Kee-Bong Choi

A flexure-based scanner for a fully bidirectional operation driven by a differential piezo force

In this paper, a flexure-based scanner driven by a differential piezo force is proposed for a fully bidirectional operation. The differential piezo force is generated by piezo-driven actuation mechanisms that are arranged antagonistically. The scanner consists of a target platform, a double compound linear guide mechanism, and two identical actuation mechanisms that are piezo-driven mechanical amplifiers that magnify the displacement of a stack-type piezo actuator. The actuation mechanisms are symmetrically mounted on both sides of the target platform, and generate antagonistic pull forces. The difference in the pull forces causes the motion of the target platform. Due to its symmetric structure, the proposed scanner can conduct a bidirectional motion along the positive and negative directions. Through design and analysis, the scanner is manufactured, and then the bidirectional motion and control performance of the scanner are demonstrated.

Nanoimprint lithography with a focused laser beam for the fabrication of nanopatterned microchannel molds

We present a process based on nanoimprint lithography for the fabrication of a microchannel mold having nanopatterns formed at the bottoms of its microchannels. A focused laser beam selectively cures the resist in the micrometer scale during nanoimprint lithography. Nanopatterns within the microchannels may be used to control microfluidic behavior.

Laser-assisted selective lithography of reduced graphene oxide for fabrication of graphene-based out-of-plane tandem microsupercapacitors with large capacitance

We present a laser lithography technique that uses a focused laser beam to fabricate out-of-plane tandem microsupercapacitors (MSCs) from reduced graphene oxide (rGO) with large areal capacitance. By controlling the depth of focus in a laser beam focused by an objective lens during laser lithography on a graphene oxide (GO) film, a rGO/GO/rGO structure is formed in the GO film, and subsequently, two independent interdigitated electrodes (IDEs) were fabricated on the top and bottom surfaces of the GO film. The out-of-plane tandem MSC with a parallel assembly of two rGO-IDEs showed two times larger areal capacitance than an in-plane single MSC with one rGO-IDE in the same MSC device footprint. The laser-assisted selective lithography technique using a focused laser beam developed in this study can be further applied to improve the energy density of MSCs without increasing the electrode area by vertically stacking multiple out-of-plane tandem IDEs.

Double-Pitch Dual Grating Method for Detecting the Axial Offset in Roll System

We propose a dual grating alignment technique for roll-to-roll positioning which allows achieving nanometer scale alignment by using micro-size marks. The high precision alignment system were designed and manufactured. It was confirmed that the optical system was properly adjusted and fully aligned with the dual gratings. The experiment and computer simulation results were presented. Alignment accuracy below 50 nm was achieved.

A Piezo-Driven Miniaturized XY Stage with Two Prismatic-Prismatic Joints Type Parallel Compliant Mechanism

In this paper, a miniaturized stage with two prismatic-prismatic joints (2-PP) type parallel compliant mechanism driven by piezo actuators is proposed. This stage consists of two layers which are a motion guide layer and an actuation layer. The motion guide layer has 2-PP type parallel compliant mechanism to guide two translational motions, whereas the actuation layer has two leverage type amplification mechanisms and two piezo actuators to generate forces. Since the volume of the stage is too small to mount displacement sensors, the piezo actuators embedding strain gauge sensors are chosen. With the strain gauge-embedded piezo actuators, a semi-control is implemented, which results in hysteresis compensation of the stage. As the results, the operating range of 30 µm, the resolution of 20 nm, and the bandwidth of 400 Hz in each axis were obtained in the experiments.

A new mold structure to replicate patterns over 1 microm in depth for substrate conformal imprint lithography.

This paper shows an improved mold replication process that uses polyurethane acrylate (PUA) and polyethylene terephthalate (PET) for the fabrication of an ultraviolet (UV) imprinting mold used in substrate conformal imprint lithography (SCIL). With the conventional replication process, which uses hard polydimethylsiloxane (h-PDMS) as a pattern layer, it is difficult to detach the mold from a silicon master for metal oxide semiconductor field effect transistor (MOSFET) that has patterns with over 1-micron depth. However, the method proposed in this paper allows us to easily replicate patterns that have more than 1-micron depth. The key idea of this method is to use PET film as a bonding layer to attach the PUA layer to the polydimethylsiloxane (PDMS) cushion layer to overcome the weak the adhesion force between the PUA and PDMS layer. We demonstrate how to make the modified replica mold and present imprinting results obtained using this replica mold in the SCIL process.