We have developed a new type of non-contact three-dimensional photo-thermal etching method for agar microculture chips exploiting the characteristics of two different wavelengths of infrared laser beams. We used two different wavelengths of infrared (1480 and 1064 nm) focused laser beam as a heat source to melt and remove a portion of 200 μm high agar gel layer on the 5 nm thick chromium-coated glass slide. As the 1480 nm infrared beam is absorbed by water, the agar gel on the light pathway is heated and melted. On the other hand, as the 1064 nm infrared beam is not absorbed by water and agar, the melting of the agar occurred just near the chromium thin layer that absorbs 1064 nm infrared light. Using this non-contact etching, we can easily make microstructures in agar-layer using infrared laser beam only within a few minutes; i.e. cell-culture holes are melted by 100 mW, 1480 nm laser and tunnels by 100 μm/s, 40 mW, 1064 nm laser, respectively. The size of holes and tunnels were also controlled by choosing the irradiation power and time of infrared lasers. Those results indicate that we can make and use microstructures for biological use without any expensive microfablication facilities nor a series of complicated procedure and time.
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