Electrostatic Adhesion Clutch with Superhigh Force Density Achieved by MXene-Poly(Vinylidene Fluoride–Trifluoroethylene–Chlorotrifluoroethylene) Composites

Abstract

Electrostatic adhesion (EA) clutches are widely applied in robots, wearable devices, and virtual reality, due to their compliance, lightweight, ultrathin profile, and low power consumption. Higher force density has been constantly perpetuated in the past decades since EA was initially proposed. In this study, by composing terpolymer poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] and two-dimensional Ti₃C₂T_<i>x</i> nanosheets (MXene), nanocomposite films with high dielectric constant (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>δ</mml:mi></mml:mrow><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mstyle><mml:mi>'</mml:mi></mml:mstyle></mml:mrow></mml:msubsup></mml:math> > 2300) and low loss tangent are achieved. The force representative index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>δ</mml:mi></mml:mrow><mml:mrow><mml:mi>r</mml:mi></mml:mrow><mml:mrow><mml:mstyle><mml:mi>'</mml:mi></mml:mstyle></mml:mrow></mml:msubsup><mml:msubsup><mml:mrow><mml:mi>E</mml:mi></mml:mrow><mml:mrow><mml:mi>b</mml:mi><mml:mi>d</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msubsup></mml:math> (the relative dielectric constant times the square of breakdown electric field) is enhanced by 5.91 times due to the charge accumulation at matrix-filler interfaces. Superhigh shear stress (85.61 N cm^-2) is generated, 408% higher than the previous maximum value. One of the EA clutches fabricated in this study is only 160 μm thin and 0.4 g heavy. Owing to the low current (<1 μA), the power consumption is <60 mW/cm². It can hold a 2.5 kg weight by only 0.32 cm² area and support an adult (45 kg) (Clinical Trial Registration number: 20210090). With this technology, a dexterous robotic hand is displayed to grasp and release a ball, showing extensive applications of this technique.