title: Elasto-Capillary Folding Using Stop-Programmable Hinges Fabricated by 3D Micro-Machining.
abstract: We show elasto-capillary folding of silicon nitride objects with accurate folding angles between flaps of (70.6 ± 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 has potential to achieve 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.
authors.affiliation: MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
authors.forename: Antoine
authors.initials: A
authors.lastname: Legrain
authors.affiliation: MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
authors.forename: Erwin J W
authors.initials: EJ
authors.lastname: Berenschot
authors.affiliation: MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands.
authors.forename: Niels R
authors.initials: NR
authors.lastname: Tas
authors.affiliation: MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands; KIST Europe, Saarbrücken, Germany.
authors.forename: Leon
authors.initials: L
authors.lastname: Abelmann
mesh_terms: D004548:Elasticity; D066330:Printing, Three-Dimensional; D012825:Silicon / Q000737:chemistry*
chemical_list: D012825:Silicon