A Computing Method to Determine the Performance of an Ionic Liquid Gel Soft Actuator

Predicting the Bending of 3D Printed Hyperelastic Polymer Components

The advancement of 3D printing has led to its widespread use. NinjaFlex^®, a thermoplastic polyurethane (TPU) filament, is a highly durable and flexible material that has been used to create flexible parts. While this material has been available for nearly two decades, the mechanical properties of 3D printed NinjaFlex^® parts are not well-understood, especially in bending. The focus of this research was predicting the behavior of small 3D printed NinjaFlex^® components. Three-dimensionally printed rectangular specimens of varying lengths and aspect ratios were loaded as cantilevers. The deflection of these specimens was measured using a computer. The experimental results were compared to a modified form of the Euler-Bernoulli Beam Theorem (MEB), which was developed to account for nonlinearities associated with large deflection. Additionally, experimental results were compared to the finite element analysis (FEA). The results showed that both modeling approaches were overall accurate, with the average difference between experimental deflection data and MEB predictions ranging from 0.6% to 3.0%, while the FEA predictions ranged from 0.4% to 2.4%. In the case of the most flexible specimens, MEB underestimated the experimental results, while FEA led to higher retraction.

Multilayer Double-Sided Microstructured Flexible Iontronic Pressure Sensor with a Record-wide Linear Working Range

Wearable electronics, electronic skins, and human-machine interfaces demand flexible sensors with not only high sensitivity but also a wide linear working range. The latter remains a great challenge and has become a big hurdle for some of the key advancements imperative to these fields. Here, we present a flexible capacitive pressure sensor with ultrabroad linear working range and high sensitivity. The dielectric layer of the sensor is composed of multiple layers of double-sided microstructured ionic gel films. The multilayered structure and the gaps between adjacent films with random topography and size enhance the compressibility of the sensor and distribute the stress evenly to each layer, enabling a linear working range from 0.013 to 2063 kPa. Also, the densely distributed protrusive microstructures in the electric double layer contribute to a sensitivity of 9.17 kPa^-1 for the entire linear working range. For the first time, a highly sensitive pressure sensor that can measure loading conditions across 6 orders of magnitude is demonstrated. With the consistent and stable performance from a low- to high-measurement range, the proposed pressure sensor can be used in many applications without the need for recalibration to suit different loading scenarios.

Motion Simulation of Ionic Liquid Gel Soft Actuators Based on CPG Control

The ionic liquid gel (ILG), a new type of soft actuator material, is a mixture of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄), hydroxyethyl methacrylate (HEMA), diethoxyacetophenone (DEAP), and ZrO₂ polymerized into a gel state under ultraviolet (UV) light irradiation. The soft actuator structure consists of a layer of ionic liquid polymer gel sandwiched between two layers of activated carbon capped with gold foil. The volume of the cationic BMIM⁺ in the ionic liquid BMIMBF₄ is much larger than that of the anionic BF₄ ^-. When voltages are applied to both sides of the actuator, the anions and cations move toward the anode and cathode of the electrode, respectively, under the electric field. The volume of the ILG cathode side therefore expands, and the volume of the ILG anode side shrinks, hence bending the entire actuator toward the anode side. The Ogden model was selected as the hyperelastic constitutive model to study the mechanical properties of the ILG by nonlinear analysis. As the ILG is an ideal material for the preparation of a supercapacitor, the equivalent circuit of the ILG can be modeled by the supercapacitor theory to identify the transfer function of the soft actuator. The central pattern generator (CPG) control is widely used in the area of biology, and CPGs based on bioinspired control methods have attracted great attention from researchers worldwide. After the continuum soft actuator is discretized, the CPG-based bioinspired method can be used to control the soft robot drivers. According to the simulation analysis results, the soft actuator can be smooth enough to reach the specified location.