This paper describes the design, fabrication and testing of an electrostatically actuated microshutter used as an active shadow mask to pattern evaporated materials. The microshutter and its comb-drive actuator are built on the device layer of an SOI wafer. Deep reactive ion etching (DRIE) is used to pattern both the device layer and etch a through-wafer hole through which the evaporated materials travel. The actuation voltage of the device is about 30 volts, its resonant frequency is several kHz. The microshutter integrated with an x-y-z manipulator was used to print patterns of organic material and metal on glass substrates in vacuum with a resolution of 30 microns. This printing scheme could enable the patterning of large area organic optoelectronic devices on diverse substrates.

Deep reactive-ion etching

Shadow mask

10.1109/sensor.2005.1497350

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Citations (5)

Evaporation and Deposition of Colloidal Binary Droplets

Physical Review Applied (2022)

Gun Oh Woojun Jeong Narina Jung Sung Hoon Kang Byung Mook Weon

Droplet evaporation is a versatile process to deposit solute materials on a substrate unless it induces solute accumulation at droplet perimeter because of outward capillary flows. Despite many efforts to generate inward Marangoni flows to suppress outward capillary flows, it is challenging to control Marangoni flows in colloidal droplets that include binary solvents. To understand and manipulate Marangoni flows in colloidal binary droplets, we investigate droplet evaporation and deposition dynamics by changing the mass ratio of binary solvents. We show that island deposits emerge when Marangoni flows overwhelm capillary flows during most evaporation. The formation of island deposits in colloidal binary droplets would be a helpful route to achieve uniform deposits of colloidal particles or nanoparticles.

Deposition

Colloidal particle

10.1103/physrevapplied.17.024010

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Citations (15)

Complex ordered patterns in mechanical instability induced geometrically frustrated triangular cellular structures

Bulletin of the American Physical Society (2014)

Sung Hoon Kang Sicong Shan Andrej Košmrlj Wim L. Noorduin Samuel Shian

Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.

Source

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Citations (11)

Meniscus Lithography: Evaporation-Induced Self-Organization of Pillar Arrays into Moiré Patterns

Physical Review Letters (2011)

Sung Hoon Kang Ning Wu Alison Grinthal Joanna Aizenberg

We demonstrate a self-organizing system that generates patterns by dynamic feedback: two periodic surfaces collectively structure an intervening liquid sandwiched between them, which then reconfigures the original surface features into moir\'e patterns as it evaporates. Like the conventional moir\'e phenomenon, the patterns are deterministic and tunable by mismatch angle, yet additional behaviors---chirality from achiral starting motifs and preservation of the patterns after the surfaces are separated---emerge uniquely from the feedback process. Patterning menisci based on this principle provides a simple, scalable approach for making a series of complex, long-range-ordered structures.

Moiré pattern

Meniscus

Pillar

Chirality

10.1103/physrevlett.107.177802

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Citations (36)