The viscosity deviation of magnetic fluids for microactuator due to temperature changes

Experiments were performed to investigate the characteristics of magnetic fluids on a micro scale for the purpose of applications to a micro pump, which is the core device of Lab on a chip in medicine and biology. This work took an advantage of the phenomenon that the viscosity of a magnetic fluid decreases sharply as the temperature increases gradually. The magnetic fluid flowing through a trapezoidal silicon microchannel was heated below the temperature at which the magnetism in the magnetic fluid is not lost. As the temperature increases, the magnetic fluid became less viscid. This in turn made the pressure drop in the microchannel. Thus, this pressure drop of the heated magnetic fluid and the corresponding temperature were measured. The microchannel was fabricated by MEMS technology. Since the sheet resistance is as high as 10.6 muOmega, platinum was selected as the material of the folded film heater with the length and the thickness of 7.26 cm and 1000 Angstrom on Pyrex glass, respectively. At a proper temperature, if a magnetic fluid is applied to the magnetic field and its viscosity decreases, the response time and the net unidirectional flow of actuators such as a micro pump are expected to be improved.