HANCOCK, N.H. Biotechnology has emerged as a major conference theme of late, and the fall meeting of the Materials Research Society, held last week in Boston, was no exception, with biomaterials presentations peppering the weeklong series of research reports. Since MRS is involved in virtually every area of modern industry and technology, its shift in emphasis from inorganic to organic and biological processes may suggest a trend for society as a whole.
A plenary lecture by Leigh Canham, co-founder and chief scientific officer at pSiMedica Ltd. (Malvern, England) may also be a bellwether for the electronics industry. Canham has pioneered the application of porous silicon to biomedical applications and believes that silicon can be fabricated in forms that are highly compatible with living tissue. His talk, "Interfacing Silicon Technology with the Human Body: Bionics in the New Millennium," was bullish on silicon electronics' prospects for use in medical diagnosis and therapy. He predicted that MEMS will play a large role in implantable therapeutic devices as sensors and actuators, and for electrical stimulation of tissue.
Canham's own career may indicate what is in store for semiconductor technologists. During his tenure as a semiconductor researcher at England's Defense Evaluation Research Agency in the early 1990s, he discovered that porous silicon could emit light. IC applications were difficult to implement because of the material's high chemical reactivity. But the finding revealed a key link between silicon and biological processes, leading Canham to shift his research priorities toward biomedical applications.
Canham described medical applications being pursued for a biocompatible form of silicon, Biosilicon, that was developed at his company. Drug delivery, zapping tumor cells with targeted radioactive "seeds" and electronic fabrics that merge with tissue, are some of the developments being pursued at pSiMedica.
An introductory presentation for a session track on biological materials assembly by Nadrian Seeman from New York University emphasized the importance of DNA as a catalyst for creating complex three-dimensional structures at the nanometer scale. DNA combines an essentially digital structure with the ability to form unique 3-D bonds between particles. That is leading researchers to develop computer-generated algorithms that can chemically direct the assembly of complex geometric structures.
The conference also revealed the rapid growth of molecular-imprint technology, which stands at the interface between biology and industrial technology. The basic technique is to use polymer films as a pliable template for biological molecules. For example, protein molecules of interest are pressed into a polymer film and then removed, leaving a physical mold of the molecule's shape.
The film can then be hardened and used to detect that particular molecule since the complex shape will bind to only that protein. Schemes that tag protein molecules in a solution with phosphorescent particles can determine the presence of the protein using optical inspection of the polymer film.
But that is only one possible application for molecular-imprint processes. A spin-off technique has produced nanoimprint lithography for silicon VLSI production that have recently reached market. Those systems can produce circuits at feature sizes beyond current optical lithography methods with the same parallel throughput advantage for manufacturing.
Polymer films are imprinted with silicon templates, created by electron-beam lithography and then hardened to create etch masks.