Co-Design Insights for Mechanically Active Flexible Printed Circuit Boards Through the CurveQuad Origami Robot

Folding flexible printed circuitboards (FPCBs) into origami patterns offers a route to fabricating robots with actuation, sensing, and control fully integrated into the robot body. However, integrating electronics into origami robots introduces a coupled electrical and mechanical design problem since the circuit layout affects the local stiffness and mass distribution and therefore the deformation mechanics. We explore this problem in the context of the FPCB CurveQuad, a centimeter-scale curved-crease origami quadruped. The robot body is fabricated as a folded double-sided FPCB that contains the crease pattern, copper routing, sensors, local stiffening features, and electrical interfaces. A single servomotor drives tendons on the underside of the body, enabling the sheet to self-fold from a planar state and twist for crawling and steering. The resulting robot is 60 mm $\times$ 65 mm $\times$ 50 mm in the folded state and weighs 10.9 g. It crawls at 16.8 mm  $s^{-1}$ (0.259 body lengths $s^{-1}$ ), steers by shifting the actuator oscillation range, and is capable of feedback control. We present our design process for this robot, illustrating strategies for addressing electromechanical co-design with complex bending requirements, enabling folded FPCBs to function as robotic mechanisms rather than simply as passive electronics substrates.