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

TL;DR

This paper demonstrates the integration of conductive platinum hinges into capillary self-folded micro-objects, enabling electronic functionalities while maintaining high fabrication yield and mechanical robustness.

Contribution

Introduction of bi-layer conductive hinges in capillary origami micro-objects, with analysis of fabrication yield, durability, and electrical performance.

Findings

High fabrication yield for short hinges (77%)

Hinges withstand small bending radii of 5 μm

Conductive hinges endure high current densities (~1.6×10^6 A/cm²)

Abstract

Recently, we demonstrated controllable 3D self-folding by means of capillary forces of silicon-nitride micro-objects made of rigid plates connected to each other by flexible hinges [1]. 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 {\mu}m. The yield reduces to (18 +/- 2) % when the length increases above 100 {\mu}m. 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 {\mu}m, 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.