Selective laser etching (SLE) is a technique that allows the fabrication of arbitrarily shaped glass micro-objects. In this work, we show how the capabilities of this technology can be improved in terms of selectivity and etch rate by applying an etchant solution based on a Potassium Hydroxide, water, and isopropanol mixture. By varying the concentrations of these constituents, the wetting properties, as well as the chemical reaction of fused silica etching, can be changed, allowing us to achieve etching rates in modified fused silica up to 820 μm/h and selectivity up to ∼3000. This is used to produce a high aspect ratio (up to 1:1000), straight and spiral microfluidic channels which are embedded inside a volume of glass. Complex 3D glass micro-structures are also demonstrated.
Nowadays, lab-on-chip (LOC) devices are attracting more and more attention since they show vast prospects for various biomedical applications. Usually, an LOC is a small device that serves a single laboratory function. LOCs show massive potential for organ-on-chip (OOC) device manufacturing since they could allow for research on the avoidance of various diseases or the avoidance of drug testing on animals or humans. However, this technology is still under development. The dominant technique for the fabrication of such devices is molding, which is very attractive and efficient for mass production, but has many drawbacks for prototyping. This article suggests a femtosecond laser microprocessing technique for the prototyping of an OOC-type device—a liver-on-chip. We demonstrate the production of liver-on-chip devices out of glass by using femtosecond laser-based selective laser etching (SLE) and laser welding techniques. The fabricated device was tested with HepG2(GS) liver cancer cells. During the test, HepG2(GS) cells proliferated in the chip, thus showing the potential of the suggested technique for further OOC development.
Purpose: To create a fast, affordable, reproducible a liver-on-a chip platform as an alternative to animal models of liver diseases. Methods: The platform was fabricated out of fused silica by using femtosecond laser microprocessing. A channel with integrated filters of micropillars was produced by Selective Laser Etching (SLE) technique. Nano gratings were inscribed inside the glass by using focused femtosecond laser radiation. Subsequently, liver cells were etched in 35% Potassium Hydroxide (KOH) at 90 ° C or Hydrofluoric acid. The contact between both plates was achieved by intense light radiation with an integrated filter. There were 700 fs duration pulses used for SLE and 200 fs for laser welding. The light was focused with a 20 x 0.45 NA objective for SLE and a 0.5 NA aspherical lens for laser welding. The human liver HCC cell line HepG2(GS) was employed for biocompatibility testing. Results: The platform consists of one channel divided into three sub channels by micropillars: the central channel for cells and two side channels for cell medium. All channels have inlet and outlet reservoirs with the depth up to 200 μm, and width of central and side channels up to 200 and 400 μm, respectively. Additionally, the final size of micropillars was 55 x 36 μm with a gap of 14 μm in between. Conclusion: Based on our previously published work, this study provides a step-by-step design and validates the concept of testing human liver cancer cells. In addition, it provides developmental advancements and drawbacks of liver-on-a-chip designs.
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