Three‐dimensional femtosecond laser micromachining of photosensitive glass for biomicrochips

Abstract

Internal modification of transparent materials such as glass can be carried out using multiphoton absorption induced by a femtosecond (fs) laser. The fs-laser modification followed by thermal treatment and successive chemical wet etching in a hydrofluoric (HF) acid solution forms three-dimensional (3D) hollow microstructures embedded in photosensitive glass. This technique is a powerful method for directly fabricating 3D microfluidic structures inside a photosensitive glass microchip. We used fabricated microchips, referred to as a nanoaquarium, for dynamic observations of living microorganisms. In addition, the present technique can also be used to form microoptical components such as micromirrors and microlenses inside the photosensitive glass, since the fabricated structures have optically flat surfaces. The integration of microfluidics and microoptical components in a single glass chip yields biophotonic microchips, in other words, optofluidics, which provide high sensitivity in absorption and fluorescence measurements of small volumes of liquid samples.Dynamic observation of microorganisms (Euglena gracilis) using nanoaquarium, which has 3D microfluidic structure, fabricated in a photosensitive glass microchip by femtosecond laser direct writing followed by thermal treatment and successive wet chemical etching.

In-channel integration of designable microoptical devices using flat scaffold-supported femtosecond-laser microfabrication for coupling-free optofluidic cell counting

“…A 3D embedded glass microchannel with high surface smoothness was prepared in a commercially available photosensitive Foturan glass (from Mikroglas, Langen (Hessen), Germany) by FLAE. [21][22][23] The glass microchannel was filled with the epoxy-based negative-type resin SU-8 (2075; MicroChem, Newton, America), which is widely used for FSS-HFLM fabrication ( Supplementary Fig. S1).…”

“…Our group has reported a series of studies on the fabrication of 3D embedded glass microchannels using femtosecond laser-assisted etching (FLAE). [21][22][23] The surface smoothness of the microchannels was improved by smaller-pitch line-to-line scanning and optimized postthermal annealing. To enhance their functionalities, some 1D to 3D glass microcomponents, including waveguides, [24][25][26] microrotators, 27 micromirrors, 23 and microlenses, 28 have been integrated into the channels.…”

Progress in ultrafast laser processing and future prospects

“…12(a)). This two-step procedure results in the formation of 3D microfluidic structures inside glass such as photosensitive glass [96,98,99] and fused silica [84,100]. The microchannels fabricated by FLAE inevitably become wider than the laser-exposed regions and are tapered because of an etch selectivity ratio of approximately 50 between the laser-exposed and laser-unexposed regions.…”

Ship-in-a-Bottle Biomicrochips Fabricated by Hybrid Femtosecond Laser Processing

“…This technique can also integrate some kinds of microoptical components and fluid control microcomponents. Then, this technique was successfully applied to fabricate functional microfluidics and optofluidics for determining the functions of microorganisms [2,[4][5][6]. In the meanwhile, this technique is somewhat weak in integrating complex microcomponents with micro and nano feature sizes in the microfluidics due to its limited spatial resolution and top-down processing nature.…”