This paper presents an experimental investigation on the thermal performance of a micro pulsating heat pipe (MPHP)embedded on a silicon wafer with the trapezoidal cross section having a hydraulic diameter of 352 μm. With FC-72 and R113 as working fluids

the effects of gravity

filling ratio

and working fluid on the thermal performance of MPHP are discussed. Experimental results show that the MPHP functions well at its hydraulic diameter or a Bond number about 0.45. Gravitational effect on the thermal performance cannot be ignored although it is small in comparison with the surface tension effect. At an inclination angle larger than 10°

the MPHP works as a true pulsating device when the filling ratio varies from 30% to 65%

enhancing the heat transfer capacity effectively. For FC-72 and R113

the optimal filling ratio is 55% and 41%

respectively

for the best thermal performance of the MPHP. The heat transfer capability of the MPHP is significantly enhanced and the thermal resistances is reduced up to about 56. 5% (FC-72)and 59. 7% (R113)at a power input of 8.5 W with the corresponding optimal filling ratios when compared to the unfilled MPHP(0 filling ratio).It is also found that R113 is fit for the MPHP at lower heat loads

while FC-72 is favorable at relatively higher heat loads.