Magnetization‐Induced Self‐Assembling of Bendable Microneedle Arrays for Triboelectric Nanogenerators

Abstract Since the invention of triboelectric nanogenerator (TENG) in 2012, it has become one of the most important innovations in energy conversion technologies. A flexible microneedle array (MA)‐based TENG is proposed using the closed bending–friction–deformation behavior of MA for the mechanical energy harvest. A novel magnetization‐induced self‐assembling method is introduced to efficiently fabricate the bendable MA for the TENG. The 3D structures of MA are continuously self‐assembled from a moving film of curable magnetorheological fluid under the assistance of a rotating external magnetic field. The mass production of MA may be achieved using this method in a roll to roll manufacturing mode. A polyethylene film, MA coated with Cr/Au film, and polyethylene film coated with Al film are heat‐sealed from top to bottom as a MA‐based TENG. Under an applied force of 26 N with a frequency of 1.5 Hz, the MA‐based TENG generates an open‐circuit voltage of up to 9 V and a short‐circuit current of up to 12 µA, corresponding to the peak current density of ≈1.37 µA cm⁻². The MA‐based TENG is integrated in an insole of right shoe as an accurate pedometer, which exhibites an excellent energy harvest ability.