Ionic Polymer Metal Composites (IPMCs) have several unique characteristics such as, low driving voltage, no
moving parts, etc., that allow the material to fulfill specific needs for medical device applications. However, there are
numerous challenges that must be addressed in order to utilize IPMC in medical devices. The research presented is a
culmination of efforts that address a number of these issues; such as electrolysis of water, safety concerns, material
characterization and in vitro testing. Work on IPMC development has raised the threshold of the electrolysis of water
during actuation from 2.35 V to 2.46 V in Tyrode's solution. The problem of back relaxation under DC excitation has
been reduced. To ensure accurate measurements of IPMC performance, for medical applications, it is imperative that the
appropriate in vitro testing conditions are chosen, such details are discussed. Material characterization techniques
developed and used by Pavad Medical, which are based on medical device needs, are also highlighted.
In this paper, we present the development of an empirical force model and the feedback control of the force produced by Ionic Polymer Metal Composite (IPMC). IPMC shows great potential as a low-mass, high-displacement actuator. The high-precision force generation capability of IPMC at low force level makes it ideal for the microdevice applications such as microgrippers. Thus, modeling of the force generated by IPMC is of critical importance along with its control. Force models previously developed are based on the electrochemical and electromechanical phenomena. Most of these models consisted of partial differential equations representing each phenomenon, so it is difficult to develop a force controller on the basis of these models. This paper presents a force model developed for an IPMC strip by system identification and the feedback control of the force produced by the IPMC strip. After the implementation of the controller, the settling time is reduced to 1.5 s from 10 s in open loop, and the overshoot is reduced to 30% from 125% in open loop. The crossover frequency is 1.3 Hz limited by the structural resonance of the polymer strip.
This paper presents the experimental method to evaluate the adhesion forces between micro-objects and IPMC, and describes methods to reduce them. Ionic Polymer Metal Composite (IPMC) can be a key material in low-mass, high-displacement, single-moving part actuators and shows great potential for micro-gripper applications. To design fingers for a micro-gripper using IPMC, the study of the adhesion force between IPMC and micro-objects is of critical importance. Glass micro-spheres of various sizes were attached to silicon nitride Atomic Force Microscope (AFM) tips, and the adhesion forces between the micro-spheres and the IPMC sample surface were found experimentally by an AFM. These experiments were performed in dry environment. Experiments were then performed under water to see the effect on reduction of adhesion forces. It was found that for a glass micro-sphere of size 32.43-μm the adhesion force decreases from 144 nN in air to 8.64 nN in water.