CNT and Organic FETs Based Two-Way Transducing of the Neurosignals R. Sklyar

Verchratskogo st. 15-1, Lviv 79010 Ukraine, sklyar@tsp.lviv.ua

ABSTRACT

A SuFET based neurotransducer (sensor) with carbon nanotubes (CNT) or PC kind of input circuit for the nerve and neuron impulse has been designed. A nanoSuFET with a high-temperature superconducting channel is introduced into the nerve fibre or brain tissue for transducing their signals in both directions. Pickup coils are implanted into an organism in order to obtain the natural neurosignals from the organs and tissues, also the artificially excited signals to them. On the bases of depicted transducer a combined processor for the natural and artificial information is advanced.

Keywords: neurosignals, SuFET, interface, textile, processor

1 INTRODUCTION The recent achievements in nanoelectronics can be

regarded as a further step in the progress of NS transduction. They give us the possibility to create the most advanced and universal device on the basis of known micro systems. Such a sensor/transducer is suitable for picking up neurosignals (NSs)- nerve and neuronic impulses (Fig. 1)- and transforming it into recognizable information in the form of electric voltage, or a concentration of organic or chemical substances [1]. Moreover, this process can be executed in reverse. Substances and/or voltages influence NSs, thereby controling or creating them (NSs).

Fig. 1 Longitudinal sect ion of an axon showing a few lines of current flow

The advances in nanotechnology are opening the way

to achieving direct electrical contact of nanoelectronic

structures with electrically and electrochemically active subcellular structures- including ion channels, and receptors. Interfacing of nerve cells and field-effect transistors (FETs) is determined by current flow along the electrical resistance of the cell-chip junction. A spectral power density of the junction is 5·10-14 V2/Hz and can be interpreted as Nyquist noise of the cell-chip junction with a resistance of 3 MOhm by measuring the fluctuations of extracellular voltage with a low-noise transistor [2]. The thermal noise allows us to elucidate the properties of cell adhesion and it sets a thermodynamical limit for the signal-to-noise ratio of neuroelectronic interfacing.

2 DESIGN OF THE TRANSDUCER

Proceeding from the previously mentioned difficulties,

including superconducting element of the sensor/transducer into an electric current could be the solution to the problem [3]. Electronic or ionic currents in conductors or axons respectively, passing through the superconducting FET’s (SuFET’s) channel induce the output voltage on its gate (Fig. 2). The method of combining the bioelectric nature of NSs with body-temperature pickup coil (PC) and reverse input of the SuFET device in order to obtain most advantageous biosensor/transducer was recently advanced [4] (Fig. 3). The SuFET is used as a zero-resistance ammeter which converts drain currents into gate voltages.

Among the variety of the organic FET devices [1] there

are majority of them, mainly modifications of nanoFETs, which allow simultaneous processing of a number of NSs directly or from the PC. There are two factors that make simultaneous processing possible. First of all, the sizes of nanoFETs and nanoPCs are in the same order as the transmitting substances of NSs, such as axons and neurons. Secondly, the crossed-nanowire FET or textile (Fig. 4)

Fig. 2 An organic Su FET

and its electrodes

Uout

í

device

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arrays are, in itself, multiinput. The remaining part of FET devices are applicable for serial connection to the said mediums. In addition, some of these FETs can be arranged

in the chain in order to transduce the NSs into different physical and chemical quantities and vice versa [5].

3 COMBINING OF THE NATURAL AND

ARTIFICIAL PROCESSING ABILITIES Multiprocessor data fusion is in effect intrinsically

performed by animals and human beings to achieve a more accurate assessment of the processing environment. The aim of signal processing by the combined artificial-living being multiprocessor system is to acquire complete information, such as a decision or the measurement of quantity, using a selected set of input data stemming to a multiprocessor system- digital data are coming to artificial processor and the rest of information consumes by a neural system of living being. Thereby, a big amount of available information is managed using sophisticated data processing

for the achievement of a high level of precision and reliability.

3.1 Arrangement of the Combined System

It is possible to substitute the microcomputer in an object-oriented problem solution scheme by the natural processing organ- brain or spinal cord. As a result, the software component will be eliminated and the most general characterization of the processing problem in one-coordinate dimensional calculations could be acquired naturally, according to the feedback reaction on the input exposure for calibration, error correction, scaling up or down, range extension, sampling, resolution, etc (see Appendix).

in vivo

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gate

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following external units

Fig. 1. An SFET based biotransducer and its signal behavior

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Fig 3. A neurotransducer as the inclusion of a SuFET device into the nerve fibre:

A- implantation of the whole high-Tc SuFET variant; B and C- tapping of NSs i bio on the external SuFET by implantable wire contacts.

Fig. 4 Technological solutions for textile electronics: a) a ribbon; b) a cylindrical yarn.

a) b)

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Application variety of the novel superconducting, organic and CNT transducers allows us to design processors of the biosignals (nerve, neuronic, DNA, etc.) that transduce them into different quantities, including electric voltage, density of chemical and biomolecules. On the other hand, the said NSs can be controlled vice versa by the applied electrical signals, or bio and chemical mediums [4].

3.2 Application of a Solid-State Electromagnetic (Optical) Transistor

The known ferromagnetic materials have a hysteresis loop. That is why their application do not possible because of ambiguity of characteristic. The device for controlling the magnitude of optical flux by the application of an electromagnetic (EM) field is based on a ferroelectric (FE) or ferroelectromagnetic (FEM) polarizer that allows the rotation of the polarizing plane according to a hysteresis loop [6]. Besides, the controlling possibility of the known ferromagnetic and FE devices is substantially restricted by an ambiguous part of a hysteresis. That is why it is possible only switching of an EM flux between two stages.

The invented transistor consists of FE or FEM processing crystal, source of an EM energy, and the analysing element (Fig. 5). Control of an EM flux or OB has been carried out by splitting them on two parts: a passed one through the processing body and reflected part by this body. An EF or MF is applied by the carbonic nanotubes (CNT) or polymer nanowires to the crystal which is rotating a polarization angle of EM flow or OB. The electrical transport between the contact metal and the nanotube occurs along the entire nanotube under the contact electrode. This suggests that the transfer length, which is defined as the distance required for current to flow into or out of the contact electrode is thought to be less than 50 nm [7]. This angle is rotated according to the linear part of a FE or FEM crystal’s characteristic. The amplified signal is analysed in the units of a polarization angle. The reflected part is used as polarization P2(φ) (Fig. 5) for creating the logical (optical and magnetic) elements “AND”, “OR”, and “NOT”. This device is switching or amplifying of EM flow and OB as by magnitude, as well as by an angle of polarization.

As a result, it will be possible to overcome the said disadvantages of the known devices, namely: 1) to raise the fast-action up to the maximal possible- the speed of spreading an electromagnetic (optical) wave; 2) to reduce the noise level in an amplified signal at the expense of using the material with a unique fashion amplifying (without a hysteresis) performance- without the internal mechanical transformations; 3) to improve an ease of manufacture by using of printing nanotechnologies and expulsion of an additional optical planes or mirrors.

Opt rev

Fig. 5 An Electromagnetic Transistor based on CNT

Opt trans

Opt in

+ N

S _

P2(φ)

P1(φ)

Ferro-el/magn

Exploitation of the parallel input to multiprocessor allows determination of space and time dynamics of NSs in the nerve fibre and neurons and also the amplification of output signal Uout by multiplying the concentration of molecules according to a number of input NSs. After the implantation of parallel SuFET(s) or optical transistors, the averaging or summation of this dynamic among the whole flow network, nerve fibre or neurons is possible.

REFERENCES

[1] R. Sklyar, “Superconducting Organic and CNT FETs as a Biochemical Transducer”, ISMCR 2004: 14th International Symposium on Measurement and Control in Robotics, NASA Johnson Space Center, Houston, Texas, IEEE (ISMCR), section 24, (13 pages), 2004.

[2] F. Patolsky, B. P. Timko, G. Yu et al., Detection, Stimulation, and Inhibition of Neuronal Signals with High-Density Nanowire Transistor Arrays, Science 313 (2006) 1100–1104.

[3] R.Sklyar, Superconducting Induction Magnetometer, IEEE Sensors Journal, April 2006, Vol. 6, Iss. 2, pages 357- 364.

[4] R. Sklyar, Sensors with a Bioelectronic Connection, IEEE Sensors Journal (Special Issue), May 2007, Vol. 7, Iss. 5, pp. 835-841.

[5] R. Sklyar, The Microfluidic Sensors of Liquids, Gases, and Tissues, Journal of Automation, Mobile Robotics and Intelligent Systems (JAMRIS), 2007, No. 2, pp. 20-34.

[6] R. Sklyar, Patent UA #76691 "The control method of the electromagnetic flow intensity and amplifying elements on its bases”, Bull. 9, 2006.

[7] Yo. Nosho et al., Evidence of Edge Conduction at Nanotube/Metal Contact in Carbon Nanotube Devices, Jap. J. of Appl. Phys., vol. 46, 2007, pp. L474–L476.

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A Combined Processor for the Natural and Artificial Information.

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Processor

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synthesized solution

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analytical inform ation [Su(O)FETTr]-1

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voltage signal

current signal

[Su(O)FETTr]-1

Su(O)FETTr

*Su(O)FETTr- supercond. (organic) field-effect transistor based transducer

Appendix

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