Fabricating multilevel SU-8 structures in a single photolithographic step using colored masking patterns

Abstract

The fabrication of multilevel SU-8 structures using a single photolithographic masking step is described. Preliminary data are presented on the use of photolithographic masks, containing millimeter-scale colored patterns, printed on transparent films using a standard color laser printer. The different colors printed on the photomask are shown to have differences in their UV absorptions, and hence different structure levels can be achieved from a single exposure. This method eliminates the pixelation problems encountered when using gray-scale masks (without employing photoreduction techniques) generated using a black-and-white laser printer. For research applications requiring rapid prototyping and fast turnaround times for large-scale features, this technique offers a cost-effective and time-efficient alternative to current three-dimensional lithography methods, which typically make use of multiple binary masks, alignment procedures, and exposures. Future applications will include the fabrication of textured PDMS surfaces and PDMS microfluidic substrates, cast from SU-8 molds processed using this technique.

Novel Tactile Sensor Technology and Smart Tactile Sensing Systems: A Review

“…Some recently developed 3D fabrication technologies can greatly simplify the fabrication process for tactile sensors. A typical example is the lithography based polymer MEMS fabrication technology [ 67 , 91 , 92 , 93 , 94 , 95 ]. Using cross-linkable epoxy negative permanent photoresist, high resolution and rapid micro-3D fabrications can be implemented by tuning the exposure dose emitted towards the photoresist to partially trigger post exposure cross-linking.…”

SU-8 Photolithography as a Toolbox for Carbon MEMS

“…A number of techniques have been used to implement grayscale photolithography; for example, magnetron sputtering of amorphous carbon (a-C) onto a quartz substrate where transmittance can be tailored by controlling the carbon film thickness within 0-200 nm with subnanometer precision [34]; high energy beam sensitive (HEBS) glass, which turns dark upon exposure to an electron beam, has also been used to fabricate grayscale masks: the higher the electron dosage, the darker the glass turns [35]. Yet another approach is the use of colored masks as demonstrated by Taff and colleagues [36], where they first characterized the UV absorption of different colors and then printed them on transparent film using a standard laser color printer. Other approaches include moving mask lithography [37], tilting and rotation of the substrate stage [38]; holography [39,40] and stereolithography [41].…”

Fabrication of monolithic 3D micro-systems

“…SU-8 (10) and the mixture of SU-8(50) and S1818(SU-8(50)/ S1818) were the photoresists used for the fabrication of 3D microstructures in this work.…”

“…6 Other methods used to create 3D microstructures employ gray-scale microfluidic photomasks, 9 printed color masks, 10 binary gray-level physical masks 11 and multiphoton absorption polymerization. 12 Alternatively, microscope projection lithography systems (MPLS), 5,13 which use patterned illumination controlled by digital micromirror devices (DMD), [14][15][16][17][18] offer affordable, versatile and direct conversion of computer designs into polymer microstructures, although the complexity of the 3D structuring is more restricted, and typically dedicated to positive geometries of single layers 14 and PDMS replica 19 templates.…”