By Gary Thomas
A research team comprising Caroline Ross and colleagues from the Massachusetts Institute of Technology (MIT) has developed a technique to build intricate three-dimensional (3D) structures utilizing self-assembling polymer materials that are capable of creating small junctions and wires.
Caroline A. Ross
According to the researchers, it is the first time that complex 3D structures with various independent patterns on different layers have been produced. The study results have appeared in the Science journal. The work involved the creation of an array of small posts over a silicon substrate followed by coating of the surface with block copolymers, which tend to self-assemble into lengthy cylindrical structures. The researchers set the junctions, bends, angles and spacing of the cylinders that formed on the surface through the careful control of the posts’ initial spacing. These posts allowed the researchers to control the cylinders’ two layers separately, thus enabling the formation of intricate 3D structures.
Lead author, Amir Tavakkoli informed that the new technique is simple. The new system not only enabled control over the wire alignment but also demonstrated the possibility of creating junctions and sharp bends at designated locations.
To realize the system, the researchers needed to tackle a number of challenges, said Kevin Gotrik, a MIT graduate student.
Graduate student Adam Hannon stated that using computer models of the 3D structures, the research team studied the impact of various post configurations on the two-layer 3-D structure. The researchers then compared these models with most potential structures explored in the lab to better understand the ways of controlling the structures that formed.
Although, until now, the researchers have only created two-layer configurations, it is possible to create three-layer configurations with complete control over the alignment of structures on every layer intact, said Alfredo Alexander-Katz, an Assistant Professor of materials science and engineering.
The MIT lab’s electron-beam lithography is the key enabling technology, which forms 10-nm-width cylindrical posts with accurately controlled positioning. These posts help the self-assembling cylinders to take position at designated locations. Ross stated that so far, the research team has created cylinders having a width much smaller than 15 nm, which is half the width of thinnest wires used in present microchips.
Although technologies used in this study are compatible with present production systems in the semiconductor industry, still more research is required to perform actual chip production. The researchers expect to create a basic electronic device utilizing this technique by next year. According to the researchers, the method not only creates wires on a silicon chip but also produces 3D arrays of other materials like DNA molecules or proteins to develop drug-delivery systems or biological detectors.