A. Diaz and E. Rothwell Michigan State University
The research objective of this award is to develop a new methodology for the design of metamaterials, and the design of systems that use metamaterials. The proposed methodology is intended to enable designers to rigorously and methodically explore novel, complex metamaterial designs, address complex, multifunctional performance specifications and to integrate results in design of RF (radiofrequency) systems. Optimization algorithms based on topology optimization methods and inverse homogenization problems in material design will be used to support the methodologies developed in this research. Design of electrically small RF systems will be used as a model for design using metamaterials. A fabrication/testing/validation program will be used to validate the methodology and to adjust the computational procedures to account for factors such as size and edge effects.
If successful, the results of this research will provide a rigorous and practical foundation for the design of devices that are likely to generate new growth in a number of high-technology industries: personal communications, medical diagnostics, sensors. When applied to the design of electrically small antennas, this research will help meet increasing demands for miniaturization in personal communication devices and wireless sensors. While demonstrating the process of integration of metamaterials in RF systems, the research will also facilitate understanding of how to insert metamaterials in components and devices used in other areas of technological importance. The experimental program will provide guidance to the community on how to evaluate the performance of metamaterials. More broadly, the integration of this research in education and outreach activities will enhance programs for undergraduate students through the introduction of multi-disciplinary design-build-test projects in electrical and mechanical engineering and through the development of web-based tools that expose discoveries to a broad audience in a format suitable for exploration and learning.
A huge challenge for electronics manufacturers is keeping up with the demand for more systems squeezed into smaller spaces. Think of the typical modern smart phone, which now does the duties of several former devices – a phone, a camera, a GPS unit, a music player, an organizer, a voice recorder, an internet browser, a remote control. A particularly crucial area for industry is wireless sensors, since tiny sensors embedded in a wide variety of products can monitor the health of the product throughout its life cycle. Sensors are also used to provide feedback to users about the operation of systems as varied as automobiles, washing machines, and even their own bodies. For instance, patients with glaucoma may have tiny wireless sensors embedded directly into their eyes to report the pressure internal to the eye. Crucial to all of these applications is the ability to make the wireless components as small as possible. Miniaturizing components for wireless systems is very difficult, so researchers have turned to using materials with exotic properties. Most exciting are man-made materials, which can be manufactured to have electronic properties not found in nature. These are called "metamaterials," and are made by embedding small metallic inclusions into a plastic type material. Until recently, these materials were designed using simple inclusions, and their properties were not easily adapted to specific applications. Our work has shown how to design metamaterial structures with specified properties by optimizing complicated templates, producing odd shaped structures that cannot be anticipated using existing approaches. More importantly, the structures may be optimized while actually in the presence of the device they are being used with. Until now, the materials were designed completely separate from the device, and often did not work as anticipated when brought together with a device or system. As an example, we can create metamaterial structures that allow the area occupied by antennas used in sensors to be reduced by a factor of 16, without seriously degrading the performance of the antenna. This means that the sensor can be made much smaller so that it can be placed into a tiny device, or more sensors can be placed in the same area. We can also create other miniaturized electronic devices important to wireless systems, such as filters, using our optimization techniques. One serious drawback with metamaterials is that they perform well over only a small band of frequencies. A sensor designed to work well at, say, the GSM cell phone frequency of 850 MHz may not operate well at the 2.4 GHz WI-FI frequency. We have developed methods to tune metamaterials so that their frequency of operation may be changed. In particular, we have applied the principles of origami to develop structures that may be tuned by folding them much in the same way as the pleats of an accordion. By moving the pleats in and out, the interaction between the metamaterial inclusions changes, and thus the dependence of the structure on frequency changes. This approach as tremendous potential, since there are a vast number of ways in which surfaces may be folded, and only a few of these have been investigated.
