Bubble Nucleation and Behavior on Micro Square Heaters

Abstract

In this study, micro square polysilicon heaters having dimensions of 65 × 65 μm² and 100 × 100 μm² were fabricated on a silicon dioxide layer, and bubble nucleation experiments on the heaters were performed. Bubble nucleation temperature was measured using a bridge circuit, and the photographs of bubble nucleation and subsequent growth were taken by a 35-mm camera with a μs flash unit. Measured bubble nucleation temperatures were found to be closer to the superheat limit of the working fluid of FC-72. A quasi-1-D solution obtained from the 2-D heat diffusion equation yielded proper temperature distribution of the square heaters at steady state; however, it failed to predict the temperature rise up to the steady state. The time-dependent temperatures similar to the observed values can be obtained with much lower value of thermal diffusivity than the bulk property of the polysilicon heater used. For the 100 × 100 μm² square heater, nucleation of several bubbles was observed, but for the 65 × 65 μm² heater, only that of one bubble was observed.

This work was supported by the Korea Research Foundation Grant (KRF-2003-041-D00114).

This paper was presented at the Micro/Nanoscale Energy Conversion Transport 2004, August 9–12 at Inje University, Korea.

Keywords:

• bubble nucleation
• micro square heater
• temperature distribution

Notes

This work was supported by the Korea Research Foundation Grant (KRF-2003-041-D00114).

This paper was presented at the Micro/Nanoscale Energy Conversion Transport 2004, August 9–12 at Inje University, Korea.