Flexible printed circuit boards (FPCB) are widely used in smart devices with high wiring density and light weight. In this paper, the chemical etching process of FPCB with 18 μm line pitch is investigated. A geometric model of the FPCB circuit with the shape of "T" is established and simulated by the finite element method. The time evolution of the etching cavity, concentration field and velocity field of CuCl2 solution are studied, as well as the effects of initial concentrations and inlet velocities on the etching cavity profile. Finally, the FPCB sample with 18 μm line pitch is successfully fabricated by employing process parameters from the etching simulation. The results show that as the increase in the etching cavity, recirculating eddies form at the bottom of the photoresist in the corners of the etching cavity, resulting in more etching on the top sides of sidewalls over time. Higher initial concentration of the etching solution will result in a larger etching cavity profile, but the inlet velocity cannot affect the etching cavity profile significantly. Finally, the effectiveness of the simulation model is verified by comparing the etching cavity profiles with four experiments. INDEX TERMS FPCB, chemical etching, transport of diluted species

State-of-the-art autonomous micro-robotic turtles suffer from various limitations, such as power restrictions that minimize their deployment times. In this paper, an Ionic Polymer Metal Composite (IPMC) actuator-based centimeter-level biomimetic underwater robot was designed and developed as a robotic turtle with self-charging capabilities to overcome such limitations. It could move forward and make turns driven by five IPMCs on the water. The underwater charging station was able to transmit wideband ultrasonic and electromagnetic fields for electromagnetic induction charging. An ultrasonic communication system with one ultrasonic transmitter and two ultrasonic receivers was first fabricated to implement communication between the underwater station and the biomimetic underwater robot for autonomous tracking and rechargeable capabilities. Experiments were carried out to confirm the operation of the biomimetic underwater robot, which verified the centimeter-level rechargeable capabilities and autonomous target tracking features. The micro-robot demonstrated a self-tracking radial displacement error of approximately 6 mm and a charging reliability rate of more than 73%.

An ionic polymer–metal composite (IPMC) is a kind of soft material. The applications of IPMC in actuators, environmental sensing, and energy harvesting are currently increasing rapidly. In this study, an ordered Nafion nanofibre mat prepared by electrospinning was used to investigate the characteristics of the mechanoelectrical transduction of IPMC. The morphologies of the Nafion nanofibre mat were characterized. The proton conductivity, ion exchange capacities, and water uptake potential of the Nafion nanofibre mat were compared to traditional IPMC, respectively. A novel mechanism of Nafion nanofibre IPMC was designed and the open circuit voltage and short circuit current were measured. The maximum voltage value reached 100 mv. The output power was 3.63 nw and the power density was up to 42.4 μW/Kg under the load resistance. The Nafion nanofibre mat demonstrates excellent mechanoelectrcical transduction behavior compared to traditional IPMC and could be used for the development of self-powered devices in the future.

During the last decades, the ionic polymer-metal composite (IPMC) received much attention because of its potential capabilities, such as large displacement and flexible bending actuation. In this paper, a biomimetic flapping air vehicle was proposed by combining the superiority of ionic polymer metal composite with the bionic beetle flapping principle. The blocking force was compared between casted IPMC and IPMC. The flapping state of the wing was investigated and the maximum displacement and flapping angle were measured. The flapping displacement under different voltage and frequency was tested. The flapping displacement of the wing and the support reaction force were measured under different frequency by experiments. The experimental results indicate that the high voltage and low frequency would get large flapping displacement.

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