Paola Brunetto

A Tactile Sensor for Biomedical Applications Based on IPMCs

In this paper, a first prototype of a multifunctional tactile sensor using ionic polymer metal composites (IPMCs) is proposed, designed, and tested. Two IPMC strips are used, one as an actuator and one as a sensor, both positioned in a cantilever configuration; working together they enable the system to detect the presence of a material in contact with it and to measure its stiffness. These sensing capabilities can be exploited in various biomedical applications, such as catheterism, laparoscopy and the surgical resection of tumors. Moreover, the simple structure of the proposed tactile sensor can easily be extended to devices in which a sensing tip for exploration of the surrounding environment is required. Compared with other similar tools, the one proposed works with a very low-power supply (the order of magnitude being a few volts), it needs very simple electronics, it is very lightweight and has a low cost.

A model of ionic polymer-metal composite actuators in underwater operations

Ionic polymer metal composites (IPMCs) are active materials that exhibit a bi-directional electromechanical coupling: a voltage produces membrane bending, while by bending an IPMC membrane a voltage output is obtained. IPMCs are of increasing interest in a number of application fields. More specifically, IPMCs can work in wet environments, even in water, and this represents a valuable capability in a number of applications fields such as underwater robotics, surveillance, and biomedical applications. In this work a totally new model of an active IPMC beam, solicited by a voltage signal and immersed in water, is introduced. The model estimates the moment produced by the applied voltage. Therefore, the classical Euler–Bernoulli cantilever beam theory and the concept of hydrodynamic function are used to describe the interaction between the beam and the water. Knowledge of this interaction allows estimation of the IPMC active beam motion in water.

Static and Dynamic Characterization of the Temperature and Humidity Influence on IPMC Actuators

Several models that describe the behavior of ionic polymer-metal composite (IPMC)-based actuators can be found in the literature. The response of IPMC transducers as a function of modifying quantities is a matter of interest; however, it has not been investigated. It is reasonable to argue that environmental humidity and temperature represent the main modifying parameters. In fact, humidity changes the behavior of IPMC transducers, working as both sensors and actuators, because it changes the Young modulus of the devices and, hence, their mechanical response. The influence of temperature is suspected, because polymer characteristics are often influenced by this quantity. In a previous paper, the authors proposed a dynamic model and investigated the scaling effect of geometrical parameters, giving evidence of the excellent agreement between estimations that were obtained using the proposed model and corresponding observations. In this paper, the response of IPMC actuators to both temperature and relative humidity is analyzed, giving interesting information that both integrates IPMC models and allows for a better exploitation of IPMCs.

A resonant vibrating tactile probe for biomedical applications based on IPMC

In this paper preliminary results regarding a vibrating tactile sensor are presented. More specifically, two IPMC strips are used, one as actuator and one as sensor, that work together for the differentiation of tissues. In fact, the characteristics of the resonant vibrating IPMC system change with the applied load. This allows for calculating the parameters of the mechanical load, by measuring the IPMC sensor output signal. The sensing capabilities can be exploited in various biomedical applications, such as catheterism and surgical resection of tumors. The model and the preliminary experimental tests of the proposed probe are reported in the paper.

Characterization of the Temperature and Humidity Influence on Ionic Polymer–Metal Composites as Sensors

In this paper, the characterization of ionic polymer-metal composite (IPMC)-based sensors, for possible applications related to biological systems, with respect to the influence of environmental temperature and relative humidity is investigated. This paper is second in a row devoted to the characterization of IPMC transducers with respect to the aforementioned influencing quantities. The characterization is performed by statistically investigating sensing signals in typical working conditions, and the experiments performed show that, for the investigated ranges, the effects of relative humidity are much more evident than the corresponding effects produced by temperature changes. The results reported give information that integrated IPMC transducer models, which are introduced so far, contribute to better exploit this novel technology.

Electromechanical model for a self-sensing ionic polymer–metal composite actuating device with patterned surface electrodes

This paper further discusses a concept of creating a self-sensing ionic polymer–metal composite (IPMC) actuating device with patterned surface electrodes where the actuator and sensor elements are separated by a grounded shielding electrode. Different patterning methods are discussed and compared in detail; the presented experimental data give an understanding of the qualitative properties of the patterns created. Finally, an electromechanical model of the device is proposed and validated.

Tridimensional ionic polymer metal composites: optimization of the manufacturing techniques

Ionic polymer metal composites (IPMCs) belong to electroactive polymers (EAPs) and have been suggested for various applications due to their light weight and to the fact that they react mechanically when stimulated by an electrical signal and vice versa. Thick IPMCs (3D-IPMCs) have been fabricated by hot pressing several Nafion® 117 films. Additional post-processes (more cycles of Pt electroless plating and dispersing agents) have been applied to improve the 3D-IPMC performance. The electromechanical response of 3D-IPMCs has been examined by applying electrical signals and measuring the displacement and blocking force produced.

A small scale viscometer based on an IPMC actuator and an IPMC sensor

The vibrational characteristics of a cantilever beam strongly depend on the fluid in which the beam is immersed. In this paper, this property is exploited to show the possibility to realize a small scale viscometer based on Electro-Active Polymers. More specifically, two IPMCs (Ionic Polymer Metal Composites) strips, one as actuator and one as sensor are adopted; the IPMC actuator is used to impose a vibration to the whole system, the IPMC sensor is used to measure the amplitude and the frequency of the deflection. A model of the device is presented along with its experimental validation on sucrose solutions.

A small scale viscometer based on IPMCs

Abstract Abstract The vibrational characteristics of a cantilever beam are well known to depend strongly on the fluid in which the beam is immersed. In this paper, we exploit this property to obtain a small scale viscometer, by using an IPMC (Ionic Polymer Metal Composites) based beam. IPMCs are polymeric composites with a lot of interesting properties: they are light, flexible, low cost and biocompatible and present an interesting electro-mechanical coupling capability, moreover by using IPMC it would be possible to obtain integrated devices, being the conditioning circuitry very simple. In this paper a model of the device is presented along with its experimental validation.

Experiments with self-sensing IPMC actuating device

This paper presents a realization of a self-sensing ionic polymer-metal composite (IPMC) device by patterning its surface electrodes and thus creating separate actuator and sensor parts. The sensor and actuator elements of such device are still electrically coupled through the capacitance and/or conductivity of the ionic polymer. By creating a separate grounded shielding electrode between the two parts, it is possible to suppress significantly the undesired cross-talk from the actuator to the sensor. The paper at hand compares three different methods for separating sensor and actuator parts: manual scraping, machine milling, and laser ablation. The basis of comparison of the methods is the electrical characteristics of the device after realizing the surface patterns and the convenience of manufacturing.