Robotic Hair with Rich Sensation and Piloerection Functionalities Biomimicked by Stimuli‐Responsive Materials

Abstract

in living organisms, an interesting aspect to mimic would be the accomplishment of complex functionality by the signal flows between the compact and yet demodularized and multifunctional building blocks such as cells, tissues, and organs. A particular challenge in this respect is the highly integrated and compact coupling of sensory and actuation capabilities, [1,2] as in the case of the human hand which is capable of dexterous manipulation relying on its rich sensation, [3] or the mammalian integumentary system that provides not only thermal and tactile sensation, but also the visible and regulatory response of hair erection or collapse on environmental changes. [4] A novel and promising approach along this direction is therefore to construct robots from compact integration of smart, stimuli-responsive materials that exhibit actuation upon external stimulation and, at the same time, further responses such as a resistance change for providing sensation feedback. [5,6] Such an approach relying on "material intelligence" would be in stark contrast with the current mainstream methods for achieving robotic intelligence, which mainly involve modularized functional units such as motors for actuation, and strain or pressure sensors for sensing. [7] Replacing the modularized component approach by the "material intelligence" approach would not only allow devices to be made with smaller sizes, but also enrich the robotic functionality via the intrinsic chemophysical properties of the smart materials. [6,[8][9][10] The recent emergence of new and high-performing smart materials has made it timely to pursue the above "material intelligence" approach, in applications requiring actuation in response to various stimuli including light, humidity, heat, magnetic fields and electricity, [11] as well as sensation by response of resistance, capacitive and optoelectronic signals. [12,13] A few actuation-sensation systems for single stimuli have been made, such as actuators embedded with piezoresistive strain feedback sensing, [14,15] combined sensors and actuators driven solely by moisture [16] or by light, [17] and light-driven actuators with temperature-sensing. [18,19] Integrated multisensing and motility have also been recently demonstrated in systems comprising materials that are thermal and strain sensing, and others that are actuating based on photothermal or shape-memory effects. [20,21] Here, our purpose is to use the material intelligence approach to develop robotic devices that Living organisms are imparted with compact intelligence in which a myriad of functionalities are delivered by highly integrated and demodularized subunits, as in the case of the mammalian skin in which different embedding stimuli-receptors and follicles work together to provide rich sensation for temperature and tactility, as well as the visible and regulatory response of hair erection via the arrector pili muscle. A breakthrough in robotics is to create similar intelligence using emerging stimuli-responsive materials. Here, a thin film composite co...