Lithography

About: Lithography is a research topic. Over the lifetime, 23507 publications have been published within this topic receiving 348321 citations.

3D printing of conducting polymers.

Abstract: Conducting polymers are promising material candidates in diverse applications including energy storage, flexible electronics, and bioelectronics. However, the fabrication of conducting polymers has mostly relied on conventional approaches such as ink-jet printing, screen printing, and electron-beam lithography, whose limitations have hampered rapid innovations and broad applications of conducting polymers. Here we introduce a high-performance 3D printable conducting polymer ink based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) for 3D printing of conducting polymers. The resultant superior printability enables facile fabrication of conducting polymers into high resolution and high aspect ratio microstructures, which can be integrated with other materials such as insulating elastomers via multi-material 3D printing. The 3D-printed conducting polymers can also be converted into highly conductive and soft hydrogel microstructures. We further demonstrate fast and streamlined fabrications of various conducting polymer devices, such as a soft neural probe capable of in vivo single-unit recording.

Etching and narrowing of graphene from the edges

Abstract: Large-scale graphene electronics requires lithographic patterning of narrow graphene nanoribbons for device integration. However, conventional lithography can only reliably pattern approximately 20-nm-wide GNR arrays limited by lithography resolution, while sub-5-nm GNRs are desirable for high on/off ratio field-effect transistors at room temperature. Here, we devised a gas phase chemical approach to etch graphene from the edges without damaging its basal plane. The reaction involved high temperature oxidation of graphene in a slightly reducing environment in the presence of ammonia to afford controlled etch rate (less than or approximately 1 nm min(-1)). We fabricated approximately 20-30-nm-wide graphene nanoribbon arrays lithographically, and used the gas phase etching chemistry to narrow the ribbons down to <10 nm. For the first time, a high on/off ratio up to approximately 10(4) was achieved at room temperature for field-effect transistors built with sub-5-nm-wide graphene nanoribbon semiconductors derived from lithographic patterning and narrowing. Our controlled etching method opens up a chemical way to control the size of various graphene nano-structures beyond the capability of top-down lithography.

Stop-flow lithography in a microfluidic device

Abstract: Polymeric particles in custom designed geometries and with tunable chemical anisotropy are expected to enable a variety of new technologies in diverse areas such as photonics, diagnostics and functional materials. We present a simple, high throughput and high resolution microfluidic method to synthesize such polymeric particles. Building off earlier work that we have done on continuous flow lithography (CFL) (D. Dendukuri, D. C. Pregibon, J. Collins, T. A. Hatton, P. S. Doyle, Nat. Mater., 2006, 5, 365–369; ref. 1), we have devised and implemented a new setup that uses compressed air driven flows in preference to syringe pumps to synthesize particles using a technique that we call stop-flow lithography (SFL). A flowing stream of oligomer is stopped before polymerizing an array of particles into it, providing for much improved resolution over particles synthesized in flow. The formed particles are then flushed out at high flow rates before the cycle of stop-polymerize-flow is repeated. The high flow rates enable orders-of-magnitude improvements in particle throughput over CFL. However, the deformation of the PDMS elastomer due to the imposed pressure restricts how quickly the flow can be stopped before each polymerization event. We have developed a simple model that captures the dependence of the time required to stop the flow on geometric parameters such as the height, length and width of the microchannel, as well as on the externally imposed pressure. Further, we show that SFL proves to be superior to CFL even for the synthesis of chemically anisotropic particles with sharp interfaces between distinct sections.

Micromachining applications of a high resolution ultrathick photoresist

Abstract: This article describes a new negative‐tone photoresist, SU‐8, for ultrathick layer applications. An aspect ratio of 10:1 has been achieved using near‐ultraviolet lithography in a 200‐μm‐thick layer. The use of this resist for building tall micromechanical structures by deep silicon reactive‐ion etching and electroplating is demonstrated. Using SU‐8 stencils, etched depths of ≳200 μm in Si and electroplated 130‐μm‐thick Au structures with near‐vertical sidewalls have been achieved.

Soft lithographic methods for nano-fabrication

Abstract: Soft lithography is a low-cost, non-photolithographic strategy for carrying out micro- and nano-fabrication This unconventional approach consists of techniques based on self-assembly and replica molding of organic molecules and polymeric materials Four such techniques, microcontact printing (µCP), replica molding, micromolding in capillaries (MIMIC), and microtransfer molding (µTM), have been demonstrated for the fabrication of patterns and structures of a variety of materials with dimension ≥30 nm This review describes these techniques and their applications in fabrication and manufacturing at the sub-100 nm scale