Micronit Microfluidics uses glass, fused silica, silicon and plastics as material for its products. The choice of material depends on the function of the part. For instance a chip acn be made with a functional part of glass for a high quality test but with a plastic cartridge to allow handling and chip indentification.
Glass has many advantages in relation to other materials: glass is chemically inert, hydrophilic and optically clear for instance. Glass thicknesses down to 30µm can be handled.
Borosilicate glass is a very commonly used glass type. It can resist strong acids, saline solutions, chlorine, bromine, iodine and strong oxidizing and corrosive chemicals. Even for a longer period of time and at temperatures above 100 ˚C it exceeds the chemical inertness of most metals and other materials.
Borosilicate glass is mass produced, and therefore not expensive. It is available in many different thicknesses.
Fused Silica or Synthetic Quartz
For certain optical applications, borosilicate glass does not have the optimal specifications. Using fused silica chips can then offer a solution. The main advantages of fused silica are its transparency in the UV regime, its low autofluorescence, and its resistance to high temperatures.
Fused silica is often confused with quartz. But whereas quartz is a crystalline material, fused silica is amorphous, just like other glass types. Fused silica has excellent optical properties and an uniform chemical consistence.
In the graph above, the typical transmittance of borosilicate and fused silica are plotted as a function of the wavelength (click on the image to enlarge). Fused silica has a high optical transmittance, even with low wavelengths. It can be used in applications with a wavelength down to approximately 190 nm. For comparison, most borosilicate glass types are transparent down to 350 nm. Fused silica is the best material for applications that require UV transmittance or need low autofluoresence.
Micronit can handle and process glass sheets down to 30 µm thickness.
Thin glass is especially suited as a cover layer for microfluidic chips. The main use is in applications using confocal microscopy, but other applications requiring fast heating/cooling or low absorption of light or x-ray radiation could also benefit from thin glass layers.
Confocal Microscopy offers many advantages over conventional optical microscopy. The rejection of out-of-focus information leads to better imaging and a better resolution; moreover it gives the ability to have a controllable depth of field. As the light source is localised, background noise will be eliminated.
When using a confocal microscope with glass microfluidic chips it is thus important that the chips have a thin bottom layer. Micronit can integrate this thin bottom layer. Typical glass thicknesses for these applications are 145µm or 170µm.