Hybrid Organic-Inorganic photoresists, a promising class of materials for Optofluidic integration

Abstract

Through the efforts to fuse planar optics and microfluidics in order to produce dye lasers, biosensors, trapping and cell sorting device, we can notice the rising interest in optofluidics since early and mid 2000's. However mass production of these devices heavily relies on fast and easy patterning of the constituent material. PDMS, being one of these materials, gained an added value because of its elasticity, hydrophobicity and permeability to gaz. Nonetheless, these specifications are not convenient for all types of applications. The growing capability to use Hybrid Organic-Inorganic materials for the fabrication of integrated optics components and microfluidic channels is what makes this class of materials an ideal candidate for this integration. This work aims to implement, on the same chip, an optical and a microfluidic layer using Sol-Gel processing of Organic-Inorganic materials. The interest in this vertical integration arises from the need to manipulate the fluid in the microchannels using evanescent field optical pressure.

Recent Advances in Positive Photoresists: Mechanisms and Fabrication

“…The inorganic constituent enhances the photosensitivity because of its higher tendency to absorb EUV light, strengthens the mechanical structure, leading to reduced pattern collapse, and provides better etch-resistance, hence, allowing for higher aspect ratios [ 32 ]. The organic component governs the elastic and ductile properties of the photoresist, allowing for crack-free coatings [ 33 ] and a change in solubility properties of the photoresist during development conditions.…”

Development and Characterisation of a Whole Hybrid Sol-Gel Optofluidic Platform for Biosensing Applications

“…Deformation of microchannels can occur due to solvent induced swelling [ 28 ]. The inherent hydrophobic nature of PDMS can also pose problems for the control of fluids, in particular towards biosensing and biomedical applications [ 29 , 30 ]. Various contact angle measurements have been reported for untreated PDMS ranging from 105° to 113.5° [ 31 , 32 ].…”

“…Due to the hybrid character of these family of materials and their inherent liquid nature, they can be processed as thin films and further photostructured as microstructures, of great interest for the fabrication of miniature multifunctional devices. One of the recently reported concepts consists of exploiting photoreactive hybrid sol-gel materials for the parallel and direct fabrication of both systems onto the same substrate employing a standard photolithography process [ 29 ]. Hybrid sol-gel materials are attractive materials to use as dual fabrication materials owing to their increased chemical and mechanical properties which can be attributed to the inorganic–organic hybrid nature of the material [ 34 ].…”

“…These materials have shown promise towards a variety of sensing applications, including optical sensors for O 2 [ 37 , 38 ] and water vapour sensing [ 39 ], and in photonic sensors for the detection of biofilm formation [ 40 ]. As negative photoresists they eliminate the need for a master mould to be used and, therefore, are suitable for low cost production of optofluidic or microfluidic devices [ 29 ].…”