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arXiv · 1410.1765

Elastocapillary folding using stop-programmable hinges fabricated by 3D micro-machining

A. Legrain·J. W. Berenschot·N. R. Tas·L. Abelmann
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Abstract

We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of 70.6$\pm$0.1° and demonstrate the feasibility of such accurate micro-assembly with a final folding angle of 90°. The folding angle is defined by stop-programmable hinges that are fabricated starting from silicon molds employing accurate three-dimensional corner lithography. This nano-patterning method exploits the conformal deposition and the subsequent timed isotropic etching of a thin film in a 3D shaped silicon template. The technique leaves a residue of the thin film in sharp concave corners which can be used as an inversion mask in subsequent steps. Hinges designed to stop the folding at 70.6° were fabricated batchwise by machining the V-grooves obtained by KOH etching in (110) silicon wafers; 90° stop-programmable hinges were obtained starting from silicon molds obtained by dry etching on (100) wafers. The presented technique is applicable to any folding angle and opens a new route towards creating structures with increased complexity, which will ultimately lead to a novel method for device fabrication.

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A. Legrain, J. W. Berenschot, N. R. Tas, L. Abelmann. 2014-11-07. Elastocapillary folding using stop-programmable hinges fabricated by 3D micro-machining. https://doi.org/10.1371/journal.pone.0125891

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