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 Microtechnology Laboratory 11/7/2012 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 Microtechnology Laboratory 11/7/2012 Typical Polymer MEMS Techniques Microtechnology Laboratory 11/7/2012 BioMEMS Applications Microtechnology Laboratory 11/7/2012 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/ Microtechnology Laboratory 11/7/2012 Electrical/Chemical BMI Artificial BMI Electrical stimulation/recording Chemical stimulation/recording Combined approach Several types Surface type Electroencephalography (EEG) Electrocortigography (ECoG) Penetration type Microtechnology Laboratory 11/7/2012 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/ Microtechnology Laboratory 11/7/2012 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. Microtechnology Laboratory 11/7/2012 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 Microtechnology Laboratory 11/7/2012 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. Microtechnology Laboratory 11/7/2012 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 Microtechnology Laboratory 11/7/2012 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 Microtechnology Laboratory 11/7/2012 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 Microtechnology Laboratory 11/7/2012 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 .