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In Vivo Micro Medical Devices

Yu-Chong Tai, PhD

Prof. of EE, ME and BE

Caltech

NSF Short Course, July 16-18, UCLA

Reader’s Digest1000th Issue, Aug., 2005

14AMAZINGTRENDS

That Will ChangeYour Life

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Micro/Nano applied to BME

Taken from : http://mems.colorado.edu/c1.res.ppt/ppt/g.tutorial/ppt.htm

Angiojet

Taken from : www.heartcenteronline.com

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Micro/Nano applied to BMEB

all

oo

n A

ng

iop

last

y

an

d

Ste

nt

Pro

ced

ure

Stent Procedure

http://www.mdmercy.com/vascular/discoveri

es/balloon_stent_gif_big.html

http://www.med.umich.edu/1libr/aha/aha_dil

ation_art.htm

Balloon Angioplasty

Implant Systems for BioMedical Applications

Cochlear Hearing System

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Implant Systems for BioMedical Applications

Totally Implant Cochlear Hearing System

Implant Systems for BioMedical Applications

Visual Prosthesis - Artificial Retina

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Intraocular Stimulation

ElectrodesReference : Lutz Hesse, Thomas Schanze, Marcus Wilms and Marcus Eger, “Implantation of retina stimulation

electrodes and recording of electrical stimulation responses in the visual cortex of the cat”, Graefe’s Arch Clin Exp

Ophthalmol (2000) 238:840–845

Micro/Nano applied to BME

An implantable blood

pressure sensor developed

by CardioMEMS

Surgical microgripper actuated by SMATaken from

http://www.ee.ucla.edu/~jjudy/publications/conference/msc_2000_judy.pdf

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Implant Systems for BioMedical Applications

Electrode Arrays for Neural Control

Micro/Nano applied to BME

Micromachined silicon neural probe arrays

Taken fromhttp://www.ee.ucla.edu/~jjudy/publications/conference/msc_2000_judy.pdf

Michigan Probe

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Neural Recording

Microelectrodes

Reference :

http://www.acreo.se/acreo-rd/IMAGES/PUBLICATIONS/PROCEEDINGS/ABSTRACT-

KINDLUNDH.PDF

Micro/Nano Needles

Drug Delivery Probes

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Multi-electrode Neural

Recording

Reference :

http://www.nottingham.ac.uk/neuronal-networks/mmep.htm

Reference :

http://www.cyberkineticsinc.com/technology.htm

Implant Systems for BioMedical Applications

Upper Extremity Control System

1968

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Feedback Control through Central Nerve System—A Concept

1960’s

Implant Systems for BioMedical Applications

Some Historical Records

• 1959, Mackay, R.S.,” Radio Telemetry from within the

Human Body”, Trans. IRE, ME-6, pp.100-105.

• 1967, Ko, W. H and Neuman MR, “Implant Biotelemetry and

Microelectronics” Science. Apr; 156(773):351-60.

• 1977, Hambrecht, F. T., Reswick, J. B. (eds.): “Functional

Electrical Stimulation: Applications in Neural Prostheses”,

Marcel Dekker, New York.

• 1980, Amlaner, C. G. and MacDonald, D. M, (Ed.) “A

Handbook on Biotelemetry and Radio Tracking”, Pergamon

Press, Oxford and New York.

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Implant Systems for BioMedical Applications

Nuclear Battery –β Cell

Implant Systems for BioMedical Applications

• Implant Micro/Nano Systems Can Contribute

Significantly in Life Science Research, Medical

Treatment, and Patient Care.

• Implant Micro/Nano Systems Present Great

Promises and Challenges to Engineering and Bio-

Medical Research Communities.

• Implant Micro/Nano Systems Require Team Effort

of Life Scientists, Engineers and Medical

Professionals to Provide Functional Systems to

Treat Patients, as well as to Maintain Health.

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Micro/Nano applied to BME

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Parylene Flexible Prosthetic

Devices

Yu-Chong Tai

Damien Rodger, Wen Li

Caltech Micromachining Lab

Caltech

Caltech Micromachining Group

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Why retinal implants?

• The pathologies Age-

Related Macular

Degeneration (AMD)

and Retinitis

Pigmentosa (RP) are

the leading causes of

age-related blindness

in humans, 2M patients

in US

• These diseases are

characterized by a loss

of photoreceptors at

the outer retina

Possible approaches

• Possible approaches

– Epiretinal

– Subretinal

• Ab interno(trans-retinal)

• Ab externo(trans-scleral)

– Optic nerve

– Cortical / thalamic

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Current prototype and future trend

State-of-the-art Epiretinal Electrodes

• Flexible epiretinal electrodes – 4x4 array.

• Encouraging results, but need larger array.

• Current technology not scalable, need MEMS

electrodes.

(Second Sight, Model 1)

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• Discrete components: capacitors,coils, tec.

• Multi-component system

• Conventional packaging (wirebond, solder, etc)

• Too thick and rigid for implantation

• Not scalable to high-density electrodes

• Too large…

Current State-of-the-art Device

(Stieglitz’s Germany)

State-of-the-art Retinal Implants

Stieglitz (Fraunhofer) Germany, 2004

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Intraocular

RF coil

Packaged

ASIC

High lead-count

flexible cable

Epiretinal

multielectrode

array

Integrated Retinal Implants

• To microfabricate a flexible multielectrode system for an epiretinal stimulator using parylene

• System comprises:– An intraocular radio-frequency (RF) coil to wirelessly receive power and data from an external camera and external RF coil

– An application-specific integrated circuit (ASIC) that recovers this power and data and converts it into analog and digital driving signals for the multielectrode array

– An epiretinal multielectrode array

• Packaging that interconnects and isolates all components from the corrosive, saline environment of the vitreous humor

Flexible parylene IRP paradigm

• Parylene C is USP Class VI biocompatible

• Parylene is microfabrication/post-IC compatible

• Parylene deposition occurs in a room-temperature chamber as a highly conformal, pinhole-freecoating

• Parylene is transparent and has ideal mechanical strength and flexibility characteristics (Young’s modulus: 4 GPa ~ Nylon), facilitating surgical implantation and out-patient monitoring of device stability

• Parylene is an ideal electrical insulator

• Metal can be sandwiched between two layers of parylene, sealing the interconnect metal from the corrosive environment, and preventing tissue response

• Metal can be selectively exposed (e.g. where stimulation of the retina is desired)

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USP Classification: Parylene’s Class VI

Parylene as Biocompatible Coating/Sealing Material.

PacemakerMetal

Current Parylene Applications

Electronics coatingNeuroprobe coating

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6 month parylene C implantation

• Parylene C implanted in the vitreous cavity of

the right eyes two rabbits for six months

• No immune response

Flexible Parylene Cable Electrodes

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Parylene-Metal-Parylene

Adhesion Study

-28 days>100 daysYes~4.67umParylene-Cr-Parylene

->32 days>32 daysYes~9.2umParylene-Ti-Parylene

->32 days>32 daysYes~9.2umParylene-Au-Parylene

~9.2um

~4.67um

~4.67um

Thickness

of each

parylene

layer

->32 days >32 days YesParylene-Cr-Parylene

-70 days>100 daysYesParylene-Au-Parylene

~20 years23 days80 daysYesParylene-Ti-Parylene

90 deg. C