Application of Micro fabricated valves based on the principles of thermo pneumatic actuation

M. S. Ramaiah School of Advanced Studies 1

M. Sc. (Engg.) in Electronics System Design

Engineering

GREESHMA SCWB0913004 , FT-2013

4th Module Presentation

Module code : ESE2513

Module name : Low Voltage Electronics

Module leader : Ms. Nireeksha/ Ms. Malathi

Presentation on : 14/02/2014


Application of Micro fabricated

valves based on the principles of

thermo pneumatic actuation

Presentation on


• ABSTRACT

• INTRODUCTION

• THERMOPNEUMATIC MICROVALVE TECHNOLOGY

• REFRIGERATION APPLICATION

• SEMICONDUCTOR PROCESS APPLICATION

• MASS FLOW MEASUREMENT PRINCIPLE

• ADVANTAGES

• DISADVANTAGES

• CONCLUSION

• REFERENCES

Overview


Abstract

In terms of control and distribution of liquids and gases (microfluidics), MEMS-

based devices offers opportunities to achieve increased performance and higher

levels of functional integration , at lower cost, with decreased size and increased

reliability

Microfluidic actuators include distribution microchannels and orifices, microvalves,

micropumps, and microcompressors

Related microsensors are required to measure temperature, flow, pressure,

viscosity, and density

A brief comparison to other actuation techniques is made, science and technology of

silicon-based thermopneumatic microvalves

Expansion valves for refrigeration control


Introduction

Actuators such as pumps, compressors, and valves are used to alter the state of the

fluid pressure, temperature, or flow

Microfabrication techniques created for the semiconductor integrated circuit

industry have found new applications in MEMS research, development and

manufacture

Microvalves are a primary component of microfluidic systems

Actuators rely on a variety of activation mechanism, such as electromagnetic,

electrostatic, pneumatic, bimetallic alloys, shape-memory alloys(SMA), electro-

chemical and thermopnematic

Distribution channels, such as orifices and microchannels, carry the fluid from one

portion of the system to another


Thermopneumatic Microvalve Technology

Figure 1 Cross section of a Thermo

pneumatically Actuated Microvalve

Figure 2 Drill holes in Pyrex

Wafer ultrasonically

Figure 3 Metalize Pyrex wafer

Figure 4 Define membrane

Lithographically (gold oxides,

Photo-resist masks)

Figure 5 Etch membrane

wafer in KOH; strip

masking materials

Figure 6 Define orifice wafer

lithographically

Figure 7 Etch orifice wafer in

KOH

Figure 8 Fabrication sequence for a

normally open, thermopneumatic

valves


Thermopneumatic Microvalve Technology

Figure 9 Estimated flow based on loss coefficient

flow measurements

Figure 10 Relationship between the equilibrium

membrane to inlet

Figure 11 Predicted effect of scaling on microvalve response

time


Refrigeration Application

Normally-open microvalves have been applied to the problem of controlling liquid

flow

Refrigerant liquids present unusual challenges for thermally activated microvalves

The pressure versus flow versus valve power input for one such microvalve is

shown

Figure 12 Pressure vs. R-13a flow vs. pressure

for a representative microvalve


Semiconductor process Applications

The present and future requirements of the semiconductor industry for gas

distribution and control

The thermopnematic actuation principle is employed

Figure 13 Cross section of thermo pneumatically

actuated , normally closed, low leakage shut off

valve

The silicon-ceramic interface is a eutectic bond

The overall dimension are 8mm X 6mm X 2mm, and are roughly scale


Mass flow Measurement principle

Figure 14 Schematic of O-ring used in the vacuum ring

rate shutoff valve

Figure 15 Helium leak rate for vacuum leak-rate for

Microvalves

Figure 16 Schematic representation of the low-

flow MFC

Figure 17 Pressure Sensor Resolution Required to

achieve a given flow resolution, as a Function of critical

orifice Hydraulic Diameter



Figure 18 Schematic representation of the

compressible flow model for the series combination of

normally-open proportional valve, and a critical

orifice.

Figure 19 Measured Flow Characteristics for a Low-Flow

MFC

Figure 20 Measured flow from a 10 sccm Mass-

flow controller

Figure 21 Measurement precision results from a 10 sccm

mass-flow controller



Figure 22 Measurement reproducibility results from

a 10 sccm Mass-Flow controller

Figure 23 Flow model for the MFC

Figure 24 Example Isometric View of a Pressure

regulator, MFC, or shut-off valve.

Figure 25 Isometric View of a 4-Channel Gas stick



Figure 26 Schematic of One Channel of an

Integrated Gas Stick

Figure 27 Size Comparison of Resent and Future Integrated Gas

Sticks/panels


Advantages

Increased performance

Higher levels of functional integration

Higher Resolution

Decreased size

Increased reliability

Disadvantages

The power required for actuation

Response speed

The effect of shrinking size

Structural parameters

Choice of thermopneumatic liquid


Conclusion

The science and technology required to design and fabricate flow distribution

and control devices suitable for semiconductor processing industry

Components such as pressure-based flow models, critical orifices, pressure

temperature sensors normally-closed vacuum leak rate shut off valves, have

developed

These components are combined at higher level into integrated gas panels

which has benefit of smaller size, lower cost, higher resolution , materials

compatibility and lower defect generation which are among the attributes of the

successful application of MEMS-based technology


References

Elisabeth verpoorte and nicof.de.rooij,fellow, (2003). Microfluidics Meets MEMS.

6th ed. Switzerland: University of Neuchâtel. 930-953

Albert K. Henning (1998). Microfluidic MEMS. CA: -. 471-486


Documents

Application of Micro fabricated valves based on the principles of thermo pneumatic actuation