Self-transport and self-alignment of microchips using microscopic rain

Abstract

Alignment of microchips with receptors is an important process step in the construction of integrated micro- and nanosystems for emerging technologies, and facilitating alignment by spontaneous self-assembly processes is highly desired. Previously, capillary self-alignment of microchips driven by surface tension effects on patterned surfaces has been reported, where it was essential for microchips to have sufficient overlap with receptor sites. Here we demonstrate for the first time capillary self-transport and self-alignment of microchips, where microchips are initially placed outside the corresponding receptor sites and can be self-transported by capillary force to the receptor sites followed by self-alignment. The surface consists of hydrophilic silicon receptor sites surrounded by superhydrophobic black silicon. Rain-induced microscopic droplets are used to form the meniscus for the self-transport and self-alignment. The boundary conditions for the self-transport have been explored by modeling and confirmed experimentally. The maximum permitted gap between a microchip and a receptor site is determined by the volume of the liquid and by the wetting contrast between receptor site and substrate. Microscopic rain applied on hydrophilic-superhydrophobic patterned surfaces greatly improves the capability, reliability and error-tolerance of the process, avoiding the need for accurate initial placement of microchips, and thereby greatly simplifying the alignment process.

Large-scale efficient water harvesting using bioinspired micro-patterned copper oxide nanoneedle surfaces and guided droplet transport

“…The experimental setup had a relative humidity above 90% and the temperature was maintained at 24 C throughout the experiments. The size of the droplets in this case typically ranges from 1 to 5 mm in diameter, 59 which is similar to those reported elsewhere 38 and comparable to that of atmospheric fog. Then, the volume of water was collected and measured with a weight balance at intervals of 20 min over a period of 2 h. For the onset of dripping experiments, the surfaces used were 15 mm  15 mm in dimensions and were freshly and independently fabricated.…”

Surface tension-driven self-alignment

“…Compared to the single droplet methods, the parallel stochastic methods can produce a huge amount of individual droplets of down to femtoliter volumes, which makes it highly efficient. The parallel stochastic method is most suitable for water disposition, 54,92,96 even though other liquids can also be handled. As the deposition takes place on the full substrate, droplets on undesired regions of the substrate (e.g., outside the receptors) should be removed by post-processing (e.g., vaporization) after the self-alignment step, unless their existence is compatible with the subsequent processing steps.…”

“…Particularly, self-transport and self-alignment of microcomponents was reported, whereby even a gap of tens of microns between a component and its shape-matching receptor, defined chemically on a superhydrophobic substrate, is bridged by means of microscopic rain. 96…”

Modular Lego‐Electronics

“…Several other reported methods for self-assembly use the surface tension in combination with either solder bumps [5][6][7] , magnetic [8,9] or electrophoretic [10,11] forces, or capillary transport. [12] Smith et al and Jacob et al [13] have reported higher yields for the assembly process in their works.…”