Target shape matching of a 1D lithium-ion battery actuator array

Large volume change in Si anodes can be harnessed to produce lithium-ion (Li-ion) pouch cells that change shape when charged and discharged. In this paper, complex, tailorable three-dimensional shapes are modeled with multiple 1D Li-ion battery (LIB) actuators connected in parallel by a compliant membrane-like material. A shape matching, design optimization is conducted to match these multimorph actuators against complex three-dimensional target shapes. Three-dimensional shapes in LIBs might readily be used for mobile soft robot applications such as minimally invasive surgical tooltips, shape-morphing structural batteries, and active custom rehabilitative aids. This paper models the compliant, membrane-like material as springs that align and transmit force between the actuators. Three case studies are presented that optimize membrane interactions in multi-member actuators. Important results include the successful shape matching of a multi-member, bimorph actuator optimized to shape match a complex 3D shape with less than three percent error. In bimorph multi-actuators, shape error is reduced by enforcing design variable symmetry and implementing different state of charge (SOC) to further reduce the number of design variables. Thus, for design optimization of multi-actuator batteries, enforcement of symmetry is recommended with design variables to include both differential SOC (or equivalent actuation strain parameter) and active layer coating thickness to achieve complex, tailorable shapes with a LIB actuator array. Differential SOC is further discovered to allow for the decoupling of bending and SOC allowing for more tailorable battery actuator applications.