Liquid metal-based reconfigurable and stretchable photolithography

Abstract

Conventional ultraviolet (UV) lithography typically uses a photomask made of a fused silica plate covered with a layer of UV opaque material such as chromium. The photomask has passive binary patterns of UV opaque and UV transparent regions and the pattern is unalterable. We report a novel real-time dynamically reconfigurable photomask technology using a liquid metal (as a UV opaque material) filled in polydimethylsiloxane (PDMS, as a UV transparent material) microfluidic channels. We found that the gallium-based liquid metal (e.g. Galinstan ® ) is opaque in broad spectrum of light in the wavelength from 325 nm to 850 nm while the PDMS is highly transparent in this wide range of spectrum. We made both bright field and dark field microfluidic photomasks and transferred various patterns onto a positive photoresist. A 7-segment display microfluidic channel photomask was also fabricated and decimal numerals (from '0' to '9') were patterned with one photomask by dynamically reconfiguring decimal numeral shapes with on-demand injection and withdrawal of the liquid metal in specific segment microfluidic channels in the photomask. In addition, utilizing mechanical flexibility of the PDMS and the liquid metal, reconfiguration of the patterns in a microfluidic photomask under stretching was successfully tested.

Magnetic Liquid Metals: A Review

“…There have been numerous methods developed to pattern LMs including imprinting, [ 120 ] stencil mask‐based lithography, [ 121 ] injection into microfluidic channels, [ 122 ] vacuum filling, [ 123 ] direct laser patterning, [ 124 ] etc. While most of the patterns demonstrated were hundreds of micrometers or millimeters in size, there has been a recent demonstration of LM patterning of sub‐micron (down to 500 nm) features on elastomer using a stamping process through an electron beam lithography patterned photoresist.…”

Soft Multifunctional Composites and Emulsions with Liquid Metals

“…The focus of these articles range from circuit and sensing applications to emerging fabrication methods based on lithographic, additive, subtractive, and injection‐based techniques . More recent developments in LM microfluidics have been directed towards 3D printing of microfluidic channels and applications of LM in antennas and resonators, electrodes and metamaterials . In addition, there has been an increased focus on exploring different phenomena like electro‐chemistry, wettability, and interfaces of LMs.…”

Soft-Matter Printed Circuit Board with UV Laser Micropatterning

“…This oxidation and moldability has enabled EGaIn to be patterned with a variety of techniques , based on stencil lithography, , selective wetting, , reductive patterning, microcontact printing, ,− jetting, and 3D direct-write printing. − Since the mid 2000s, EGaIn microfluidic systems have been engineered for a broad range of applications. , In the last couple of years, this includes continued efforts in sensing and electromechanical transducers, − force characterization for medical endoscopy, reconfigurable metamaterials, , and radio antennae that exhibit tunable operating frequency and enhanced range. − …”