Fig. 3.

Thermal response of device. (A) Thermopile response to local electrical heater. A step function of electrical power (4.0 μW) is applied beginning at t = 0. A vacuum of 2 mtorr is maintained, and the device reaction chamber is filled with water. (B) Simulation of thermal response under heat generation inside the chamber at 1 μW. The measurement chamber is the circle. The six U-turn lines are the metallic sensors, and the four rectangles are fluidic channels. (C) Experimental data of thermal conductance, G, of the device under vacuum at different pressures. The fitting formula is G(p) = G_res + G_air/(1 + $\frac{171}{pd}$), where p is the vacuum chamber pressure (in torr). The fitting parameters are residual thermal conductance (caused by parylene, etc.) G_res = 15.5 μW/K, the thermal conductance of air at 1 atm G_air = 214 μW/K, and a geometric factor d = 170 μm. The geometric factor d is related to the thickness of the vacuum jacket and the size of the measurement chamber.