Contributed editorial appearing in
Scientific Computing & Instrumentation 18:11, October 2001, pg. 16.
At the December 29, 1959 annual meeting of the American Physical Society held at the California Institute of Technology, Physicist Richard P. Feynman delivered a watershed talk titled “There’s Plenty of Room at the Bottom.” Ruminating the possible benefits and applications of miniature, massively integrated circuits in a time of room-sized, multi-ton computers predating the March 1960 patent of the laser, Feynman looked to biochemistry for examples of how nature solved problems of manufacturing on an extremely small level. He marveled at the stark contrast between the human and natural approaches to manufacturing; the former successively mining, refining, purifying, and molding bulk materials excavated from the ground, while the latter constructs elegant, self-assembling, high-level cognizant organisms from pure atomic materials selected from the periodic table.The 1-nanometer (nm) resolution of the 1950s electron microscopes were unable to image individual 0.25-nm diameter atoms. He envisioned a device such as the modem scanning tunneling microscope (STM) capable of imaging individual atoms at 0.01-nm resolution in hopes that the fundamental atomic structure and spatial configuration of biological molecules could he viewed and examined directly. Seven short years after Watson and Crick deduced the structure of DNA in 1953, Feynman marveled at nature’s ability to store, transfer, and utilize genetic information using molecules comprised of merely 50 atoms while 50-atom diameter electronic wires are still 15 times smaller than the 0.18-micron wires utilized by today’s integrated circuits.
Discussions of nanometer-sized structures, circuits, and machines evolved into the area of research now known as Microelectromechanical Systems or MEMS. Three general thrusts of MEMS research are concerned with 1) the miniaturization of current technology, 2) the creation of new microscopic devices through the assemblage of atoms and molecules, and 3) the utilization, function and deployment of MEMS devices.
Miniature pressure, acceleration, and pressure sensors have been developed and used extensively by the medical industry since the 1980s to monitor blood pressure, respiration rate, eye pressure, body temperature, and patient activity. In addition to being rugged and inexpensive to manufacture, the small physical size of these MEMS sensors minimizes their intrusive effects on the patient. This past August, the FDA approved the use of an ingestible “camera in a capsule” wireless endoscope system developed by Israel-based Given Imaging Ltd. The $450 disposable camera capsule consists of a light source, color video camera, batteries, and a wireless transmitter. After being swallowed by the patient, images of the gastro-intestinal tract are received by an array of external antennae affixed to the abdomen and connected to a digital receiver worn around the patient’s waist. The images and corresponding capsule locations are downloaded from the receiver to a personal computer after the capsule is excreted naturally.
MEMS devices that are assembled from individual atoms are the results of developments in “molecular nanotechnology”—an area of research that takes its cues from biological systems. The Foresight Institute in Palo Alto, California, hosts an annual conference in this field where researchers demonstrate working molecular devices. The biochemical-to-mechanical analogs include using cellulose as struts, collagen as cables, intermolecular forces as fasteners, sigma bonds as bearings, membranes as pumps, binding sites as clamps, ribosomes as assembly lines, and DNA as numerical control systems.
The third area of concomitant MEMS research is in the deployment and coordination of microscopic sensor array networks. To facilitate sensor measurements over a large area, a large number of MEMS sensors must be deployed and expected to communicate their results to a central data acquisition station and perhaps each other. The Defense Advanced Research Projects Agency (DARPA) sponsored such research into massively distributed sensor arrays at the University of California, Berkeley in 1998. The goal of the project was to develop a submicrowatt-powered integrated circuit containing signal conditioning circuits, a temperature sensor, an A/D converter, microprocessor, SRAM, wireless communication circuits, and power control circuits - having a total package footprint of a cubic millimeter. Coined the “Smart Dust” project, these small sensors or “motes” have defense applications such as battlefield surveillance, intelligence gathering, and chemical/biological weapon hunting.
The Center for Information Technology Research in the Interest of Society (CITRIS), a partnership between the University of California, corporate, and government research laboratories, is developing commercial applications of this technology. Earlier this year, CITRIS demonstrated a prototype network consisting of 50 smart motes distributed throughout a building on the Berkeley campus and used to manage and optimize the building’s heating and cooling requirements. CITRIS anticipates a savings of up to $8 billion in energy costs if distributed sensor systems are installed in buildings throughout the state of California. As we continue to advance the technology of the small, let us hope that our foresight is as expansive and prescient as Professor Feynman’s.
