Fig. 4: Stretchable sensor networks for pressure mapping and touch recognition.

Schematic diagram (upper) and top views of 2D mapping for output voltage intensity (bottom) response to different applied pressure exerted using different sizes of contact letters “N”, “C”, “H”, and “U” of the surface of 4 × 4 pixelated UTE-skin (a) without and (b) with a top shielding layer. c Photograph of a large-area matrix of 4 × 4 pixelated UTE-skin without a shielding layer (25 × 25 cm²). d Schematic of sliding mode and (e) output voltages of pixels in the moving trajectory of the finger writing the letter “N” on the surface of UTE-skin without a shielding layer. f Photograph of a 4 × 4 pixelated UTE-skin with a shielding layer (25 × 25 cm²). g Schematic of sliding mode and (h) output voltages of pixels in the moving trajectory of the finger writing the letter “N” on the surface of UTE-skin with a shielding layer. The term (a.u.) in (e, h) represents the arbitrary unit. i Schematic diagram of the electrical signal tests of UTE-skin with two adjacent sensing panels spaced d apart. j Output voltage signals of the two adjacent sensing nodes with different electrode spacing by touching the left one. For a fair comparison, the tapping sites highlighted at the left panel were operated with a uniform contact pressure and area. k Plots of the statistical anti-interference index of UTE-skin sensory system relying on different spacings from j, displaying the anti-interference abilities of tactile sensors at each spacing to improve the system-level design. Note that the index was extracted from the ratio of (V₀ − V)/V₀, where V and V₀ were the measured voltage values for each cell with possible disturbance and without disturbance, respectively. A curved arrow was utilized to guide the eyes.