  The Hair clip mechanism (HCM) is an in-plane prestressed bistable mechanism
proposed in our previous research [1]~[5] to enhance the functionality of soft
robotics. HCMs have several advantages, such as high rigidity, high mobility,
good repeatability, and design and fabrication simplicity, compared to existing
soft and compliant robotics. Using our experience with fish robots, this work
delves into designing a novel HCM robotic propulsion system made from PETG
plastic, carbon fiber-reinforced plastic (CFRP), and steel. Detailed derivation
and verification of the HCM theory are given, and the influence of key
parameters like dimensions, material types, and servo motor specifications are
summarized. The designing algorithm offers insight into HCM robotics. It
enables us to search for suitable components, operate robots at a desired
frequency, and achieve high-frequency and high-speed undulatory swimming for
fish robots.
