Recently, researchers have concentrated on studying ionic polymer metal composite (IPMC) artificial muscle, which has numerous advantages including a relatively large strain under low input voltage, flexibility, high response, low noise, light weight, and high driving energy density. This paper reports recent developments in IPMC artificial muscle, including improvement methods, modeling, and applications. Different types of IPMCs are described, along with various methods for overcoming some shortcomings, including improvement of Nafion matrix membranes, surface preparation of Nafion membranes, the choice of high-performing electrodes, and new electro-active polymers for enhancing the properties of IPMCs. IPMC models are also reviewed, providing theoretical guidance for studying the performance and applications of IPMCs. Successful applications such as bio-inspired robots, opto-mechatronic systems, and medical engineering are discussed.

In this study, a highly stable air-operating ionic polymer–metal composite (IPMC) actuator with consecutive channels suitable for transportation of the cations and anions of ionic liquids was prepared by introducing and removing copper foam. The electromechanical properties of this novel porous IPMC were investigated. Scanning electron microscopy observation showed that channels and pores ranging in size from ∼100 nm to ∼50 μ m were distributed in the Nafion membrane. The porous IPMC was doped with 1-ethyl-3-methylimidazolium thiocyanate ionic liquid. A larger capacitance (285.00 mF cm ⁻² ) was obtained, which can be attributed to the electric double layer generated at the interface between the ionic polymer membrane and platinum electrode under the input voltage. The fast ion migration channels, high conductivity, and large capacitance enabled high strain of 0.051%–0.666%, a relatively large blocking force of 17.63 mN, and excellent actuation durability for more than 180 000 cycles to be achieved. Furthermore, a soft gripper consisting of a bio-inspired micropillar dry adhesive glued on one surface of the porous IPMC assembled with a mobile mechanical arm was fabricated, and the soft gripper successfully grabbed objects with various features.

Ionic polymer-metal composite (IPMC) is an electro-active polymer material, which has many advantages such as small size, light weight, low driving voltage, large strain, and good biocompatibility. However, the conventional sheet IPMC has the shortcoming of only bending in the two-dimensional plane, which greatly limits the application of IPMC in the field of interventional surgery. In this work, a square rod-shaped IPMC with multi-degree-of-freedom motion was fabricated, and the displacement and blocking force of the square rod-shaped IPMC in different directions are measured and analyzed under the DC voltage signal. An interventional catheter was designed using the square rod-shaped IPMC in order to achieve active guidance, and a simulation experiment platform and a model of human aorta were built to successfully complete the in vitro simulation experiment of interventional surgery, which preliminarily verified the feasibility of the square rod-shaped IPMC in the field of interventional surgery. Graphical abstract

In this work, we printed a Nafion precursor membrane by fused deposition modeling (FDM) rapid prototyping technology and further fabricated IPMCs by electroless plating. The ion-exchange capacity of the Nafion membrane was tested, and the morphology of IPMCs was observed. The electro-mechanical properties of IPMCs under AC voltage inputs were studied, and grasping experiments were performed. The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity. SEM observed that the thickness of the IPMC’s electrode layer was about 400 nm, and the platinum layer was tightly combined with the substrate membrane. When using a square wave input of 3.5 V and 0.1 Hz, the maximum current of IPMCs reached 0.30 A, and the displacement and blocking force were 7.57 mm and 10.5 mN, respectively. The new fabrication process ensures the good driving performance of the printed IPMC. And two pieces of IPMCs can capture the irregular objects successfully, indicating the feasibility of printing IPMCs by FDM technology. This paper provides a new and simple method for the fabrication of three-dimensional IPMCs, which can be further applied in flexible grippers and soft robotics. GRAPHICAL ABSTRACT

Motion capture based on multi-camera is widely used in the quantification of animal locomotor behaviors and this is one of the main research methods to reveal the physical laws of animal locomotion and to inspire the design and realization of bionic robot. It has been found that the multi-camera layout patterns greatly affect the effect of motion capture. Due to the researches for animals of diverse species, determining the most appropriate layout patterns to achieve excellent capture performance remains an unresolved challenge. To improve the capturing accuracy, this investigation focuses on the method of multi-camera layout as a motion capture system for diverse animals with significant differences in outward appearance characteristics and locomotor behaviors. The demand boundaries of motion capture are determined according to the appearance types (shapes and space volume) and the behavior characteristics of the animals, resulting in the matching principle of the typical multi-camera layout patterns (arch, annular and half-annular) with diverse animals. The results of the calibration experiments show that the average standard deviation rate (ASDR) of multi-camera system in the half-annular layout patterns (0.52%) is apparently smaller than that of the other two patterns, while its intersecting volume is the largest among the three patterns. The ASDR at different depths of field in a half-annular layout demonstrate that the greater depth of field is conducive to improving the precision of the motion capture system. Laboratory experiments of the motion capture for small animals (geckos and spiders) employed the multi-camera system locked in the 3-D force measuring platform in a half-annular layout pattern indicate that the ASDR of them could reach less than 3.8% and their capturing deviation rate (ACDR) are respectively 3.43% and 1.74%. In this report, the correlations between the motion capture demand boundaries of small animals and the characteristics of the multi-camera layout patterns were determined to advance the motion capture experimental technology for all kinds of small animals, which can provide effective support for the understanding of animal locomotion.