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.
Highlights
Soft lithography by Polydimethylsiloxane (PDMS) replica molding paved the way for rapid prototyping of microfluidic chips [1,2,3,4]
The fabrication of master molds varies from micro-milled [5] substrates over structured printed circuit boards (PCBs) [6,7] to photolithograpically obtained structures [8]
These methods compete in their minimal feature size and overall costs [9]
Summary
Soft lithography by Polydimethylsiloxane (PDMS) replica molding paved the way for rapid prototyping of microfluidic chips [1,2,3,4]. The fabrication of master molds varies from micro-milled [5] substrates over structured printed circuit boards (PCBs) [6,7] to photolithograpically obtained structures [8] These methods compete in their minimal feature size and overall costs [9]. RRoouunnddeedd cchhaannnneell ssttrruuccttuurreess wweerree aacchhiieevveedd bbyy mmooddiiffyyiinngg tthhee eexxppoossuurree ooff tthhee DDFFRR bbyy iinnsseerrttiinngg tthhee ddiiffffuusseerr eelleemmeenntt bbeettwweeeenn tthhee UUVV ssoouurrccee aanndd ssuubbssttrraattee,, tthhuuss ccrreeaattiinngg ssttaattiissttiiccaallllyy ddiissttrriibbuutteedd ssccaatttteerriinngg cceenntteerrss ffoorr tthhee iinnccoommiinngg lliigghhtt. TThhee sseettuupp ffoorr tthheebbaacckkssiiddeeeexxppoossuurreeccaannbbeeseseenenininFiFgiugruere1.1T.hTehdeifdfuifsfeurseerleemleemntewntaws paslapceladceodn otonptoopf tohfethUeVUsVousorucer,cec,ocvoevrienrgingit ictocmomplpelteetleyl.yI.nIncoconntrtarsatsttotoththeessttaannddaarrddpprroocceedduurree,, tthhee llaammiinnaatteedd ssuubbssttrraattee wwaass ppllaacceedd,, wwiitthh tthhee ggllaassss ssiiddee ffaacciinngg ttoowwaarrdd tthhee UUVV ssoouurrccee,, iinn tthhee ppaatthh ooff lliigghhtt. AA ddiissttaannccee bbeettwweeeenn tthhee UUVV ssoouurrccee aanndd pprroobbee ooff 223355 mmmm ffoorr aa hhoommooggeenneeoouuss eexxppoossuurree wwaass sseett bbyy ssppaacceerrss.
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