| Summary: | Three-dimensional (3D) microstructures can enhance the optical, electrical and
mechanical properties of the microfluidic system. However, the 3D microfabrication
is challenging when simultaneous control over fabrication of lateral and vertical
dimensions is required. To achieve such control, grayscale photolithography
technique has been comprehensively studied as an alternative to the current 3D
microfabrication technique. Current techniques require highly sophisticated and
PTTA
expensive equipments, with slow point-to-point or layer-by-layer approach of pattern
exposure. The proposed grayscale photolithography technique in this research has
been used in realization of microstructures with height between 163.8 µm and 1108.7
µm in a single exposure through grayscale photomask. The grayscale
photolithography technique developed in this study has been applied for realization
of 3D microstructures in fiber optic-based refractive index sensor, PDMS surface
wettability modification and passive micromixers. The fabrication of fiber optic-
based refractive index sensor has been improved by providing a 3D microfluidic
environment to help float the fiber optic inside the microchannel. High sensitivity of
1509.3 nm/RIU was achieved for refractive index sensing of different Sodium
Chloride solution concentrations. Fabrication of micro curvature structures on PDMS
surface has increase its wettability into superhydrophobic state with water contact
angle 157.3 °. Various shapes and designs of micromixers, including the different
height of obstacles inside the microchannel have been fabricated and achieve a good
mixing performance. In sum, a 3D microfabrication by grayscale photolithography technique has been developed, with functional applicability for fabrication of several
microfluidic functions.
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