Figure 6.

(A) Illustration of the constructed capacitive strain sensor (ⅰ); capacitance variation for detecting finger bending (ⅱ); press cycling experiments of the capacitive strain sensor (ⅲ); the construction of the machine worked with Morse code using the capacitive signals by controlling the pressing time to achieve dots and dashes, and the certain Morse code signal detected by the capacitive strain senso (ⅳ). Reproduced with permission from [97]. (B) Illustration of the cross-section area of the pressure sensors (ⅰ); capacitance changes of the pressure sensor without reliefs and the pressure sensors containing reliefs with different size (ⅱ); monitoring of pressure induced by slight blowing (ⅲ). Reproduced with permission from [98]. (C) Illustration of an array constructed with the PAM/NaCl hydrogels (ⅰ); a picture of the sensor array (ⅱ) and its practical application used for the location detecting (ⅲ). Reproduced with permission from [55].