1. 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

2. 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

3. 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

4. Diaphragm
Silicon
Dioxide Layer
Handle Layer
Etched out
Void Cavity
MEMS
Acoustic
Sensor
Project Hypothesis
Unidirectional
Microphone
Packaging

5. Trials – Setup
‘Saksham’, Robotics Development Centre testing ground
7 microphones each 2 meters apart
‘Daksh’ – Master Control Station

6. Microphones positioning (Contd.)
Test 2
Test 1
2 m
2 m
5 m 30 m
9596

7. Microphones positioning (Contd.)
Test 3
Test 4
2 m
5 m 30 m
12 m
2 m
5 m 30 m
12 m
5 m
94
95
96
92
94
95
96
92

8. Trials – Results

9. Numerical Analysis
 Software support: SOLIDWORKS 2011, ProENGINEER Wildfire 4.0,
ANSYS WORKBENCH 14.0

10. A Few Mode Shapes (MS)
MS 1 MS 2 MS 3 MS 4
MS 50MS 25MS 10MS 5

11. Analytical Understanding
Mechanical Vibrations
– S. S. Rao

12. Characteristic Eqn.
(ω2,xo) Eigen Pair

13. 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

14. At Fabrication Lab ‘Sookshma’
Work Bench
Mask
Aligner
Cleanroom
SEM
Spin Coater
Lithography

15. Filter Mask – Positive Photo Film
Filter Design on AutoCAD A3 Positive Photo Film Sheet Printed

16. Jig – Model to Product
Spoutless Tall
Form Beaker
Teflon
Ebonite

17. 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>

18. Etching in Process
Etched out Wafer

19. Diaphragm Development

20. Rough Surface Profile Analysis

21. Smooth Surface Profile Analysis

22. Packaging – Pro-E Model
Circular Base
Conical Cover

23. Packaging – 3D Printed Plastic Model
 Fast
 Simplified
 Compromising
Accuracy

24. Testing – Setup
Pre-Amplifier
Circuit
Packaging

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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 systems
and equipment
 Known for:
Projects in Avionics, Light Combat Aircraft, Unmanned
Aerial Vehicles, Radar Warning Receivers, Tanks, Bridges,
and so on…