Robotic hand exoskeletons can provide assistance to people who suffer from hand functional disability or spinal cord injury (SCI). However, the current hand exoskeletons remain challenging with respect to having a user-friendly design that satisfies human motion with a lightweight structure. Here we propose a method of using topology optimization in the design of finger exoskeletons, which is a lightweight and integrate manufactured exoskeleton. The exoskeleton is designed by generating the topology configuration according to the bending state of the finger. The objective function in the optimization is set to be the maximization of output displacement of the design domain. After obtaining the topology configuration, a conjugate surface flexure hinge is developed as an elastic joint to replace the compliant part of the topologies. Finally, a rigid-compliant parallel exoskeleton is fabricated by a 3D printer and the performance of the mechanism is verified.