. This work provides a new avenue to address both sensing and actuating bottlenecks by focusing on the interface.