Artificial multimodal receptors based on ion relaxation dynamics

Feeling temperature and touch The range of receptors in our skin make it possible to sense when we are touching an object and also gives us a general sense of the temperature of that object. Achieving this in an artificial skin-like material has been a challenge because most of the approaches for sensing touch are themselves temperature sensitive. You et al. studied the ion relaxation dynamics in a conductive elastomeric film (see the Perspective by Liu). They show that the ion relaxation time can be used as a strain-insensitive intrinsic variable for detecting temperature and the capacitance can be used as a temperature-insensitive extrinsic variable for sensing the strain, thus decoupling the two so that their signals do not interfere with each other. Science, this issue p. 961; see also p. 910 Real-time acquisition of ion relaxation time enables sensing of strain and temperature in stretchable artificial receptors. Human skin has different types of tactile receptors that can distinguish various mechanical stimuli from temperature. We present a deformable artificial multimodal ionic receptor that can differentiate thermal and mechanical information without signal interference. Two variables are derived from the analysis of the ion relaxation dynamics: the charge relaxation time as a strain-insensitive intrinsic variable to measure absolute temperature and the normalized capacitance as a temperature-insensitive extrinsic variable to measure strain. The artificial receptor with a simple electrode-electrolyte-electrode structure simultaneously detects temperature and strain by measuring the variables at only two measurement frequencies. The human skin–like multimodal receptor array, called multimodal ion-electronic skin (IEM-skin), provides real-time force directions and strain profiles in various tactile motions (shear, pinch, spread, torsion, and so on).