MEMS for Biomedical Applications
Wen Li, Microtechnology Laboratory Outline
Introduction to BioMEMS
Enabling Technologies
Applications of BioMEMS Brain Machine Interface Intraocular BioMEMS for Glaucoma Management
Microtechnology Laboratory 11/7/2012
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 Life science Neural implants Experimental tools Drug delivery Lab analysis(cell, DNA, etc.) Bioimaging Animal study … …
Common MEMS Fabrication Techniques
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Constraints of BioMEMS
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)
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/
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Electrical/Chemical BMI
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
Penetrating probes (silicon or polymer) for deep brain Stimulation Diseases: Parkinson’s diseases, epilepsy, etc.
Michigan Probe
Utah Probe Polymer Probe
https://www.youtube.com/watch?v=WYDoHmg9ECI Microtechnology Laboratory 11/7/2012
Example of Electrical BMI-II
Artificial Retinal Implant
Diseases: age related macular degeneration (AMD) and retinitis pigmentosa (RP), etc
USC Team http://www.cnn.com/2009/HEALTH/12/11/bionic.eye/
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Example of Chemical BMI
John et al.. J. Micromech. Microeng. 21 (2011).
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.
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Optogenetics
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
http://www.psmag.com/science/a-light-bulb-moment-in-the-brain-36021/ http://nmbl.stanford.edu/research/experiments/optogenetics.htm
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Micro-Opto-Electro Interface
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.
Microtechnology Laboratory 11/7/2012
BioMEMS for Glaucoma Management
Open-angle glaucoma 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
Microtechnology Laboratory http://www.glaucoma.org/glaucoma/facts-statistics/glaucoma-facts-and-stats.php 11/7/2012
Microsystem Approaches
MEMS IOP sensors Continuous IOP monitoring Correlation between IOP fluctuations and glaucoma
Types of MEMS IOP sensors Wired sensors K. Katuri et al., IEEE Sensors, vol. 8, no. 1, 2008 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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Parylene-based IOP Sensor
Passive wireless IOP sensor RLC resonant circuit Variable capacitor, inductor, or both Detection of pressure variance through inductive coupling No need for battery
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Glaucoma Therapy
Medication Difficulty in dosage control Side effects
Surgical treatment Possible eye infection and inflammation Temporary treatment Wound/opening will heal over time
National Eye Institute http://www.nei.nih.gov/ Implantable glaucoma drainage devices (GDDs) Continuous regulation Suitable for lifelong glaucoma management Large size Excessive fluid drainage Clogging of the outflow tube
http://www.google.com/images
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Microfluidic Drainage & Drug Delivery Systems
MEMS-based valves Subconjunctival refillable reservoir Microfluidic flow regulation and valves
PJ Chen et al., JMEMS, vol. 16, no. 2, 2007
P. Li et al., JMEMS, vol. 19, no. 1, 2010
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Reference on MEMS
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
Microtechnology Laboratory 11/7/2012
Microtechnology Laboratory 11/7/2012