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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
2
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
3
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
4
Implant Systems for BioMedical Applications
Totally Implant Cochlear Hearing System
Implant Systems for BioMedical Applications
Visual Prosthesis - Artificial Retina
5
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
6
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
7
Neural Recording
Microelectrodes
Reference :
http://www.acreo.se/acreo-rd/IMAGES/PUBLICATIONS/PROCEEDINGS/ABSTRACT-
KINDLUNDH.PDF
Micro/Nano Needles
Drug Delivery Probes
8
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
9
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.
10
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.
11
Micro/Nano applied to BME
22
Parylene Flexible Prosthetic
Devices
Yu-Chong Tai
Damien Rodger, Wen Li
Caltech Micromachining Lab
Caltech
Caltech Micromachining Group
12
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
13
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)
14
• 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
15
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)
16
USP Classification: Parylene’s Class VI
Parylene as Biocompatible Coating/Sealing Material.
PacemakerMetal
Current Parylene Applications
Electronics coatingNeuroprobe coating
17
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
18
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