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SYSTEMS 7 TOPIC 2: SYSTEMS Three papers were presented in this session, one by Kwan Kwok, DARPA, one by Rich Fletcher, the Massachusetts Institute of Technology (MIT) and TagSense, Inc., and one by Chris Murphy, NRC Board on Chemical Sciences and Technology. APPLICATIONS OF MOLECULAR ELECTRONICS TECHNOLOGY (MOLEAPPS) PROGRAM Kwan Kwok reviewed the goals and achievements to date of the new 5-year DARPA MoleApps program, which aims to apply molecular-scale electronics technology to the development of ultradense molecular electronic computer processors (this thrust is called MoleComputing) and molecular electronic sensor systems (MoleSensing). For the purposes of the MoleApps program, molecular-scale electronics technology refers to using single molecules, small numbers of molecules, nanoparticles, nanoscale metallic and/or semiconductor wires, nanotubes, and so on as electronic components. The goal of the MoleComputing thrust is to develop a prototype molecular (no-silicon) electronic computer processor having local molecular device densities of 1011/cm2 and a clock rate of at least 10 kHz and consuming no more than 10 W/cm2 of power. Such a processor would be equivalent in complexity to a 1971-vintage microprocessor such as the Intel 4004 but have an area 100,000 times smaller. It would have to be compatible with molecular memory devices such as those being developed in the concurrent DARPA programs, Moltronics, for example, a team of researchers from Rice and Yale Universities, is developing a 10 ÂµmÃ10 Âµm 16-kbit memory consisting of an ultra-high-density network of molecular wires and switches that will fit on a human cell. The manufacturing processes to produce such components in bulk do not exist yet, and such molecular memories are affected by, among other things, cosmic rays and incomplete reactions, but they will be self-repairable and fault-tolerant (able to operate with up to 10 percent defects). In 2001, researchers from Hewlett-Packard and the University of California at Los Angeles produced crossed-wire memory devices by sandwiching perpendicular layers of nanoscale wires (reminiscent of the ferrite core memory structures used in the early days of computers). The pitch (spacing between parallel wires) was 33 nm in those devices, and more recent efforts have reduced the pitch to 20 nm. The goal of the MoleSensing thrust is to develop a prototype molecular electronic sensor system having at least 1,000 nanosensors per square micrometer (1011 per square meter) and sensitivity and discrimination equivalent to a dog's nose. DARPA has funded research on artificial dog's noses for a number of years, but progress has been slow. The sensor should be able to uniquely identify any of 255 different chemical and biological agents in concentrations as small as 500 parts per trillion. It should have a chemical response time of no more than 10 seconds after exposure to the sample and an electrical