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УДК 542.816:615.47
DEVELOPMENT OF PRODUCTION TECHNOLOGY OF ELECTRODES FOR ELECTRICAL NEUROSTIMULATION BY USING TRACK MEMBRANES
Vladimir Valentinovich TROFIMOV1, Dmitriy Yurevich KUKUSHKIN1, Aleksandr Mikhaylovich VASILEV1, Ivan Aleksandrovich ARKHIPUSHKIN2, Vladimir Semenovich KUBLANOV3, Mikhail Vladimirovich BABICH3, Anton Yurevich DOLGANOV3, Vadim Maratovich GADELSHIN3
1MATI - Russian State Technological University named after K.E. Tsiolkovsky 121552, Moscow, Orhanskaya str., 3
2 Institute of Physical chemistry and Electrochemistry named after A.N. Frumkin of RAS 119071, Moscow, Leninky av., 31, bldg. 4
3 Ural Federal University named after the first President of Russia B.N. Yeltsin 620002, Ekaterinburg, Mira str., 19
The original technology of electrode production with track membrane materials for electrical neurostimulation has been described. It has been shown that the technology allows one to produce conducting structures with gas- and water-permeability in places of unfilled pores by metal. The created electrodes also have antiseptic properties.
Keywords: track membranes, electrical stimulation electrode, electrical neurostimulation, antiseptic.
Nowadays, multielectrode systems are applied in promising devices for transcutaneous electrical neurostimulation. These systems can be installed in the neck region [4] and on the language [7]. The electrodes in these systems must ensure the reliability and convenience of their fixation on the patient skin during the whole period of the treatment process.
It is necessary that the base material for the electrode have the following properties: it must be biologically neutral; it must be able to conduct air; it should be durable and resistant to sterilization techniques used in healthcare; it must provide an electrochemical resistance to current flow and have mechanical stability. Electrodes may be wetted with a conductive gel to ensure long-term therapy. The cost of the electrodes required for electrical neurostimulation should be reduced as the tightening of
the requirements for the sanitary hygiene leads to the transition to the disposable electrode system.
Thus, the next task occurs: a mass production of multi-electrode system with narrow-width electrically conductive bands with a width from 0.1 to 0.5 mm and a length up to several tens of mm, which provide resistance not greater than 100 Ohm and stability of electrical parameters. The topologi-cal structure of such system may be quite difficult. The requirements to geometrical stability depend on geometry of neural paths and may be expressed by deviation from bits of mm.
PROBLEM AND METHODS ANALYSIS
FOR ITS SOLUTION
Obtaining of conductive structures for different applications on materials, fastened on human body
Trofimov V.V. - engineer, e-mail: tvv@jinr.ru
Kukushkin D.Yu. - assistant, e-mail: skyline34@nxt.ru
Vasilev A.M. - docent, e-mail: vasal2@yandex.ru
Arhipushkin I.A. - researcher, e-mail: arhi90@mail.ru
Kublanov V.S. - professor, e-mail: kublanov@mail.ru
Babich M.V. - assistant, e-mail: m.v.babich@urfu.ru
Dolganov A.Yu. - junior researche, e-mail: anton.dolganov@urfu.ru
Gadelshin V.M. - junior researcher, e-mail: gadelshinvm@mail.ru
or on dress, is considered as a goal of many strategies like «smart textile». Processes of cloth metallizing and a field of their applicability are offered in a number of papers [8]. Actually, it is impossible to form electrodes on this base and with presented above characteristics because of high surface resistance. The complexity of electrode production, based on woven or not-woven materials via spraying, is caused by shading of fiber pieces. This fact is noted in [2], however, with the proposed technology it is not possible to get contact points with prescribed geometry. That has been examined as a part of current work. Titanium coating was applied by magnetron spraying on different cotton and synthetic clothes, not-woven materials included. The obtained coatings have had a resistance about 10 kOhm. One more possibility is the technology based on carbon nanotubes [3, 8], but this technology is not available for us.
RESULTS AND DISCUSSION
It seems that it is necessary to find a material for the electrodes formation that would be porous, has a smooth surface, has small coefficient of elongation. Such properties are combined in track membranes. [6]. In experiment the PETF membrane with a thickness of 20 (im, a pore diameter of 1 (m and a density about 107 pores per cm2 were used. This membrane characteristics were chosen from consideration of balance between the porosity of 10 % and a mechanical robustness. As a basic material, two types of conductive layers were investigated: titanium nitride and copper. Titanium was deposited by magnetron (or arc) sputtering in the uncooled drums. The thickness of spaying varied from 0.05 to 1 (m. The total direct-current resistance of samples, with sizes of 120 x 30 mm and 50 x 50 mm, was monitored. Values of resistance were in a range from 101 to 102 Ohm. The surface resistance was measured by four-point method on the booth and by averaging of value over the sample surface. Four modes of spraying were investigated. In Table we present data of minimal and maximal resistances for different spraying modes.
Table
Resistance of samples for different spraying modes
Spraying mode Resistance, Ohm
min max
1 170.384 191.219
2 73.617 86.581
3 53.245 61.116
4 12.501 13.427
Presented in Table characteristics are satisfactory for the area of the electrode, but are insufficient for lead wires. In addition, it is complex to provide transition from the contacts of sputtered titanium to conductive lines, that are associated with the source of the current pulse field of the electrical neu-rostimulator, in the mask technology of the electrode formation. On the one hand, the usage of materials with high conductivity (such as noble metals) is precluded by economic considerations. On the other hand, the formation of conductors with copper is unacceptable for hygienic reasons. Therefore, two-layer base material is proposed that has the conductive layer of deposited copper, with a coating of titanium, which provides biocompatibility.
The methodology of copper plating on a porous track membrane consists of several stages: preparation, sensitization, activation, metallizing. At preparation stage, the coated material strip degreased in acetone and washed with twice-distilled water in an ultrasonic bath. Sensitization of surface was carried out in an acid solution of tin chloride SnCl2. Material withstood a few minutes in the solution. After that, material was washed with warm water for the acceleration of the hydrolysis of the adsorbed salt. Activation of non-conductive surfaces was carried out in solution of palladium chloride PdCl2. This was followed by the stage of metal application. In this case, a tartaric solution of electroless copper was used, which is composed of copper sulfate, sodium potassium tartrate, potassium hydroxide. The electrolyte solution is made of recrystallized salt CuSO45H2O then tartrate KNaC4H4O6-4H2O and KOH were inputted. Formaldehyde solution was used as the reducing agent. During the reduction, bubbles of hydrogen is extracting, therefore, solution was being intermixed quietly to reach a coating uniformity. After precipitation of the coating, samples were washed off by water and were dried off in a chamber drier for one hour under temperature of 55 °C.
Standard adhesion test (the «scotch tape»-test) has showed that the coating is durable. The measurement of electric resistance has given values lower than 10-2 Ohm between randomly chosen points on the sample. Resistance values are of the same order between two sides of the sample. To understand a mechanism of adhesion and closure between layers, a microscopy of the sample via the electron microscope Hitachi TM 3000 has been carried out. In Fig. 1 front image of electrodes contact surfaces is shown. One can note that pores are not closed. The copper layer does not have cracks and spaces, thus, the attainment of steady electrical contact is ensured.
In Fig. 2 image of a side surface for sliced up sample by cutting edge is presented. Fig. 2 explains
a nature of adhesion. It is caused by the molecular force of coupling. On the other hand, it can be seen that individual pores are filled with metal. Their quantity is not too big; therefore, they cannot be a reason of adhesion. They are links between layers. As two metal-filled pores out of dozen can be clearly noticeable on the presented image, than among 107 pores per 1 cm2 there will be significant number of filled pores to ensure an electrical contact.
The proposed process can be favorably distinguished from tries of develop a multi-stage technology [1, 5], where a glue-free mounting of metallic layer by means of a forming of «anchors» is used. «Anchors» are obtained by filling of intersectional channels of tracks.
Track membrane material remain gas- and water-permeable if in the process of precipitation, a metal does not fill pores. The material with such properties may be interesting not only for production of the electrical neurostimulation electrodes, but also for production of elastic cables, as the crack on the one side of path does not lead to contact breaking. Copper samples have given a resistance in a range of 10-2-10-3 Ohm. These values are sufficient for the stated applications.
It is proposed to use a process of laser engraving the material to form the electrode geometry. Prior to the engraving it is advised to glue material to the fabric substrate. This provides mechanical strength.
Also, it seems appropriate to impregnated the fabric which is attached to the electrode with the silver nanoparticles.
Silver nanoparticles have sustained bacteriostatic effect on more than 650 kinds of bacteria and viruses, while maintaining the DNA structure integrity. As it is known, the nanometer-sized particles have several unique properties. They carry a positive charge, and their electrical and physicochemical properties are determined by the size of the nanocluster. Therefore, na-noparticles positioning on the electrode surface is possible by electrophoresis. Reaching the electrode, the particles coalesce and lose their charge, resulting in a colloidal solution coagulates on the surface of the material. The unit and the process of electrophoresis impregnation was also trialed on test material - carbo-xylic tissue. This choice has been made for reasons of control of the deposition process by electron microscopy. The image of carboxylic tissue with impregnated silver nanoparticles is presented of Fig. 3.
CONCLUSION
Presented in the paper results describe features and peculiarities of the electrical neurostimulation electrodes production technology. The track membrane material application allows one to produce
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Fig. 1. Microphotography of front view from the side of contact surface of electrodes
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Fig. 2. Microphotography of cross-sectional view of the slited sample
Fig. 3. Modified carbon fiber with an Ag nanoclusters
industrial technologies of manufacturing conducting structures for different spheres of application.
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3. Hu L., PastaM., Mantia F.L. et al. Stretchable, porous, and conductive energy textiles II Nano Lett. 2010. 10. (2). 708-714.
4. Kublanov V.S., Petrenko T.S., BabichM.V. Multi-electrode neurostimulation system for treatment of cognitive impairments II Engineering in Medicine and
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7. Wildenberg J.C., TylerM.E., Danilov Y.P. et al. Electrical tongue stimulation normalizes activity within the motion-sensitive brain network in balance-impaired subjects as revealed by group independent component analysis II Brain Connect. 2011. 1. (3). 255-265.
8. Zhou H., Lu Y., Chen W. et al. Stimulating the comfort of textile electrodes in wearable neuromuscu-lar electrical stimulation II Sensors. 2015. 15. (7). 17241-17257.
РАЗРАБОТКА ТЕХНОЛОГИИ ИЗГОТОВЛЕНИЯ ЭЛЕКТРОДОВ ДЛЯ НЕЙРОЭЛЕКТРОСТИМУЛЯЦИИ С ИСПОЛЬЗОВАНИЕМ ТРЕКОВЫХ МЕМБРАН
Владимир Валентинович ТРОФИМОВ1, Дмитрий Юрьевич КУКУШКИН1, Александр Михайлович ВАСИЛЬЕВ1, Иван Александрович АРХИПУШКИН2, Владимир Семенович КУБЛАНОВ3, Михаил Владимирович БАБИЧ3, Антон Юрьевич ДОЛГАНОВ3, Вадим Маратович ГАДЕЛЬШИН3
1МАТИ - Российский государственный технологический университет им. К.Э. Циолковского 121552, г. Москва, ул. Оршанская, д. 3
2 ФГБУНИнститут физической химии и электрохимии имени А.Н. Фрумкина РАН 119071, г. Москва, Ленинский пр., 31, корп. 4
3 Уральский федеральный университет им. первого Президента России Б.Н. Ельцина 620002, г. Екатеринбург, ул. Мира, 19
Описывается оригинальная технология изготовления электродов для нейроэлектростимуляции с применением материалов на основе трековых мембран. Показано, что технология позволяет создавать проводящие структуры и обеспечивать газо- и водопроницаемость в местах, в которых металл не закрывает поры, а также иметь антисептические свойства.
Ключевые слова: трековые мембраны, электроды для электростимуляции, нейроэлектростимуляция, антисептик.
Трофимов В.В. - инженер, e-mail: tvv@jinr.ru Кукушкин Д.Ю. - ассистент, e-mail: skyline34@nxt.ru Васильев А.М. - доцент, e-mail: vasal2@yandex.ru Архипушкин И.А. - научный сотрудник, e-mail: arhi90@mail.ru Кубланов В. С. - профессор, e-mail: kublanov@mail.ru Бабич М.В. - ассистент e-mail: m.v.babich@urfu.ru
Долганов А.Ю. - младший научный сотрудник, e-mail: anton.dolganov@urfu.ru Гадельшин В.М. - младший научный сотрудник, e-mail: gadelshinvm@mail.ru
