a recent developement in Ultrasonic transducers,making the transducers based on capacitive transducers principle instead of piezoelectric effect

1. Sree Vidyanikethan Engineering
College
Rotational Capacitive
Micromachined
Ultrasonic Transducers
Guided by
Mrs.A.Yasmine Begum
By
D.Sai lohith
11121A1017

2. Contents
Transducers- Acostic transducers
What are MEMS?
Difference between normal UT and CMUT
CMUT- Structure, principle, fabrication
Comparison of piezo-electric and CMUT
Rotational CMUT- Fabrication,experiment and it’s
results
Applications
conclusion
References

3.  Acoustic Transducers
 Ultrasonic transducers

5. What is the difference between normal
ultrasonic transducer and CMUT?

6. • Piezoelectric property
• Capacitive transducer
Where ,C is the capacitance, ε0 is the permittivity of free space constant, K is
the dielectric constant of the material in the gap, A is the area of the plates,
and d is the distance between the plates.
where S is the area of capacitor plates, V is the applied
bias voltage, is the permittivity of free space between capacitor
plates, and d is the distance between the capacitor plates.

7. CMUT structure

9. Operation priciple

11. Fabrication
• Sacrificial release process
• Wafer bonding,etc

12. Step 1: Starting waferStep 2: Deposition of sacrificial layerStep 3: Deposition of structural layerStep 4: Pattern the top polysilicon layerStep 5: Deposit a second sacrificial layerStep 6: Pattern and Etch the sacrificial layersStep 7: Deposit polysilicon structural layer.Step 8: Pattern Polysilicon.Step 9: Sacrificial layer removal and freeing of
structures

13. Why we are going to CMUT over
Piezoelectric Ultrasonic transducer?

14.  batch-production
 wide bandwidth
 easier to fabricate
 integration with supporting electronic
circuits
 Wider temperature range

15. Why we are going to Rotational CMUT
instead of normal CMUT?

16. • no internal damping
• negligible thermal mechanical noise
• enables lower resonant frequencies
• higher compliance to acoustic signals
• frequency response up to 200 kHz

17. Rotational Capacitive Micromachined Ultrasonic
Transducers

18.  Sacrificial release Process

22. SEMs

26. Applications
2D and 3D arrays
Intravascular ultrasound (IVUS)
Second-harmonic imaging
Hydrophones
Photo-Acostic imaging

27. Conclusion
 Rigorous modeling and acoustic
characterization of the rotational
cMUT
 as does a detailed comparison of the
device technology against other
airborne ultrasonic transducers
 1 μm deflection, implying that at least
10× higher compliance diaphragms
are realizable by use of the beam-
coupled design.

28. References

29. Some referable websites about cMUTs
• http://www.kyg.stanford.edu/khuriyakub/opencms/en/research/c
muts/Principles/
• http://www.microfab.de/mems/ultrasonictransducers/cmut.html
• http://www-
kyg.stanford.edu/khuriyakub/opencms/en/research/cmuts/general
/index.html
• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3158704/
• http://www-old.me.gatech.edu/mist/cmut.htm

30. Thank you