Design News, April 2013

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Cover Story Self-Assembled Devices May T ransform Manufacturing The line between materials and machines will blur when modular, self-reconfigurable robots and self-assembling engineered DNA bricks change the rules of product manufacturing. By ann r. Thryft, Senior Technical Editor, Materials & assembly E ngineers are developing multiple technologies to create devices that self-assemble or selfreconfigure, from synthetic DNA to robotic building blocks. Some may eventually create materials tailored for specific functions, or energy-harvesting and drug-delivery devices. Others may be used to copy objects for rapid prototyping, make replacement parts for other systems, or repair themselves. Self-assembling and selfreconfiguring robots that change their shapes and functions to fit the task and environment may serve as rescue robots and planetary explorers, or completely replace the manufacturing processes of certain consumer goods. All of these techniques are still in R&D. Until recently, nanotechnology using DNA to build tiny, programmable structures focused mostly on DNA origami. Here, a long strand of biological DNA forms a backbone, with smaller strands bound to its segments to create different shapes. Researchers at Harvard's Wyss Institute for Biologically Inspired Engineering traveled a different path. Led by Peng Yin, assistant professor of systems biology at Harvard Medical School and a core faculty member at Wyss, the team programmed short synthetic strands of DNA as building blocks, called single-stranded tiles (SSTs). These self-assemble into precise shapes, such as letters and numbers. During self-assembly each 3 nm x 7 nm SST binds to as many as four other tiles if they have comple- mentary DNA sequences. There is no backbone required, so the number of distinct shapes that can be built is high, more than 100, and tiles can be independently added or removed. Recently, the team extended its work to three-dimensional objects: instead of tiles, the strands now form bricks. Each brick has a distinct sequence of nucleotides, but an identical shape. The team used the 3D bricks to build 102 distinct shapes, somewhat like LEGOs. "We want to use DNA as information-carrying, selfassembling molecules," Yin said in an interview. "We're pursuing nanotechnology as a methodology for developing self-assembling devices because it is the only way to make the structures we want, which need small, nanometer-scale particles as building blocks. These are on a different scale than self-assembly methods based on macro-scale building blocks." Yin said the technology has several potential uses. In clinical applications, it can be designed to detect diseases, and perhaps also deliver cancer-killing drugs. It can also be used to increase the throughput of nanofabrication processes for making materials used in photonics and energy applications, such as highly efficient nanoelectronics or energy-harvesting devices, or even for nanodevice rapid prototyping. Larger robotic building blocks have been developed by many different researchers. Some of the best-known self- Design News | april 2013 | www.d esign n –38–

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