Grayscale lithography—automated mask generation for complex three-dimensional topography

Rapid assembly of multilayer microfluidic structures via 3D-printed transfer molding and bonding

“…Although rounded channels are beneficial for some microfluidic applications, few groups have developed appropriate fabrication techniques (Supplementary Material S3.4) [8][9][10] because multilevel soft lithography has historically required multiple photolithography steps 11 . Although "grayscale lithography"-whereby resists are exposed to non-binary shades of gray-can potentially generate rounded microfluidic channels [12][13][14] , the process still requires multiple exposures to obtain larger aspect ratios 15,16 . Furthermore, although multilayer PDMS-manufacturing techniques have been demonstrated by several groups 17,18 , these are even more time-consuming and labor-intensive, requiring multiple lithography steps and precision alignment, issues that are only partially addressed by dedicated PDMS-alignment tools 19 .…”

Strategies and techniques for fabricating MEMS bistable thermal actuators.

“…The concept of grayscale lithography has been around for a while, but it is a relatively underutilized process. The unique advantage of grayscale lithography is that it allows one to theoretically produce an infinite number of three-dimensional structures in photoresist using a single step [50]. As opposed to standard binary lithography (where the photoresist film is either completely exposed or completely shielded from the ultraviolet (UV) illumination), grayscale lithography allows one to modulate the UV intensity spatially, resulting in partial photoresist exposure and development.…”

“…In more complex structures, however, such as those shown inFigure 3.17, manual creation of mask files is not feasible. Furthermore, if many iterations of a design are desired, an automatic mask generation technique is important[50]. This requires the development of a fast automated process for producing mask files with complex 3D surface geometry.…”

“…We believe the discontinuities in the surface profile as shown inFigure 3.24 (b) may be a result of stitching errors from neighboring passes of the laser interfering with each other and either overexposing or underexposing portions of the photoresist during the writing process (and not due to non-linearity of the photoresist) 24. (a) Uncalibrated Dekak profile for the inverted dome structure[50]. (b)…”

“…Dektak profilometer of the dome structure after thermal reflow[50]. of this research is to design, fabricate, and test a bistable MEMS buckled diaphragm which will change its state (buckled up/down) upon the application of a set temperature.…”