Papers by Author: Federico Carpi

Abstract: The need for high electric fields to drive dielectric elastomers is still retaining their diffusion as actuators in some areas of potential application, as in the case of biomedical disciplines. The development of new materials offering superior electromechanical properties is thus an essential requirement in order to effectively reduce the driving fields. In this light, the present work is aimed to enhance the electromechanical properties of two silicone and polyurethane based dielectric elastomers, both by making particulate composites with high-permittivity ceramic fillers, and by blending with a highly polarisable polymeric phase. Due to a consequent worsening of the mechanical properties, pure composite architectures yielded only limited results on the overall electromechanical response. With the blend approach, instead, both an increase of the dielectric permittivity and an unexpected reduction of the tensile elastic modulus were observed, leading to an overall increase of the electromechanical response. In any case, a key role appears to be played by the nature and intensity of polarisation phenomena arising at interfaces between different phases.

Abstract: Technologies for space applications are often considered to be rather conservative, aimed at ensuring reliability and robustness. Nevertheless, novel concepts coming from research activities have been and are always the lymph for the development of successful and competitive new solutions. This paper presents new concepts and ideas inspired by natural systems with distributed actuation embedded in their structure, considered as ideal models for possible uses in space applications. Preliminary concepts for possible technical solutions for long-term future implementations are here proposed and briefly analyzed. Peristaltic-like actuations obtained by the use of dielectric elastomer actuators is proposed as one of the most promising solutions. Experimental performances of a single actuation unit are here presented and directions for future implementations are proposed.

Abstract: Dielectric elastomer (DE) actuators are able to typically show significant electromechanical performances, which make this electroactive polymer technology particularly attractive for so-called ‘artificial muscle’ devices. This paper deals with two types of DE actuators recently developed in our lab. The first type is represented by the so-called ‘folded actuators’, based on a simple configuration suitable to easily implement linear contractile devices. The structure consists of a monolithic electroded sheet of elastomer, which is folded up and compacted; the resulting contractile actuator is functionally equivalent to a multilayer stack with interdigitated electrodes, but can be manufactured more easily. The second type of devices is represented by the so-called ‘buckling actuators’. They operate with out-of-plane unidirectional displacements of an elastomer membrane. This paper describes the structure and the properties of both these actuators, along with different examples of applications currently being developed in our lab for the biomedical, the robotic and the space fields.

Abstract: This paper describes the early conception and latest developments of electroactive polymer (EAP)- based sensors, actuators and power sources, implemented as wearable devices for smart electronic textiles (e-textiles). Such textiles, functioning as multifunctional wearable human interfaces, are today considered relevant promoters of progress and useful tools in several biomedical field, such as biomonitoring, rehabilitation and telemedicine. This paper presents the more performing EAPbased devices developed by our lab and other research groups for sensing, actuating and energy harvesting, with reference to their already demonstrated or potential applicability to electronic textiles.

Abstract: We present a new concept for compact, tunable antennas. Traditional approaches have circuits and switchable elements which can be bulky and lossy. Here we investigate structures which offer direct tuning through voltage-controlled deformation of the radiating structure itself. The antenna is a dielectric resonator (DRA), where the antenna impedance and tuning depends on the shape of the dielectric. The deformation action is through using electro-active polymer (EAP) for the dielectric. EAPs have promising properties for smart antennas and ongoing developments are continuing to improve its suitability.