Fig. 2

Morphological and mechanical characterization of the (BY + EGF)@MNs. a The fabricated process diagram of the (BY + EGF)@MNs. b Optical bright-filed and c corresponding fluorescent images of the (BY + EGF)@MNs. d, e SEM images of the MN tips of the (BY + EGF)@MNs at different magnifications. f The mechanical compression test of MN tips. g The force-displacement curves of MN tips with gradient GelMA. h The compression force when the sensor moved 500 μm (n = 4). i The mechanical tensile test of MN bases. j The force-displacement curves of the MN bases with gradient carbomer contents. k The maximum adhesion force between pig skin and MN bases with gradient carbomer contents (n = 3). Scale bars are 500 μm in (b–e)