A study suggests that the central-western Greenland Ice Sheet (GIS) is approaching a critical transition and will undergo significantly enhanced melting in the near future.
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Edited by George M. Whitesides, Harvard University, Cambridge, MA, and approved October 2, 2009 (received for review July 2, 2009)
Abstract
Fabrication of 3D electronic structures in the micrometer-to-millimeter range is extremely challenging due to the inherently 2D nature of most conventional wafer-based fabrication methods. Self-assembly, and the related method of self-folding of planar patterned membranes, provide a promising means to solve this problem. Here, we investigate self-assembly processes driven by wetting interactions to shape the contour of a functional, nonplanar photovoltaic (PV) device. A mechanics model based on the theory of thin plates is developed to identify the critical conditions for self-folding of different 2D geometrical shapes. This strategy is demonstrated for specifically designed millimeter-scale silicon objects, which are self-assembled into spherical, and other 3D shapes and integrated into fully functional light-trapping PV devices. The resulting 3D devices offer a promising way to efficiently harvest solar energy in thin cells using concentrator microarrays that function without active light tracking systems.
Footnotes
- 1To whom correspondence should be addressed. E-mail: r-nuzzo{at}illinois.edu
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Author contributions: X.G., K.J.H., J.A.L., and R.G.N. designed research; X.G., H.L., B.Y.A., E.B.D., and K.J.H. performed research; X.G., K.J.H., and R.G.N. analyzed data; and X.G., H.L., K.J.H., J.A.L., and R.G.N. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Two- and three-dimensional folding of thin film single-crystalline silicon for photovoltaic power applications
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