Although the excitement about nanotechnology and its prospective uses is generally well founded, there are many inescapable requirements that must be considered for the successful development and integration of nanotechnology sensors. These requirements include those imposed by physics, chemistry, biology, engineering, and commerce.

For example, as nanotechnologies are integrated into macro-sized systems, it will be necessary to provide for and control the flow of matter, energy, and information between the nanometer-scale and macro-scale systems. Calibration of nano-enabled sensors can be problematic if very small amounts of analyte and reagent materials are involved. It must be remembered that the size of most sensor systems is determined by the scale of the computer, memory, and radio chips, and (especially!) by the batteries and antennas. This is true for both micro- and nanoscale sensors.

Intensified Design Problems

Many of the design considerations for nanoscale sensors are similar to those of microsensorsnotably, interface requirements, heat dissipation, interferants, and noise (both electrical and mechanical). Each interface in a microsystem is subject to unwanted transmission of electrical, mechanical, thermal, and possibly chemical, acoustical, and optical fluxes. Dealing with unwanted molecules and signals in very small systems often requires ancillary equipment and the use of low temperatures to reduce noise.

Flow control is especially critical in chemical and biological sensors into which gaseous or liquid analytes must be brought and from which they are expelled. The very sensitive, tailored surfaces in molecular sensors, chemical as well as biological, are subject to degradation by interfering substances, heat, and cold. One of the attractions of nanotechnology is the chance to make hundreds of sensors in a small space so that sensors that have degraded can be ignored in favor of fresh sensors to prolong the useful lifetime of a system containing them.

The Risks of Commercialization

The path from research to engineering to products to revenues to profits to sustained commercial operations is difficult for technologies of any scale. It is particularly challenging for new nanotechnologies, and not only because of the common reluctance to specify new technologies for high-value systems. The reality is that most nanoscale materials are currently difficult to produce in large volumes, so unit prices are high and markets limited. Costs will decrease over time, but it may be difficult for small companies to make enough profit soon enough. A recent review has focused on the commercialization of nanosensors.lH!



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