Rounding of Negative Dry Film Resist by Diffusive Backside Exposure Creating Rounded Channels for Pneumatic Membrane Valves

Abstract

Abstract:Processing of dry film resist is an easy, low-cost, and fast way to fabricate microfluidic structures. Currently, common processes are limited to creating solely rectangular channels. However, it has shown that rounded channels are necessary to ensure proper closing of pneumatic membrane valves for microfluidic devices. Here, we introduce a modification to the standard lithography process, in order to create rounded channels for microfluidic structures. Therefore, a diffuser element was inserted into in the optical path between the light source and glass substrate, which is then exposed through the backside, hence altering the exposure to the dry resist spatially. Characterization of the process was carried out with different exposure times, features sizes, and substrate thickness. The process modification is almost effortless and can be integrated in any lithography process.

Upscaling of pneumatic membrane valves for the integration of 3D cell cultures on chip

“…Only positive photoresists can be subjected to a reflow process. 14 However, this material property is accompanied by several limitations regarding the chemical and thermal stabilities restricting achievable channel heights to a maximum of a few tens of micrometers in traditional processes. [15][16][17] Therefore, the fabrication of replication molds for complex mLSI chip platforms that incorporate various channel heights and cross-sectional geometries is limited by the inherent material properties of available photoresists.…”

“… 16 The channel height limitation of the photolithography production method for mLSI chips has been addressed by manufacturing PDMS casting molds using e.g. backside photolithography, 14 deflection of flexible membranes, 15 or micro-milling. 12 However, design alterations, prolonged production times, and availability of high-precision mills restrict these approaches.…”

Utilizing a photosensitive dry film resist in proton beam writing

“…Microfabrication in DFRs has been employed as the master molds for fabricating poly(dimethylsiloxane)/PDMS microfluidic devices using soft-lithography. [14][15][16][17][18][19][20] Moreover, Tsai et al 21) demonstrated the applying DFR microfluidic channels in microchip capillary electrophoresis. The DFR microfluidic patterns were transferred to glass substrates by the wet etching method for microfluidic devices, as presented by Zhang et al 22) The DFR micropatterns have been manufactured by photolithography, [23][24][25] UV-LEDs (light-emitting diodes) direct writing lithography, 26) direct projection lithography, 27) reactive ion etching and laser ablation, 28) and microscopebased maskless micropatterning technique.…”

Performance Evaluation of Free-Space Fibre Optic Detection in a Lab-on-Chip for Microorganism

“…The material chosen depends on the application, physicochemical properties of the analyte, biocompatibility, and possibly integration with other devices and materials [16]. One of the approaches in LOC development is dry film resist (DFR) where it is effective, reproducible, and cheap; has a less complicated fabrication process; and is easy to handle [20].…”