We focused on the fact that the color of blood changes from bright red to dark red when coagulation occurs in a circuit, and investigated the possibility of detecting coagulation in circuits from changes in light absorbance before and after coagulation.When the calcium chloride was added, a sharp drop in optical power was seen, and optical power subsequently continued to gradually decrease as coagulation progressed. After blood coagulation had ended and the roller pump was stopped, we saw that optical power gradually recovered. In general, a similar change was seen for the optical sensors at each wavelength. However, if the ratio of optical power before and after coagulation is taken as the change in absorbance, we realized that, because the results differed for different wavelengths, an optimum wavelength exists for detecting changes in absorbance before and after coagulation.
