A new silicon microstructural solution announced this month is so powerful in creating 3D patterns from 2D surface machining that I just have to share. The figure shows 3D silicon microstructures formed by compressive buckling. The method can be used to create objects with features as small as 100 nm that could be useful for developing new technologies for medicine, energy storage and even brain-like electronic networks. Note that the silicon is surface-machined using standard MEMS processes, and that all manner of silicon circuitry and thin-film sensors could be integrated into this silicon.
Colleagues from the University of Illinois at Urbana-Champaign, Northwestern University, Zhejiang University, East China University of Science and Technology, and Hanyang University created the new 2D-to-3D fabrication technique. Their trick is that after all other surface machining they chemically modify the square anchors in the surface pattern such that they are sticky. After the 2D pattern is released it is transferred onto a sheet of stretched silicone rubber. Allowing the rubber to relax back to its natural shape draws the squares toward each other, while the rest of the silicon buckles upwards. Using this type of controlled buckling, the team managed to produce a variety of elaborate 3D shapes.
The researchers even produced structures with multiple levels of elevation by designing shapes in which the relief of stress in the initial 2D shape would create further buckling, raising another part of the shape further. John Rogers of the University of Illinois at Urbana-Champaign, who is part of the micro-buckling team looks forward to an electronic cell or tissue scaffold, “A lot of the people that we talk to are enthusiastic about what you can do when you go from a passive scaffold to something that embeds full electronic functionality.”
The research is published in Science.
—E.K.
