An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.

Analyte Monitoring Device And Methods Of Use

A number of materials have been explored for their use as artificial muscles Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle-like actuation DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied Materials combining very high energy densities, strains, and efficiencies have been known for some time To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications

Advances in dielectric elastomers for actuators and artificial muscles.

The increasing understanding of the advantages offered by fish and insect-like locomotion is creating a demand for muscle-like materials capable of mimicking nature's mechanisms. Actuator materials that employ voltage, field, light, or temperature driven dimensional changes to produce forces and displacements are suggesting new approaches to propulsion and maneuverability. Fundamental properties of these new materials are presented, and examples of potential undersea applications are examined in order to assist those involved in device design and in actuator research to evaluate the current status and the developing potential of these artificial muscle technologies. Technologies described are based on newly explored materials developed over the past decade, and also on older materials whose properties are not widely known. The materials are dielectric elastomers, ferroelectric polymers, liquid crystal elastomers, thermal and ferroelectric shape memory alloys, ionic polymer/metal composites, conducting polymers, and carbon nanotubes. Relative merits and challenges associated with the artificial muscle technologies are elucidated in two case studies. A summary table provides a quick guide to all technologies that are discussed.

Artificial muscle technology: physical principles and naval prospects

The present invention relates generally to systems and methods for measuring an analyte in a host. More particularly, the present invention relates to systems and methods for transcutaneous measurement of glucose in a host.

Transcutaneous analyte sensor

Polymer artificial muscles

The invention describes rolled electroactive polymer devices. The invention also describes employment of these devices in a wide array of applications and methods for their fabrication. A rolled electroactive polymer device converts between electrical and mechanical energy; and includes a rolled electroactive polymer and at least two electrodes to provide the mechanical/electrical energy conversion. Prestrain is typically applied to the polymer. In one embodiment, a rolled electroactive polymer device employs a mechanism, such as a spring, that provides a force to prestrain the polymer. Since prestrain improves mechanical/electrical energy conversion for many electroactive polymers, the mechanism thus improves performance of the rolled electroactive polymer device.

Rolled electroactive polymers

Described herein are compliant electroactive polymer transducers for use in acoustic applications. A compliant electroactive polymer transducer includes a compliant electroactive polymer at least two electrodes. For sound production, circuitry in electrical communication with the transducer electrodes is configured to apply a driving signal that causes the electroactive polymer to deflect in the acoustic range.

Compliant electroactive polymer transducers for sonic applications

While Electroactive Polymer Artificial Muscle (EPAM) has been presented extensively as a solution for actuation and generation technology, EPAM technology can also be used in multiple novel applications as a discrete or integrated sensor. When an EPAM device, an elastic polymer with compliant electrodes, is mechanically deformed, both the capacitance of the EPAM device, as well as the electrode and dielectric resistance, is changed. The capacitance and resistance of the sensor can be measured using various types of circuitry, some of which are presented in this paper. EPAM sensors offer several potential advantages over traditional sensors including operation over large strain ranges, ease of patterning for distinctive sensing capabilities, flexibility to allow unique integration into components, stable performance over a wide temperature range and low power consumption. Some existing challenges facing the commercialization of EPAM sensors are presented, along with solutions describing how those challenges are likely to be overcome. The paper describes several applications for EPAM sensors, such as an integrated diagnostic tool for industrial equipment and sensors for process and systems monitoring.

Applications of dielectric elastomer EPAM sensors

Electroactive polymers (EAPs) that are suitable for actuators undergo changes in size, shape, or stress state upon the application of an electrical stimulus. Much research in the field of EAPs tends to focus on the development and understanding of the polymer materials themselves. However, practical devices require that changes in dimension and stress state be effectively exploited to produce the desired functionalities (e.g., driving the motion of a robot limb or simply changing appearance or surface texture). This chapter focuses on those issues that must be considered in implementing EAP materials in practical devices.

For purposes of discussion we will focus on one particular type of electroactive polymer: dielectric elastomers. In the literature [e.g., Liu, Bar-Cohen, and Leary, 1999] and elsewhere in this book, dielectric elastomers are also known as electrostatically stricted polymers. Dielectric elastomers are a type of electronic EAPs as defined in Chapter 1 of this book - in that their operation is based on the electromechanical response of polymer materials to the application of an electric field. They have demonstrated good performance over a range of performance parameters and thus show potential for a wide range of applications. Dielectric elastomers were pioneered by SRI International, but several research groups around the world are actively investigating applications of this technology [e.g., Wingert et al., 2002; Sommer-Larsen et al., 2001; Jeon et al., 2001]. While the principle of operation of dielectric elastomer EAPs is not used with all EAPs, many of the issues we will discuss are common to all. These issues include the high compliance and large strains that EAPs can produce, as well as the necessity of simultaneous consideration of both the electrical properties and mechanical properties of materials.

This chapter is organized as follows. First, we consider the specifications used to match actuation technologies with applications, and when it makes sense to consider EAPs. Next, we discuss the basic principles of dielectric elastomer technology. We then consider design issues that may affect the actuation performance of dielectric elastomer EAPs, as well as the operational characteristics of EAPs and how they may affect an application. We present several examples of dielectric elastomer actuators for a wide range of applications, highlighting both the potential advantages of EAPs and the challenges associated with their use. Finally, we conclude with a brief summary of the subchapter and a discussion of the future of EAP application.

Application of Dielectric Elastomer EAP Actuators

Many different actuator configurations based on SRI International’s dielectric elastomer (DE) type of electroactive polymer (EAP) have been developed for a variety of applications. These actuators have shown excellent actuation properties including maximum actuation strains of up to 380% and energy densities of up to 3.4 J/g, using the planar mode of actuation. Recently, SRI has investigated different configurations of DE actuators that allow complex changes in surface shape and thus the creation of active surface texture. In this configuration, the “active” polymer film is bonded or coated with a thicker passive layer, such that changes in the polymer thickness during actuation of the DE device are at least partially transferred to (and often amplified by) the passive layer. Although the device gives out-of-plane motion, it can nonetheless be fabricated using two-dimensional patterning. The result is a rugged, flexible, and conformal skin that can be spatially actuated by subjecting patterned electrodes on a polymer substrate to an electric field. Using thickness-mode DE, we have demonstrated thickness changes of the order of 0.5 - 2 mm by laminating a passive
elastomeric layer to a DE polymer that is only 60 μm in thickness. Such thickness changes would otherwise require a very large number of stacked layers of the DE film to produce comparable surface deformations. Preliminary pressures of 4.2 kPa (0.6 psi) in a direction normal to the plane of the DE film have been measured. However, theoretical calculations indicate that pressures of the order of 100 kPa are feasible using a single layer of DE film. Stacking multiple layers of DE film can lead to a further increase in achievable actuation pressures. Even with current levels of thickness change and actuation pressures, potential applications of such surface texture change are numerous. A thin, compliant pad made from these actuators can have a massaging or sensory augmentation
function, and can be incorporated into garments if desired. The bumps and troughs could act as valves or pumping elements in a fluidic or microfluidic system. Such a device could also be the basis of a smart skin that controls boundary-layer flow properties in a boat or airplane so as to reduce overall drag. The DE elements of the pad can also be used as sensors to make a touch-sensitive skin for recording human interaction with the environment. By driving a thin, compliant vibrating layer at resonant frequencies, one can also configure these devices as solid or fluidic conveyors that transport material on a macroscopic or microscopic scale.

Neville A. Bonwit

Papers

Rolled electroactive polymers

Compliant electroactive polymer transducers for sonic applications

Applications of dielectric elastomer EPAM sensors

Application of Dielectric Elastomer EAP Actuators

Programmable surface deformation: thickness-mode electroactive polymer actuators and their applications