Transparent thin thermoplastic biochip by injection-moulding and laser transmission welding

Recently microfluidic devices have emerged as a viable technology for the miniaturization of high throughput tools for analytical tasks related to structural biology such as screening of crystallization conditions and structural analysis. This work reports the manufacture of microfluidic chips in transparent thermoplastic polymers [poly(methylmethacrylate) (PMMA), and cyclic olefin copolymer (COC)] using two complementary technologies, injection moulding for the fabrication of the fluidic level and laser transmission welding for the sealing of the cover. A steel mould insert was produced by laser micro caving using a solid state laser radiation source (Nd:YAG, wavelength 1,064 nm). Fluidic chips of ~670 μm thickness comprising channels of 50 μm depth and width down to 50 μm were injection moulded in PMMA and COC. Joining of transparent thin cover film to the micro-injected fluidic level was performed by laser transmission welding using high power diode laser radiation (wavelength 940 nm) and an intermediate thin absorbing layer with a thickness of about several nanometers.