Hierarchically Porous, Laser-Pyrolyzed Carbon Electrode from Black Photoresist for On-Chip Microsupercapacitors.

We report a laser-pyrolyzed carbon (LPC) electrode prepared from a black photoresist for an on-chip microsupercapacitor (MSC). An interdigitated LPC electrode was fabricated by direct laser writing using a high-power carbon dioxide (CO2) laser to simultaneously carbonize and pattern a spin-coated black SU-8 film. Due to the high absorption of carbon blacks in black SU-8, the laser-irradiated SU-8 surface was directly exfoliated and carbonized by a fast photo-thermal reaction. Facile laser pyrolysis of black SU-8 provides a hierarchically macroporous, graphitic carbon structure with fewer defects (ID/IG = 0.19). The experimental conditions of CO2 direct laser writing were optimized to fabricate high-quality LPCs for MSC electrodes with low sheet resistance and good porosity. A typical MSC based on an LPC electrode showed a large areal capacitance of 1.26 mF cm-2 at a scan rate of 5 mV/s, outperforming most MSCs based on thermally pyrolyzed carbon. In addition, the results revealed that the high-resolution electrode pattern in the same footprint as that of the LPC-MSCs significantly affected the rate performance of the MSCs. Consequently, the proposed laser pyrolysis technique using black SU-8 provided simple and facile fabrication of porous, graphitic carbon electrodes for high-performance on-chip MSCs without high-temperature thermal pyrolysis.

System for Fabrication of Large-Area Roll Molds by Step-and-Repeat Liquid Transfer Imprint Lithography.

The effective production of nanopatterned films generally requires a nanopatterned roll mold with a large area. We report on a novel system to fabricate large-area roll molds by recombination of smaller patterned areas in a step-and-repeat imprint lithography process. The process is accomplished in a method similar to liquid transfer imprint lithography (LTIL). The stamp roll with a smaller area takes up the liquid resist by splitting from a donor substrate or a donor roll. The resist is then transferred from a stamp roll to an acceptor roll and stitched together in a longitudinal and, if necessary, in a circumferential direction. During transfer, the nanostructured resist is UV-exposed and crosslinked directly on the acceptor roll. The acceptor roll with the stitched and recombined stamp patterns is ready to be used as a large-area roll mold for roll-based imprinting. A system for this purpose was designed, and its operation was demonstrated taking the example of an acceptor roll of 1 m length and 250 mm diameter, which was covered by 56 patterned areas. Such a system represents an elegant and efficient tool to recombine small patterned areas directly on a large roll mold and opens the way for large-area roll-based processing.

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.

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.

X Y parallel compliant stage with compact configuration.

This paper presents a piezo-driven compliant stage for nano positioning with two degree-of-freedom parallel linear motions. Nano positioning is one of the most important factors in completion of nanotechnologies. It can be accomplished by flexure-based compliant stages driven by piezo-actuators. For compact configuration, the compliant stage is stacked by two-layered compliant mechanisms. The upper layer contains a motion guide mechanism, and the lower layer two displacement amplification mechanisms. The motion guide mechanism consists of four prismatic-prismatic parallel compliant joint chains for two translational motion guides. The displacement amplification mechanism is adopted by a flexure-based flextensional amplification mechanism driven by a stack-type piezo actuator. Due to the parallel compliant joint chains, the stage has the same dynamics in the x and y axes. In this study, through design and analysis, the mechanisms were machined via wire electro-discharge machining and are were then integrated with two stack-type piezoelectric elements for actuation, and two capacitive sensors for ultra-precision displacement measurement. Finally, experiments were carried out to demonstrate the performance of the compliant stage.

Replication of a thin polydimethylsiloxane stamp and its application to dual-nanoimprint lithography for 3D hybrid nano/micropatterns.

This paper presents the fabrication of a thin and flexible polydimethylsiloxane (PDMS) stamp with a thickness of a few tens of um and its application to nanoimprint lithography (NIL). The PDMS material generally has a low elastic modulus and high adhesive characteristics. Therefore, after being treated, the thin PDMS stamp is easily deformed and torn, adhering to itself and other materials. This paper introduces the use of a metal ring around the flange of a thin PDMS stamp to assist with the handling of this material. A PDMS stamp with a motheye pattern in nanometer scale was inserted between a substrate and a microstamp with concave patterns in micrometer scale. Subsequently, three-dimensional (3D) hybrid nano/micropatterns were fabricated by pressing these two stamps and curing the resist. The fabricated hybrid patterns were measured and verified in both the microscale and nanoscale. The process, termed "dual NIL," can be applied to the fabrication of optical components or bio-sensors that require repetitive nanopatterns on micropatterns.

Driving mechanism, design, fabrication process, and experiments of a cylindrical ultrasonic linear microactuator.

A new type of cylindrical ultrasonic linear microactuator (CULMA) is introduced. The traveling wave generation condition in the stator is presented, which was confirmed using simulation and experimentation. The design and fabrication process to develop the stator is described. The stator was successfully fabricated using metallic glass and a sputtering method, and the vibration of the prototype matched the simulation results. When the driving frequency is at 626 kHz, the traveling wave in the stator was observed. Loaded with a pipe slider, the slider movement was experimentally demonstrated and the motion measured with 26 mm/s in peak speed. This paper presents a traveling wave generation method in a CULMA which would also available in other microactuators or MEMS-scale ones.