MEMS for Biomedical Applications

Wen Li, Microtechnology Laboratory

Outline

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Introduction to BioMEMS

Enabling Technologies

Applications of BioMEMS

Brain Machine Interface

Intraocular BioMEMS for Glaucoma Management

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What are MEMS?

Microelectromechanical Systems

Micro: sizes ranging from nm to mm

Electro: signal/ control (sense,

compute, etc.)

Mechanical: structure/functioning

(actuate, etc.)

System: integration, communicate,

control

Enabling technology

Existing IC fabrication tools

Batch processing for low cost,

uniform production

Image Ref: Cheng-Hsien Liu(NTHU)

MEMS new possibilities

MEMS & Microsystems

Medicine Neural implants Drug delivery

Bioimaging …

Life science Experimental tools

Lab analysis(cell, DNA, etc.) Animal study

…

Common MEMS Fabrication

Techniques

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Constraints of BioMEMS

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Material requirements

Biocompatibility

Mechanical compatibility

Chemical resistance

Polymer MEMS Advantage

Biocompatible and biodegradable

Better mechanical shock tolerance

Low cost

Disadvantage Mechanical properties change dramatically over a narrow temperature

range (low glass transition temperature and melting point)

Gas/moisture permeable, will need hermetic packaging

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Typical Polymer MEMS

Techniques

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BioMEMS Applications

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Brain Machine Interface (BMI)

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BMI forms a direct communication pathway between the brain and an external device

Neural communication through

Electrical signal

Chemical signal

http://brain-lightning.brainfunctionz.com/brain-machine-interface/

Electrical/Chemical BMI

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Artificial BMI

Electrical

stimulation/recording

Chemical

stimulation/recording

Combined approach

Several types

Surface type

Electroencephalography

(EEG)

Electrocortigography (ECoG)

Penetration type

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Example of Electrical BMI-I

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Penetrating probes (silicon or polymer) for deep brain Stimulation

Diseases: Parkinson’s diseases, epilepsy, etc.

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Michigan Probe

Utah Probe Polymer Probe

https://www.youtube.com/watch?v=WYDoHmg9ECI

Example of Electrical BMI-II

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Artificial Retinal Implant

Diseases: age related macular

degeneration (AMD) and

retinitis pigmentosa (RP), etc

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USC Team

http://www.cnn.com/2009/HEALTH/12/11/bionic.eye/

Example of Chemical BMI

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Wise et al. Proceedings of the IEEE, 2004. 92(1): p. 76-97.

He, B., Neural Engineering.

Bioelectrical engineering. 2005, New

York: Kluwer Academic/Plenum.

John et al.. J. Micromech. Microeng.

21 (2011).

Optogenetics

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Challenges of electrical/chemical BMI: poor spatial resolution,

electrical artifacts, non-selectivity, reliability and stability

Optical stimulation: stimulation or inhibition of specific type of

neurons, temporal precision (millisecond-timescale), long-term

reliability

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http://nmbl.stanford.edu/research/experiments/optogenetics.htm http://www.psmag.com/science/a-light-bulb-moment-in-the-brain-36021/

Micro-Opto-Electro Interface

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We are developing

Flexible, transparent, ECoG

array for electrical recording

Flexible, in-plane integrated

µ-LEDs and ECoG array for

dual-mode neural interface

(optical stimulation and

electrical recording)

Three-dimensional µ-LEDs

array for optical stimulation

of neurons.

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BioMEMS for Glaucoma

Management

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Glaucoma

The second leading cause of blindness (WHO)

~ 67 million worldwide

Over 4 million Americans have glaucoma but only half of those know they have it

~10% of people with glaucoma become blind

Types of Glaucoma

Open-angle glaucoma

Close-angle glaucoma

Normal-tension glaucoma

Congenital glaucoma

Other types

Clinical Interventions

Applanation tonometry

Shape and color of the optic nerve

The complete field of vision

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http://www.glaucoma.org/glaucoma/facts-statistics/glaucoma-facts-and-stats.php

Open-angle glaucoma

Microsystem Approaches

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MEMS IOP sensors

Continuous IOP monitoring

Correlation between IOP fluctuations and glaucoma

Types of MEMS IOP sensors

Wired sensors

Wireless sensors

Passive devices Simple and low-cost

Limited detection range

Low coupling efficiency

Active devices Long detection range

Complex system

Power issue

Other techniques: optical devices, etc.

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K. Katuri et al., IEEE Sensors, vol. 8, no. 1, 2008

Parylene-based IOP Sensor

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Passive wireless IOP sensor RLC resonant circuit

Variable capacitor, inductor, or both

Detection of pressure variance through inductive coupling

No need for battery

Glaucoma Therapy

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Medication

Difficulty in dosage control

Side effects

Surgical treatment

Possible eye infection and inflammation

Temporary treatment

Wound/opening will heal over time

Implantable glaucoma drainage devices (GDDs)

Continuous regulation

Suitable for lifelong glaucoma management

Large size

Excessive fluid drainage

Clogging of the outflow tube

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National Eye Institute http://www.nei.nih.gov/

http://www.google.com/images

Microfluidic Drainage & Drug

Delivery Systems

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MEMS-based valves

Subconjunctival refillable reservoir

Microfluidic flow regulation and valves

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P. Li et al., JMEMS, vol. 19, no. 1, 2010

PJ Chen et al., JMEMS, vol. 16, no. 2, 2007

Reference on MEMS

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Educational Organizations Accreditation Board for Engineering and Technology (ABET)

The Biomedical Engineering Society (BMES)

Journals Lab on a Chip

Journal of Microelectromechanical Systems

Journal of Micromechanics and Microengineering

Sensors and Actuators A, B

Biomedical Microdevices

Analytical Chemistry

Conferences Micro Total Analysis Systems (µTAS)

IEEE MEMS/NEMS

Transducers

Solid‐state Sensors, Actuators and Microsystems Workshop (Hilton Head)

Useful Online Magazines http://www.electroiq.com/index/nanotech‐mems.html

http://www.lab‐on‐a‐chip.com

http://www.mstnews.de

http://www.yole.fr/pagesAn/Micronews/newslett.asp

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