Design of a

Novel MEMS Based Acoustic Filter

for Gunshot Detection

PROJECT GUIDE: Dr. Gautam S. Chandekar

GROUP MEMBERS: Neha Sharma B80200865

Tejaswita Patil B80200864

Ishita Mukherjee B80200825

Pooja Shivale Patil B80200826

Outline

1. Work Statement

2. Project Hypothesis

3. Gun Shot Trials

4. Numerical Analysis

5. Analytical Understanding

6. Fabrication

7. Packaging

8. Testing

9. Conclusion and Future Scope

10. Time Frame, Budget and Company Profile

Work Statement

Problem statement:

To Design and Develop a Novel MEMS based Sensor to

detect Acoustic Signature of Gun Shot

Why:

• Traditionally available and currently under research v/s

MEMS based concept sensor

• Defense v/s Civil Applications

Where:

‘Sookshma’, Microsystems Labs,

R&DE (Engrs.), Dighi, Pune

Diaphragm

Silicon

Dioxide Layer

Handle Layer

Etched out

Void Cavity

MEMS

Acoustic

Sensor

Project Hypothesis

Unidirectional

Microphone

Packaging

Trials – Setup

‘Saksham’, Robotics Development Centre testing ground

7 microphones each 2 meters apart

‘Daksh’ – Master Control Station

Microphones positioning (Contd.)

Test 2

Test 1

2 m

2 m

5 m 30 m

9596

Microphones positioning (Contd.)

Test 3

Test 4

2 m

5 m 30 m

12 m

2 m

5 m 30 m12 m

5 m

94

9596

92

94

9596

92

Trials – Results

Numerical Analysis

Software support: SOLIDWORKS 2011, ProENGINEER Wildfire 4.0,

ANSYS WORKBENCH 14.0

A Few Mode Shapes (MS)

MS 1 MS 2 MS 3 MS 4

MS 50MS 25MS 10MS 5

Analytical Understanding

Mechanical Vibrations – S. S. Rao

Characteristic Eqn.

(ω2,xo) Eigen Pair

At Fabrication Lab ‘Sookshma’

• Processes (chemicals)

• Cleaning

• Wet etching (TMAH)

• Sputtering (Ar gas

atm.)

• UV LIGA

• Spin Coating (SU8)

• Equipments (chemicals)

• SEM-Scanning

Electron Microscope

• Oxidation Furnace

• Chemical Workbench

• Reflux Water bath (as

manufactured)

Class 1000 and Class 10,000 cleanroom facilities

At Fabrication Lab ‘Sookshma’

Work Bench

Mask

Aligner

Cleanroom

SEM

Spin Coater

Lithography

Filter Mask – Positive Photo Film

Filter Design on AutoCAD A3 Positive Photo Film Sheet Printed

Jig – Model to Product

Spoutless Tall

Form Beaker

Teflon

Ebonite

Fabrication Initiation

[MEMS Mechanical Sensors, Stephen Beeby]

Thermally grown oxide layer on 2” Si wafer

Spin coat +ve photoresist using a set recipe

(both sides)

UV Lithography to pattern the mask on

properly aligned wafer

Etch SiO2 with bHF Etchant (SAFETY IMP!)

Strip photoresist by acetone

Major Flat <110>

Wafer Surface

<100>

Etching in Process

Etched out Wafer

Diaphragm Development

Rough Surface Profile Analysis

Smooth Surface Profile Analysis

Packaging – Pro-E Model

Circular Base

Conical Cover

Packaging – 3D Printed Plastic Model

Fast

Simplified

Compromising

Accuracy

Testing – Setup

Pre-Amplifier

Circuit

Packaging

Testing – Characteristics

0

1

2

3

4

5

6

7

8

Amplitude (V)

Output Frequency (Hz)

Output Freq. = Input Freq.

Output Freq. | (With diaphragm = Without Diaphragm)

Low Amplitude generated by Freq. Generator at Low Freq.

Temporary Packaging => Inadequate Sealing

Concluding Remarks

Peak Amplitude FFT Peak Frequency = 380 Hz

SiO2 material wafers

3D printed plastic model

Trial o/p Characteristics Plot range shifted due to

leakage and low amplitude

• Small size

• Fab. – fast, efficient,

less complicated

• Simplified, fast

• Matl. compromised

• Accuracy drop

Future Scope

Hermetically sealed metal package with glass

to metal seals welded to it to best suit military

applications

Vary diaphragm attaching &/or mounting

techniques

Align diaphragms in Arrays or Cubical

orientation for directionality & vector sensing

Time Frame Followed

Work/Month Aug Sept Oct Nov Dec Jan Feb Mar AprMayJune

Software

Design inputs

Design/

Prototyping

Analysis/

Univ. Exam.

Fabrication

Packaging

Report

writing

Final Split-Up Budget

Sr. No. Items Units Cost/Unit (Rs.) Total Cost (Rs.)

1 Si Wafer ( 2”) 10 3000 30,000

2 Microphones (Condenser

type)

10 500 5000

3 Signal Conditioning Module 1 30,000 30,000

4 Chemicals and Echants NA NA 5000

5 Packaging Material NA NA 8000

6 Others (Travelling, etc.) NA NA 2000

Total Cost 80,000

R&DE (Engrs.), Dighi, Pune

Formed: 1958

[Technical Development Establishment +

Directorate Technical Development and Production]merging with Defence Science Organization

Works under:

Defence Research and Development of Ministry of Defence

Undertakes:

Design and Development of world class weapon systemsand equipment

Known for:

Projects in Avionics, Light Combat Aircraft, UnmannedAerial Vehicles, Radar Warning Receivers, Tanks, Bridges,and so on…