precision microfluidic oscillators for on-chip timing and control

Professor: Cheng-Hsien, LiuStudent: Hao-Ran, Shih (9933533)

Date: 2010/12/28

Philip N. Duncan, Transon V. Nguyen and Elliot E. HuiDepartment of Biomedical Engineering, University of California, Irvine, CA, USA

OutlineABSTRACTINTRODUCTIONTHEORYEXPERIMENTALCONCLUSION

ABSTRACT1.A precision pneumatic oscillator which provides timing signals for integrated microfluidic digital logic circuits2.The design is based on the classical ring oscillator circuit and requires only a vacuum supply for power3.Integrate pneumatic and fluidic circuits to

create an autonomously driven peristaltic pump

INTRODUCTION1.Microfluidic Large-Scale-Integration has been

a highly successful technology for the automation of multiplexed chemical reactions

2.A control system built solely out of microfluidic components would be attractive because it could be manufactured in parallel with fluid-handling elements on a single chip

3.Lab-on-a-chip devices require timing to control fluid-handling elements such as peristaltic pumps must be driven by carefully coordinated waveforms

Device fabrication

THEORY

Mathies technology

IN

OUT

Vacuum Source Ground

Ring Oscillator Circuit1.The system is inherently unstable and will

thus oscillate indefinitely. (odd number )2.The frequency of oscillation should vary

linearly with 1/(pneumatic resistance ), allowing tuning of the oscillator.

EXPERIMENTAL mask layout for a 3-

inverter ring oscillator

photodiode detector Movement of the elastomeric membrane in

the valve causes a deflection of the laser beam resulting in a change in measured intensity

Frequency Design other resistances in the circuit begin to

dominate, such as the resistance of the lines connecting the 3 inverter stages

saturate

changing the mask layout to minimize interconnect distances

The worst long-term drift was measured to be approximately 4% per hour.

The timing of a 1-hour chemicalreaction should be accurate to within 3 minutes.

The use of an oscillating pneumatic circuit to drive the operation of a peristaltic pump

Next page

CONCLUSION1.The tuning of oscillator frequency through

the variation of resistor sizes in the circuit, achieving a range of 1 Hz to 100 Hz.

2.No characterized oscillator stability,but establishing in devices that the short-term fluctuation and longterm drift is suitable for lab-on-a-chip applications.

3.The only external input required is a vacuum source, it may be possible to use such devices in limited-resource settings.