In this paper, we propose a piezoelectric actuator-sensor pair that can classify several objects. It consists of two polyvinylidene-fluoride films above a polyethylene-terephthalate substrate. Herein, the actuator is connected to an voltage supplier, and the sensor output signal is acquired through a measuring equipment. Specifically, this pair is installed on a robot hand. When the objects are grasped by the robot hand in static state, the actuator oscillates as sinusoidal input voltages with frequency sweep are applied for a few seconds. At the same time, the sensor data is obtained and undergoes preprocessing procedure for learning process. The neural network classifier model is trained by learning process. After conducting the learning process, we test the feasibility of the actuator-sensor pair by demonstrating the real-time recognition system.
Piezoelectric materials have found numerous applications in sensors with the characteristic of flexibility and sensitivity. Taking advantage of their characteristic, we fabricate a multi-layered cross-shaped piezoelectric sensor for torsional load analysis. It consists of a polyethylene terephthalate substrate and two piezoelectric layers placed in the crossed form. From the crossed shape of two piezoelectrics, various conditions of torsional loading can be analyzed by simply measuring load voltage amplitudes and phases. We derive a modeling framework of the cross-shaped piezoelectric sensor under torsional loading to expect the sensing response of the sensors. Also, an experimental setup is established to verify the modeling statement.
Materials engineering has greatly contributed to improving the performance of soft active materials, but these improvements have seldom met the compelling needs of science and engineering applications. Here, we demonstrate, for the first time, a new approach to the design of soft active materials, which embraces the complexity of multiphysics phenomena across electrostatics and electrochemistry. Through principled experiments and physically-based models we investigate the integration of electrostatic actuation in ionic polymer-metal composites (IPMCs).
In human hand, there are numerous energy sources such as finger bending and grasping. In previous studies, most energy harvesters have been attached to joints. Herein, we use another energy source during finger bending motion. Specifically, we focus on the shape change of the finger from bending and propose a ring shaped piezoelectric energy harvester. It consists of an anterior piezoelectric ring and an exterior silicone ring. We utilize a silicone cylinder to mimic the finger shape change situation. We measure and observe electrical responses from the piezoelectric energy harvester for the finger shape change.
In this paper, we propose a soft robotic gripper to be mounted easily and to have high actuation force by harnessing electrostatic and hydraulic phenomena. Specifically, we develop a soft actuator to consist of swelling pouches, a silicon backbone beam, and a supplying pouch with electrodes on its both surfaces. The two pouches include dielectric fluid, and they are connected. When a high voltage is applied to the electrode of the supplying pouch, the fluid in the pouch moves to the swelling one. In addition, we present a soft gripper using the soft electro-hydraulic actuators.
The phenomenon of back-relaxation in ionic polymer-metal composites (IPMCs) has attracted the interest of the scientific community for two decades, yet a conclusive explanation of why and when it occurs is presently lacking. Recent studies have suggested that the interplay between osmotic pressure and Maxwell stress could be the key mechanism underlying back-relaxation, but experimental proof is missing to substantiate this hypothesis. Here, we seek to bring forward new evidence from the technical literature in favor of this explanation by analyzing existing experiments on contactless actuation of ionomer strips in an electrolyte solution. We demonstrate that Maxwell stress dominates osmotic pressure in the contactless actuation of ionomers, thereby supporting the claim that Maxwell stress could help understand back-relaxation in IPMCs.
In this paper, we investigate the feasibility of energy harvesting from the torsions using a piezoelectric beam. The piezoelectric beam is partially patterned and is tested in an experimental setup to force pure torsional deformation. In particular, the beam consists of two identical piezoelectric parts attached on one side of a supporting substrate. We propose a model for the energy harvesting system through the equations for a slender composite beam with the physical properties and the electromechanical coupling equations of the piezoelectric material. The theoretical predictions are validated by the comparison with the experimental results.
Ionic Polymer Metal Composites (IPMCs) are electro-responsive materials for sensing and actuation, consisting of an ion-exchange polymeric membrane with ionized units, plated within noble metal electrodes. In this work, we investigate the sensing response of IPMCs that are subject to a through-the-thickness compression, by specializing the continuum model introduced by Cha and Porfiri,1 to this one-dimensional problem. This model modifies the classical Poisson-Nernst-Plank system governing the electrochemistry in the absence of mechanical effects, by accounting for finite deformations underlying the actuation and sensing processes. With the aim of accurately describing the IPMC dynamic compressive behavior, we introduce a spatial asymmetry in the properties of the membrane, which must be accounted for to trigger a sensing response. Then, we determine an analytical solution by applying the singular perturbation theory, and in particular the method of matched asymptotic expansions. This solution shows a good agreement with experimental findings reported in literature.
In this paper, we investigate the feasibility of energy harvesting from the mouse click motion using a piezoelectric
energy transducer. Specifically, we use a robotic finger to realize repeatable mouse click motion. The robotic
finger wears a glove with a pocket for including the piezoelectric material as an energy transducer. We propose
a model for the energy harvesting system through the inverse kinematic framework of parallel joints in the
finger and the electromechanical coupling equations of the piezoelectric material. Experiments are performed to
elucidate the effect of the load resistance and the mouse click motion on energy harvesting.
In this paper, we investigate the feasibility of energy harvesting from axisymmetric vibrations of annular ionic polymer metal composites (IPMCs). We consider an in-house fabricated IPMC that is clamped at its inner radius to a moving base and is free at its outer radius. We propose a physics-based model for energy harvesting from underwater vibrations, in which the IPMC is described as a thin annular plate undergoing axisymmetric vibrations with an added mass due to the encompassing fluid. Experiments are performed to elucidate the effect of the shunting resistance and the excitation frequency on energy harvesting.
In this paper, we propose a novel modeling framework to study quasi-static large deformations and electrochemistry of ionic polymer metal composites (IPMCs). The chemoelectromechanical constitutive behavior is obtained from a Helmholtz free energy density, which accounts for mechanical stretching, ion mixing, and electric polarization. The framework is specialized to plane bending of thin IPMCs through a structural model, where the bending moment of the IPMC is computed from a one-dimensional modified Poisson-Nernst-Planck system. For small static deformations, we establish a semianalytical solution based on the method of matched asymptotic expansions, which we ultimately use to elucidate the physics of IPMC sensing and actuation.
In this paper, we study the charge dynamics of ionic polymer metal composites (IPMCs) in response to an
imposed time-varying flexural deformation. IPMC chemoelectromechanical behavior is described through the
Poisson-Nernst-Planck framework, and the method of matched asymptotic expansions is utilized to establish a
closed-form solution for the electric potential and counterion concentration in the IPMC. This solution is, in
turn, leveraged to derive a mathematically tractable distributed circuit model of IPMC sensing.
This study seeks to investigate the feasibility of energy harvesting from mechanical buckling of ionic polymer metal composites (IPMCs) induced by a steady ﬂuid ﬂow. In particular, we propose a harvesting device composed of a paddle wheel, a slider-crank mechanism, and two IPMCs clamped at both their ends. We test the system in a water tunnel to estimate the eﬀects of the ﬂow speed and the shunting resistance on power harvesting. The classical post-buckling theory of inextensible rods is utilized, in conjunction with a black-box model for IPMC sensing, to interpret experimental results.
In this paper, we analyze buckling of an ionic polymer metal composite (IPMC) shell subjected to uniaxial
compression. A new technique is developed to fabricate tubular IPMCs using hot molding and a chemical
reduction process. The short-circuit current and the mechanical deformation of the sample are recorded during
the compression test. Experimental findings demonstrate that IPMC buckling can be accurately sensed via the
short-circuit current, which is approximately zero during the loading phase, before exhibiting a sudden increase
at the onset of the elastic instability.
In this paper, we analyze the charge dynamics of ionic polymer metal composites (IPMCs) in response to voltage inputs composed of a DC bias and a small AC voltage. IPMC chemoelectrical behavior is described through the Poisson-Nernst-Planck framework. The physics of charge build up and mass transfer at the electrodes are modeled through metal particle layers. Perturbation methods are used to establish an equivalent circuit model for the IPMC electrical response. The proposed approach is validated through comparison with finite element results.