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Molecular-level self-assembly processes allow the formation of novel materials with properties that are not achievable using conventional fabrication methods. For example, nanostructured metals and polymers may be combined to form inorganic/organic materials that exhibit properties typically associated with each of these species separately, namely high electrical conductivity and low Young's modulus. The combination of such properties is of interest for a number of engineering applications. For example, methods to form stretchable metal conductors, either on elastomeric substrates or as free-standing materials, have been investigated for some time, in part as a way to overcome the high modulus of sensor and actuator electrode materials, and more generally to address the need for mechanically flexible interconnections in polymer electronic devices, flex circuits, electronic textiles and similar electrical circuit applications. Of particular recent interest for example is summarized in [1] where a process to form electrical connectivity using 100 nm-wide gold stripes evaporated onto polydimethylsiloxane (PDMS) is reported, and where non-zero electrical conductivity was observed for strains up to 22%.

We report recent improvements of Metal RubberTM strain sensors formed by electrostatic self-assembly (ESA) processing. The sensors may be used to measure strains from approximately 1 microstrain to several hundred percent strain, over gauge lengths ranging from approximately 1 millimeter to several tens of centimeters.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper describes the use of Metal Rubber, which is an electrically conductive, low modulus, and optically transparent free-standing nanocomposite, as an electrode for active polymer devices. With its controllable and tailorable properties [such as modulus (from ~ 1 MPa to 100 MPa), electrical conductivity, sensitivity to flex and strain, thickness, transmission, glass transition, and more], Metal Rubber exhibits massive improvements over traditional stiff electrodes that physically constrain the actuator device motion and thus limit productivity. Metal Rubber shows exceptional potential for use as flexible electrodes for many active polymer applications.

This paper describes the commercial applications of Metal Rubber, the first material of its kind, a self-assembled free-standing electrically conductive elastomer in biomedical, aerospace and microelectronic areas. Metal Rubber is a novel nanocomposite formed via the self-assembly processing of metal nanoparticles and elastomeric polyectrolytes. This type of processing allows for control over bulk mechanical and electrical properties and requires only ppm quantities of metal to achieve percolation. The use of nanostructured precursors also results in transparent, electrically conductive nanocomposites. Metal Rubber elastomers are being developed as electrodes, for biomedical applications; flexible interconnects for microelectronics, and sensors to detect fatigue, impact and large strain for aerospace applications. This novel material may be formed as a conformal coating on nearly any substrate or as free standing films.

This paper presents an update concerning the properties of a new class of nanostructured materials that exhibit the combined properties of low mechanical modulus and high electrical conductivity. Such "Metal RubberTM" materials are formed by molecular-level self-assembly processes. Material synthesis and properties are described. Potential applications for space-based photonics and electronics are in flexible polymer-based electrodes and opto-electronic devices.