Capillary origami of micro-machined micro-objects: Bi-layer conductive hinges

Abstract

Recently, we demonstrated controllable 3D self-folding by means of capillary forces of silicon-nitride microobjects made of rigid plates connected to each other by flexible hinges (Legrain et al., 2014). In this paper, we introduce platinum electrodes running from the substrate to the plates over these bendable hinges. The fabrication yield is as high as (77 ± 2)% for hinges with a length less than 75 μm. The yield reduces to (18 ± 2)% when the length increases above 100 μm. Most of the failures in conductivity are due to degradation of the platinum/ chromium layer stack during the final plasma cleaning step. The bi-layer hinges survive the capillary folding process, even for extremely small bending radii of 5 μm, nor does the bending have any impact on the conductivity. Stress in the different layers deforms the hinges, which does not affect the conductivity. Once assembled, the conductive hinges can withstand a current density of (1.6 ± 0.4) × 10 6 A/cm 2 . This introduction of conductive electrodes to elastocapillary self-folded silicon-based micro-objects extends the range of their possible applications by allowing an electronic functionality of the folded parts.

Open Microfluidic Capillary Systems

“…Surface modification can be essential to the operation of a microfluidic channel. Many surface modification techniques have been developed, including plasma pretreatment and silanization, chemical vapor deposition, UV irradiation, photochemical grafting, nanomaterial deposition, and atomic layer deposition, among others. , Some key methods of surface preparation require exposure to an environmental treatment, such as plasma treatment to render the surface wettable ,,,, or chemical vapor deposition to protect the material from solvents ,,,, (Figure B). In closed systems, the surface modification may be performed before bonding, in which case it may affect the bonding efficiency or be affected by the bonding process (e.g., temperature or solvents) .…”

Assembly and Self‐Assembly of Nanomembrane Materials—From 2D to 3D

“…However, many desired 3D structures demand spatial localization of the bending, as in the case of origami. Engineered variation in thickness was found to be able to guide folding deformation at specific locations and thus provided such capability . Simulation of the self‐assembly process proved that when the thickness ratio was relatively small (e.g., <1/3), the thick regions underwent negligible deformation while the thin ones accommodated the compression via folding, and the maximum strains occured at these regions (so‐called crease) .…”

Nano-origami: Art and function

“…Completing the analogy with origami, on the other hand, requires "folding" or "creasing" function in the device. Foldability is introduced via hinges that are thinner and/or more compliant, deposited and patterned into the structure that will become the 3D nano-device [8,[22][23][24][25], and actuated via differential strain, which is locally dominant at the hinges. Many more shapes and expanded capabilities are possible with the judicious insertion of compliant hinges.…”