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Research Paper

Wireless Point-of-Care Diagnosis for Sleep Disorder With Dry Nanowire Electrodes

[+] Author and Article Information
Vijay K. Varadan

 University of Arkansas, Fayetteville, AR 72701

Sechang Oh, Hyeokjun Kwon, Phillip Hankins

Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701

J. Nanotechnol. Eng. Med 1(3), 031012 (Aug 27, 2010) (11 pages) doi:10.1115/1.4002138 History: Received June 25, 2010; Revised June 29, 2010; Published August 27, 2010

Currently, available sleep monitoring systems use electrical recording where the electrodes make contact with the patient’s skin using a conducting gel. The electrode wires are connected to a processing recording system. The subject has to be in close proximity of these machines due to the direct electrical connections with the body and the machine. The conductive gel along with many wires connected to the biopotential electrodes makes them uncomfortable for the subject, with the result that recording and monitoring of the patient’s sleep patterns can become very difficult. The patient has to be in a sleep lab and/or a hospital at all times and at least one technician needs to watch the patient’s sleep behavior via video. The patient may not experience normal sleep patterns under such environments and as such, the diagnostic results are not really very conclusive. The commonly monitored biopotential electrodes are electrocardiogram, electroencephalogram, electromyogram, and electrooculogram. The electrodes used for monitoring these signals are Ag/AgCl and gold, which require skin preparation by means of scrubbing to remove the dead cells and application of electrolytic gel to reduce the skin contact resistance. The gel takes a role of reducing skin contact impedance in the conventional Ag/AgCl electrode and its usage is directly related to the sensitivity. However, the wet conventional Ag/AgCl electrode has some drawbacks such as difficulty in long time monitoring because the gel dries out after few hours and skin irritations. Usually, physiological parameters are monitored over an extended period of time during the patient’s normal daily life to diagnose a disease. In this case, the wet conventional Ag/AgCl cannot be used because of the dry-out of gel. The dry-out of gel increases the impedance between skin and electrode and it is reflected in the poor signal sensitivity. Also noises, such as motion artifact and baseline wander, are added to the biopotential signals as the electrode floats over the electrolytic gel during monitoring. To overcome these drawbacks, dry nanoelectrodes are proposed in this paper where the electrodes are held against the skin surface to establish contact with the skin without the need for electrolytic fluids or gels. The results are presented along with a wireless communication such that the proposed system is ideal for point-of-care diagnosis of the patient at home.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Data flow schematic of the remote patient monitoring system

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Figure 2

Waveforms representing various EEG signals at different frequencies (6)

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Figure 3

Labels for points according to 10–20 systems of electrodes placement (6)

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Figure 4

SEM pictures of a carbon nanotube composite electrode

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Figure 5

SEM pictures of plasma treated carbon nanotube electrode

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Figure 6

Ion beam deposition system

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Figure 7

Vacuum chamber, substrate holder, and ion guns

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Figure 8

Schematic diagram of ion beam plasma treatment

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Figure 9

Fabrication procedure for single layer Au nanowires: (a) Ti/Au layer deposited on a substrate, (b) attachment of polycarbonate membrane, (c) lithography process, (d) cylindrical nanopores opened by UV exposure and developing, (e) nanowires growth, and (f) vertically aligned nanowires after removal of polycarbonate membrane

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Figure 10

SEM image of 2 μm long vertically aligned Au nanowires grown by template method

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Figure 11

Image of the wireless POC system, (a) wireless sensor unit and (b) wireless receiver unit

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Figure 12

Image of EEG electrodes, (a) conventional wet Ag/AgCl electrode, (b) carbon nanotube electrode, (c) plasma treated carbon nanotube electrode, and (d) gold nanowire electrode

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Figure 13

Experiment setup of electrodes testing

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Figure 14

EOG signals with carbon nanotube and wet Ag/AgCl electrodes

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Figure 15

EOG signals with plasma treated carbon nanotube and wet Ag/AgCl electrodes

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Figure 16

Boxplot of two-sample T, (a) wet conventional Ag/AgCl and carbon nanotube (dry powder) electrodes and (b) plasma treated carbon nanotube (dry plasma) and wet conventional Ag/AgCl electrodes

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Figure 17

Plot of biopotential signals with gold nanowire electrodes

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Figure 18

Biopotentials test set up for dry gold nanowire electrodes

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Figure 19

EOG measurements with dry gold nanowire electrodes

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Figure 20

EMG measurements with dry gold nanowire electrodes

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Figure 21

EEG measurements with dry gold nanowire electrodes

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Figure 22

ECG measurements with dry gold nanowire electrodes

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