Fabrication method of microfluidic circuit, and microfluidic circuit fabricated by method thereof
A fabrication method of a microfluidic circuit is provided, dispensable of mask registration, absent of deviation in mask positioning, and inexpensive in fabrication cost. The fabrication method of a microfluidic circuit has a light transmissive substrate stacked on a light absorptive substrate, and the light transmissive substrate welded with the light absorptive substrate for bonding by directing light through the light transmissive substrate. The microfluidic circuit includes a microchannel at the bottom face of the light transmissive substrate and/or at the top face of the light absorptive substrate. The method includes the step of forming, at the light transmissive substrate, a light attenuation region attenuating transmittance of light towards the microchannel when light is directed through the light transmissive substrate.
1. A fabrication method of a microfluidic circuit having a light transmissive substrate that is composed of thermoplastic resin and that is stacked on a light absorptive substrate, said microfluidic circuit including a microchannel at a bottom face of said light transmissive substrate and/or at a top face of said light absorptive substrate, said method comprising:
forming, at said light transmissive substrate, a light attenuation region attenuating an amount of light to not more than 80%, wherein said light attenuation region contains a light blocking material composed of carbon black,
after forming the light attenuation region, welding the light transmissive substrate to the light absorptive substrate by directing light through the light transmissive substrate, wherein the amount of light transmitted toward said microchannel is attenuated, by said light attenuation region, to not more than 80% of an amount of light directed to said light transmissive substrate,
wherein said light transmissive substrate has a thickness d and a refraction index n, and includes a microchannel of a width w at a bottom face, and a value of (d/w) tan [90−θ−sin −1 {(sin(90−θ))/n}] is at least 0.1, where θ is an incident angle of directed light transmitted to said microchannel.
2. The fabrication method of a microfluidic circuit according to claim 1 , wherein said light attenuation region at said light transmissive substrate includes a surface having an arithmetical mean roughness Ra of 1 μm to 50 μm.
3. The fabrication method of a microfluidic circuit according to claim 1 , wherein said light attenuation region at said light transmissive substrate includes a cavity having a face such that light directed substantially perpendicularly with respect to a top face of the light transmissive substrate does not enter perpendicularly to the face of the cavity.
4. A microfluidic circuit fabricated by the method of claim 1 .