Fig. 2. Characterization of tactile and olfactory sensing array.

a The design of the array architecture (i) shows the location of the 14 force sensors on each fingertip (ii), along with the location of the six gas sensors on the palm (iii). The Si-based force (iv) and gas (v) sensors are fabricated using microelectromechanical systems techniques and integrated on flexible printed circuits. Blue area: force-sensitive area (single-crystalline silicon beam) with scale bar of 200 μm. Red area: area modified by gas-sensitive material with scale bar of 400 μm. b The sensitivity of the force and gas sensors. n = 12 for each group. The error bars denote standard deviations of the mean. Top: the output voltage response of the force sensor under gradient pressure loading. Bottom: The normalized resistance response of the gas sensor in the continuously increasing ethanol gas concentration. c In a typical touching process, the fingers increasingly get closer to the object until the point of contact (i. reach phase) and experiences a sudden rise in tactile forces as the object is touched (ii. load phase). Then the hand would hold the object for a certain time (iii. hold phase) and at last release the object (iv. release phase). d Response curve of the force sensor during the process of contacting three different objects. When the same force is applied to the objects by the mechanical hand, the deformation degree of the objects varies according to their different elasticity modulus, changing the local contact area and consequent reactive pressure. e The normalized resistance response curve of the gas sensor during the process of contact and separation from the detected gas flow. f Photograph of the mechanical hand touching a human arm, scale bar: 2 cm. g The tactile mappings at three different feature points in (c). Each contains 70 pixels with 14 pixels for each fingertip. h The hexagonal olfactory mappings of three different objects including an arm, worn clothes, and an orange.