imrse-2021.pptx

DESIGN AND ANALYSIS OF A SENSITIVE
MICRO-SCALE CAPACITIVE ACCELEROMETER
FOR IMPLANTABLE HEARING AID WITH
AUTONOMOUS ENERGY HARVESTER SYSTEM
Presented By:-
Dr. Prateek Asthana
Assistant Professor
Bharat Institute of Engineering and
Technology, Hyderabad
Authors:
Dr. Prateek Asthana
Dr. Apoorva Dwivedi
Dr. Gargi Khanna

CONTENTS
05-10-2023
DESIGN AND ANALYSIS OF A SENSITIVE MICRO-SCALE CAPACITIVE ACCELEROMETER FOR
IMPLANTABLE HEARING AID WITH AUTONOMOUS ENERGY HARVESTER SYSTEM
2
 Introduction
 Fully Implantable Hearing Aid
 Device Structure
 Simulation Results
 Seesaw Shaped Piezoelectric Energy Harvester
 Device Structure
 Simulation Results
 Conclusion
 References

INTRODUCTION
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• According to the World Health Organization, 15% of adults, or 766 million
individuals worldwide, have substantial hearing loss.
• In most situations of hearing loss, conventional hearing aids can provide
adequate restoration.
• Wearing external hearing aids, on the other hand, carries a social stigma.
• The social stigma associated with wearing external hearing aids, on the
other hand, prevents many patients from even considering them.
• As a result, semi-implantable middle ear and cochlear prosthetic systems
are becoming more popular.
• The MEMS capacitive accelerometer is intended to be mounted on the
umbo and used as a middle ear microphone.

CONTENTS
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Fig. 1 Proposed fully implantable microphone in middle ear

FULLY IMPLANTABLE HEARING AID
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• The comb drive capacitive accelerometer used in this work comprises four
folded beams as suspension system and a proof mass with movable
fingers as shown in Fig. 2.
• The fixed parts contain two anchors and left/right fixed fingers. The four
folded beams connect the movable central proof mass to both the
anchors.
• The capacitive accelerometer is fixed onto the umbo.
• The eardrum vibrates in reaction to incoming sound, causing the umbo to
vibrate as well. The sensor is acted upon by the incoming pressure.
• The proof mass with the moveable fingers moves in the direction of body
force under the influence of this force, changing the capacitance between
the movable and fixed finger.

DEVICE STRUCTURE
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Geometry Parameter Value (µm)
Length of sense finger 90
Gap spacing (x1, x2) 1, 2
Width of spring beam 2
Width of sense finger 1
Length of proof mass 740
Thickness of the device 12.5
Width of proof mass 884
Length of spring beam 72
Fig. 2 The accelerometer prototype design in
COMSOL MULTIPHYSICS

SIMULATION RESULTS
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Fig. 3 First resonant frequency of the optimized device Fig. 4 Maximum stress induced in the model

SIMULATION RESULTS
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Fig. 5 Maximum displacement of the model at 1 g acceleration
Parameters Simulatio
n Results
Displacement Sensitivity
(nm/g)
2.50
Nominal Capacitance (pF) 4.72
Capacitive Sensitivity (fF/g) 5.80

SEESAW SHAPED PIEZOELECTRIC
ENERGY HARVESTER
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• The emphasis is on micro/nanoscale energy harvesting from the environment. Because
energy from the environment, captured in the form of vibrations, is generally modest, as is
the power need for micro-scale devices, ambient vibrations are a prominent source of
energy harvesting due to their pervasive presence everywhere.
• Two piezoelectric layers have been deposited one at top and the other at the bottom of the
cantilever structure, forming a piezoelectric bimorph cantilever. PZT based materials and
devices are not being preferred in practical applications.
• A lead-free material having better or equivalent properties to PZT would be preferred as an
alternative.
• We have used Zinc Oxide (ZnO) as lead free piezoelectric material. The structure uses
silicon as the substrate material for the cantilever beam and for the proof mass on the
device.

DEVICE STRUCTURE
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Fig. 6 The seesaw shaped energy harvester prototype design in
COMSOL MULTIPHYSICS

SIMULATION RESULTS
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Fig. 7 Maximum stress induced on the top
piezoelectric layer
Fig. 8 Maximum stress induced on the bottom
piezoelectric layer.

SIMULATION RESULTS
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Fig. 9 Maximum electric potential developed on the
piezoelectric energy harvester.

CONCLUSION
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• The accelerometer inhabits a small sensing area of 1mm2, overall packaged weight less
than 20mg and the resonant frequency of nearly 10,000Hz.
• The accelerometer can be surgically implanted and works well within the normal speech
conversational range.
• The capacitance of 4.72pF, displacement sensitivity of 2.50nm/g and capacitive
sensitivity of 5.80fF/g is obtained.
• Along with the hearing aid, a energy harvester working on vibration of the ear bone is
designed to power the accelerometer with a voltage of 1.2 V.
• The full system is capable of having autonomous power throughout the device lifetime.
• Hence, the proposed design can be recommended as a microphone for the fully
implantable hearing application.

REFERENCES
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1. Wang, D. (2017) ‘Deep learning reinvents the hearing aid’, IEEE Spectrum, Vol. 54 No. 3, pp.32-37.
2. Varshney, S. (2016) ‘Deafness in India’, Indian Journal of Otology, Vol. 22 No. 2, p.73.
3. Dwivedi, A., & Khanna, G. (2018). Sensitivity Enhancement of a Folded Beam MEMS Capacitive Accelerometer-Based Microphone for
Fully Implantable Hearing Application. Biomedizinische Technik. Biomedical engineering, 63(6), 699-708.
4. Dwivedi, A., & Khanna, G. (2020). A microelectromechanical system (MEMS) capacitive accelerometer-based microphone with
enhanced sensitivity for fully implantable hearing aid: a novel analytical approach. Biomedizinische Technik. Biomedical Engineering.
5. Dwivedi, A., Asthana, P., & Khanna, G. (2020). Effect of Micro Lever Width on the Mechanical Sensitivity of a MEMS Capacitive
Accelerometer. In Advances in VLSI, Communication, and Signal Processing (pp. 525-532). Springer, Singapore.
6. Asthana, P., & Khanna, G. (2019). A broadband piezoelectric energy harvester for IoT based applications. Microelectronics Journal,
93, 104635.
7. Khanna, G., & Asthana, P. (2016, March). A comparative study of circuit for piezo-electric energy harvesting. In 2016 3rd International
Conference on Computing for Sustainable Global Development (INDIACom) (pp. 1689-1694). IEEE.
8. Asthana, P., & Khanna, G. (2020). Modeling and optimization of a wide-band piezoelectric energy harvester for smart building
structures. International Journal of Modeling, Simulation, and Scientific Computing, 11(02), 2050009.
9. Asthana, P., & Khanna, G. (2020, May). A wideband zinc oxide energy harvester for IoT based sensor. In 2020 Zooming Innovation in
Consumer Technologies Conference (ZINC) (pp. 251-252). IEEE.
10. Asthana, P., & Khanna, G. (2020). Power amplification interface circuit for broadband piezoelectric energy harvester. Microelectronics
Journal, 98, 104734.

05-10-2023
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