SOME RECENT DEVELOPMENTS IN THE - ewh.ieee.orgewh.ieee.org/r10/tainan/embs/talks/taylor_talk.pdf ·...
Transcript of SOME RECENT DEVELOPMENTS IN THE - ewh.ieee.orgewh.ieee.org/r10/tainan/embs/talks/taylor_talk.pdf ·...
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SOME RECENT DEVELOPMENTS IN THEDESIGN OF BIOPOTENTIAL AMPLIFIERS FOR
ENG RECORDING SYSTEMS
John Taylor, Delia Masanotti, Vipin Seetohul and Shiying Hao
Department of Electronic and Electrical EngineeringUniversity of Bath, UK
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ACKNOWLEDGEMENTS
Professor N Donaldson, Department of Medical Physics & BioengineeringUniversity College, London, UK
Dr P Langlois, Department of Electronic and Electrical Engineering,University College, London, UK
Dr J Robbins, Department of Pharmacology, King’College,London, UK
Dr A Sapelkin, Department of Physics, Queen Mary University,London, UK
Dr R Rieger, Department of Electrical Engineering,National Sun Yat-sen University, Taiwan
Dr D Pal, Department of Electronics &Communication Engineering, B.I.T. Mesra, India
Dr M Schuettler, Department of Microsystems Engineering,University of Freiburg, Germany
Dr N Rijkoff Centre for Sensory Motor Interaction (SMI), University ofAalborg, Denmark
Engineering and Physical Sciences Research Council (UK) (EPSRC)
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SUMMARY
The importance of real-time recording of electroneurogram (ENG)signals
The difficulties of achieving a stable interface between tissue andelectronic devices
Illustrations of current problems being studied at Bath University1 Velocity selective recording (VSR) of ENG signals2 In vitro recording of ENG from cloned neurons
Some possible future directions
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THE IMPORTANCE OF ENG RECORDING
Although this area has been researched for some time, there isstill much demand for improved systems for real-time ENGrecording. Interest comes from eg:
•Neuroscientists requiring experimental data in fields such asneurophysiology and neuropharmacology
•Engineers requiring inputs for systems to control FunctionalElectrical Stimulation (FES) systems for a variety ofrehabilitation applications such as neurogenic urinaryincontinence by stimulation of the sacral roots
•There is a demand for recording methods with improvedfunctionality, eg. Velocity/diameter selective recording (VSR)
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NERVE CUFFS FOR ENG RECORDING
electrodes
nerve
cuff
Avery and Wespic(1973)
Avery(1973)
Naples et al Kallesoe (1996)(1988)
Nerve cuff with tripolarelectrode assembly Various types of cuff design
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MULTIELECTRODE CUFF (MEC)
ceramicadapter
cable
cuff
M Schuettler, 2006
•Polyimide thin-film technology
•Sputtered platinum electrodes
•Etched using oxygen plasma.
•The final MEC was 1.5 mm indiameter, 40 mm long andcarried eleven 0.5 mm wide,ring-shaped platinumelectrodes
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RECORDING ENG USING NERVE CUFFS
Nerve
Cuff
Electrode
Amplifier
From tissue
To the central nervoussystem
+
-
This type of cuff/amplifier connectionis called a Quasi Tripole (QT). Itprovides good suppression of EMGand other artifacts. It only requires oneamplifier and is relatively simple toimplement. It has been much used inpractical ENG recording systems.
Output
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10 CHANNEL ENG RECORDING SYSTEM
(N-2)
2nd-rankamplifiers
1st-rankamplifiers
nerve
electrode(rings)
insulatingcuff
adder
bandpassfilter
timedelays
output forone matchedvelocity
etc
(N-1)
(0)
(N-3)
AC couplingstage
subtractors
etc
cuff
Signal processing unit(SPU-digital)
digitisation
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PREAMPLIFIER SCHEMATIC
VSS
VDD
Vref
Vout
Vin+ Vin-
34k
60k
50pFIbias
Q1 Q2
M1 M2
M4M5 M6
Q3
M7
M8M9
M10 M11
M12
M3
11
3mm
ACCoupling
Stage
ChannelSelection MUX
2nd rankAmps
Low-noise Pre-amps
10 CHANNEL ENG RECORDING SYSTEM
Die mounted in PGA packageASIC layout
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EXPERIMENTAL SETUP FOR MEC RECORDINGS
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XENOPUS FROG PREPARED FORREMOVAL OF SCIATIC NERVE
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NERVE FITTED WITH MULTIELECTRODE CUFF INVITRO
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MEASURED RESULTS IN FROG
Stimulation intensity 0.13 µC Stimulation intensity 1.01 µC
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MEASURED VSR DATA IN FROG
Delay profiles corresponding totwo different stimulation intensities:
grey: 1.01 µC, white: 0.13 µC.
The bars have a width of 25 µs(reciprocal value of thesampling frequency)
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BI-DIRECTIONAL INTERFACING OFELECTRONICS AND CULTURED NEURONS
•This is a collaborative programme involving E&EE at Bath, KCL/Guy’sHospital (London), Dept of EE at University College (London) and theDepartment of Physics at Queen Mary University (London)
•The overall aim is to enhance our understanding of how mammaliannerve cells can be connected optimally to integrated electronic circuitryfor neurobiological research and medical applications
•We intend to find an alternative method to traditional patch clampingwhich is non-intrusive, less labour intensive in use and is based on asimple, cheap, reproducible CMOS integrated circuit without any needfor elaborate post-processing
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nucleus
axon
dendrite
cell body
terminal
0.2-20µm5-400µm
+
-
+
+
+
+
+
-
--
- +
-
-
+-
-
+-
++
-
+-
+
+-
+
-
+
+
+
-
-
+
+
culture medium
+ +
+
-
-
-
- cell membrane
sealing gap
cleft
sealing gap
+
NEURON-ELECTRODE INTERFACE: EQUIVALENT CIRCUIT
Si substrate
metallic pad insulating layer
CMOS circuitryextracellular signal
Vout
Cel
Rspr
Rel
Rseal
Csh
Rm
CRL
ENaEk EL
RkRNa
Vout
VM
gK gLgNa
Cel
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PSPICE REALISATION OF THE HODGKIN-HUXLEY MODELOF A NEURON (1952)
VV
0
C71u
+-
G7
G
GAIN = 1
0.07
0
Vmv
-0.010613
VL
1000
POTASSIUM CHANNEL
0
R81e12
.0003
SODIUM CHANNEL
C81000u
R9
1e12
3PWR
25 0.1
EXP
1.000
-1
ILgL
-1PWRS
0.0555
V
EXP
4
Beta(m)
Alpha(m)
+-
G8
G
GAIN = 1
R10
1e12
V3
TD = 20m
TF = 1pPW = 20mPER = 30m
V1 = 0
TR = 1p
V2 = -100
1
V
0
0.036
C91000u
R11
1e12
0
30 0.1
LEAKAGE CHANNEL
EXP
0.05
1.000
gNa
-1PWRSEXP
Alpha(h)
Beta(h)
+-
G9
G
GAIN = 1
gK
V
.001
Vmv
ITotal
Vmv
n
m
Voltage Clamp
Cm
h
IK
.012
Vmv
-0.115
INa
VNa
0.12
C101000u
R12
1e12
4PWR
10 0.01
EXP
1.000
0.1 -1
-1PWRS
0.0125
EXP
0.125
Alpha(n)
Beta(n)
+-
G10
G
GAIN = 1
V
VKV
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PAD-ONLY CHIP LAYOUT
Chip layout Packaged Die
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GROWING NEURONAL CELLS ON CMOS
NG108-15 (neuroblastoma xglioma hybrid) cells, stainedwith methyl blue
Grown on CMOS microchipspre-coated with a cationicpolymer, (PE1), for 5 days
100μm
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NEURONAL GROWTH ON POROUS SILICONEtched from polysilicon on a CMOS chip
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ELECTRICAL IMPEDANCE SPECTROSCOPY (EIS) MEASUREMENTS ONPACKAGED CMOS CHIPS
10-1 100 101 102 103 104 105 106103
104
105
106
107
108
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Frequency (Hz)
|Z|
pin1_chip1_31may06.zpin2_chip1_31may06.zpin3_chip1_31may06.zpin4_chip1_31may06.zpin5_chip1_31may06.z
10-1 100 101 102 103 104 105 106
-100
-75
-50
-25
0
25
Frequency (Hz)
thet
a
Packaged die with insulated bond wiresAveraged EISmeasurements
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FUTURE WORK
•Neural Prostheses: (i) complete the demonstration of velocityselectivity (start January 2007) (ii) consider new methods of neuralrecording, e.g. using optoelectronics
•Electro-neural Interfacing: (i) Demonstrate capture of ENG fromsingle excited neurons; design on-chip signal processing foroptimum SNR. (ii) Complete modelling work
•SMART Orthopaedic Sensors: (i) Develop an optimal implantedsensor for hip micromotion detection and verify with in-vitroexperiments. (ii) Develop other possible applications for the use ofSMART sensors and actuators in modern orthopaedic applications
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SYSTEM SPECIFICATION
15 nA, 20 nA, +,- inputs< 100 nAResidual DC input current
291 nV< 300 nVInput-referred rms voltage noise1 Hz -5 kHz
17 nV/√Hz, 1.5 nV/√Hz20 pA/√Hz, 2 pA/√HzInput-referred current noise density1 Hz, 1 kHz
11.5 nV/√Hz, 3.8 nV/√Hz20 nV/√Hz, 4 nV/√HzInput-referred voltage noise density1 Hz, 1 kHz
82 dB100 dBCMRR @ 1kHz
310 Hz, 3.3 kHz300 Hz, 3.5 kHzBandwidth
10,10010,000Midband gain
12 mm2Circuit area
24 mW< 50 mWPower consumption
±2.5 V±2.5 VPower supply
10Number of channels
MeasuredSpecificationParameter