Explosive Micro-Bubble Actuator

Abstract

Explosive Micro-Bubble Actuator proefschrift ter verkrijging van de graad van doctor aan de Universiteit Twente op gezag van de rector magnificus prof. dr. W.H.M. Zijm, volgens besluit van het College voor Promoties in het openbaar te verdedigen op vrijdag 31 oktober 2008 om 15:00 uur door Dennis Micha van den Broek geboren op 11 augustus 1979 te Vlaardingen Dit proefschrift is goedgekeurd door de promotor: prof. dr. M.C. Elwenspoek aan mijn vader Summary Samenvatting Dankwoord Chapter 1 Actuators and Bubbles A large variety of actuators can be found in literature. This chapter provides a brief overview of different actuator principles with a focus on thermo-pnuematic actuation and actuators, which utilize bubbles to provide the actuation force. The second part of this chapter will give a summary of the research on bubble nucleation and bubble dynamics under high heat-flux conditions. At the end of this chapter, an outline of this thesis is given.

Bubble nucleation in an explosive micro-bubble actuator

“…An actuator, which utilizes the pressure generated by explosive evaporation in a closed cavity to deflect a membrane, was developed [8]. Inside this actuator, bubbles are created by applying potential difference across a micrometer-sized heater for a few microseconds.…”

Vapor bubbles in confined geometries : a numerical study

“…Other interesting situations may be envisaged such as the micro-bubble actuator fabricated in [13]. This device consist of a liquid filled cavity with a resistive heater on the lower wall and a membrane as its top wall.…”

“…The size of this boundary 120 CHAPTER 7. VAPOR BUBBLE BETWEEN CIRCULAR DISCS layer may be approximated as δ wall = πD wall t (7.12) The heat flux from the liquid film to the glass must be the same as the energy put into the thermal boundary layer δ wall , so 13) with k l ,k w the thermal conductivities of the liquid and the glass respectively, and the other quantities as defined in figure 7.8. From this the temperature at the liquid/glass interface is obtained as From the experiments the liquid film thickness was estimated as 1 µm for all cases.…”

“…Andere interessante situaties kunnen bestudeerd worden, zoals de micro-bel actuator vervaardigd in [13]. Dit systeem bestaat uit een holte gevuld met een vloeistof.…”

“…This is certainly not the only application. Various actuators based on the fast dynamics of a vapor bubble, nucleated on an impulsively heated element, have been designed, resulting in displacements in the micrometer range and frequencies up to several kHz [12,13].…”