A technique for the self-assembly of polymeric microstructures, which works by using a guiding ‘rail’ mechanism, is reported online this week in Nature Materials. The method could be used for manufacturing two-dimensional patterns of living cells for tissue engineering and manipulating silicon devices for microchip packaging.

On the micrometre scale, conventional assembly techniques such as robotics are often not applicable, and can result in errors in the final product. Sunghoon Kwon and colleagues devised a way to guide the assembly of microstructures within microfluidic channels, and make complex structures composed of more than 50 individual ones. All the microstructures used at the start of the process are incorporated in the product and different shapes can also be guided to specific locations, allowing the construction of two-dimensional representations of, for example, the Eiffel Tower, a Greek temple and a computer keyboard.

The method works by introducing a groove or ‘rail’ into the top surface of the channels and a complementary shape in the polymeric microstructure. In contrast to other fluidic assembly routes, the structures are guided along the rail rather than moving in the exact direction of fluid flow in the channel.