DISPOSABLE AIR-BURSTING DETONATORS AS AN ALTERNATIVE ON-CHIP POWER SOURCE Chien-Chong Hong, Jin-Woo Choi, and Chong H. Ahn Microsystems and BioMEMS Lab Department of Electrical and Computer Engineering and Computer Science University of Cincinnati Cincinnati, OH 45221-0030, USA ABSTRACT A new concept of disposable air-bursting detonator as an alternative on-chip power source has been proposed, designed, and successfully demonstrated in this paper for disposable lab-on-a-chips or biochips. In this new disposable air-bursting detonator, a microheater is positioned on the thermoplastic membrane attached over a pressurized chamber. By applying an electrical pulse into the microheater, the thermoplastic membrane can be broken and then the pressurized air will be detonated to drive liquid samples through microchannels. Both air pressure and detonating temperature are adjustable to get desired driving pressure responses. Dynamic pressure response of the fabricated air-bursting detonator has been simulated and experimentally characterized. Due to its compact structure and fast response, this detonator will be a promising alternative power source to drive fluid samples in disposable lab-on-a-chips or portable clinical diagnostic kits. INTRODUCTION Micropumps are the most common devices to produce and control pressure for microfluidic systems. There have been many reports for the development of active micropumps using electrostatic, electromagnetic, thermo- pneumatic, electrohydrodynamic or magnetohydrodynamic actuation [1-6]. However, the active micropumps usually require on-line electrical power or off-line batteries. For disposable microfluidic-based biochips or biochemical detection systems, however, the active micropumps should be integrated with disposable batteries, which increases the cost and also involves many technical difficulties. So, an alternative new power source to the battery is desirable for the disposable biochips or clinical diagnostic kits, combining with passive-type microfluidic components. Micro gas-turbine engine could be a possible option to provide fast-response pressure source for driving liquid in a microchannel, but they are not suitable for the microfluidic biochips due to its environmental noises such as humidity, shock, and vibration [7-9]. Other option could be a cold- gas microthruster, which consists of a nozzle structure and a heater to produce pressurized gas output by heating gas. However, it also needs high power consumption in heating up gas to generate enough pressure [10]. Although mass- production would be possible with the gas microthruster, this approach is still cost-ineffective for disposable biochips or biological analysis systems. In this work, a novel concept for an alternative on-chip power source has been proposed and realized to address the problems from the disposable microfluidic biochips and biological analysis systems. Gas or air pressurized in a micro chamber can be utilized as a power source to control liquid flow on the disposable chips. The gas or air can be stored in the chamber and then detonated as shown in Figure 1 (a). (a) (b) Figure 1. Schematic illustrations of the disposable air- bursting detonator as an alternative on-chip power source for disposable biochips: (a) cross-sectional view of the device and (b) driving principle of the air-bursting detonator. Pressurized air Thermo plastic membrane Inlet port and sealing Localized heater “detonator” Air pressure applies after bursting-out Analysis unit Air-bursting detonator Liquid inlet Outlet Before Bursting Liquid inlet Outlet After Bursting Broken Gas Analysis unit Liquid inlet Liquid inlet Mixed fluids Air-bursting detonator 0-7803-7185-2/02/$10.00 ©2002 IEEE 240