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Application of electrostatically actuated carbon nanotubes in nanofluidic and bio-nanofluidic sensors and actuators Mir Masoud Seyyed Fakhrabadi1*, Abbas Rastgoo1, Mohammad Taghi Ahmadian2 1
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran 2
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
Abstract The paper investigates the effects of fluid flow on the static and dynamic behaviors of electrostatically actuated carbon nanotubes using nonlocal elasticity theory. The influences of various parameters of fluid flow including fluid viscosity, velocity, mass and temperature on the mechanical behaviors of the carbon nanotubes under static and step DC voltages are studied using this theory. The results computed from the nonlocal elasticity theory are compared with those estimated using the classical elasticity theorem and the outcomes demonstrate the applicability of the electrostatically actuated carbon nanotubes as nano sensors and nano actuators in nanofluidic systems. The nanosystem can be potentially applied in precise nanoscale drug delivery as well as other bio-nanofluidic processes. Keywords: Carbon nanotubes, Nonlocal elasticity theory, Nanosensors and nanoactuators, Nanofluidics, Bio-nanotechnology.
*
Corresponding author Email: mfakhrabadi@ut.ac.ir msfakhrabadi@gmail.com ; Tel/fax: +98 935 5928477
1- Introduction Fluid flow through the nano pipes and nano channels can possess various applications in nanotechnology ranging from nano medicine to nano engineering [1-3]. Carbon nanotubes (CNTs) are excellent options for these purposes due to their extraordinary mechanical properties, chemical and thermal stability, and hollow geometries. For example, they can be served as hydraulic fluids in support platforms or carry reactant molecules into reaction chambers [4]. Furthermore, the CNTs have potential usage as cancer therapy devices or nano-vessels for conveying and storing fluids and drug delivery in bio-nanotechnology [5]. As an example, nano pipes that act like tiny straws deliver medicines to a person’s bloodstream or to a highly specific location in the body. According to the potential applications of the CNTs conveying fluid, it is obvious that the effects of fluid flow on the mechanical behaviors of the CNTs should be scrutinized. Of course, the mechanical behaviors of the CNTs conveying fluid were studied before. But, applying electrostatic actuation to the nanosystem for the reasons described in the following paragraphs and studying the effects of nonlocality on its behavior has not been investigated yet. Yoon et al may be was the first ones studied the flutter instability of the CNTs resulted from the fluid flow [6]. They presented the natural frequencies and damping of the CNT for various fluid velocities. Their work had some shortages that were compensated by Wang and Ni [7]. They comprehensively investigated the mentioned phenomena. In another research, they studied the effects of viscosity on the instability of the CNTs conveying fluid flow [8]. The authors of [7, 8] applied the well-known Euler-Bernoulli beam model in their researches but Chang and Lee used the Timoshenko beam model considering the rotational inertia and shear deformation to
investigate the effects of internal fluid flow on the transverse vibration [9]. They reported the natural frequencies of the system for different aspect ratios. Despite some studies regarding the effects of fluid flow on the static and dynamic behaviors of the CNTs that some of them reviewed above, controlling the flow was not investigated in detail. Only some limited number of papers mentioned it very basically through reporting the rudimentary conceptual designs of the CNTs as nano valves [10-12]. It is clear that every fluidic system and piping should have effective and applicable controlling devices such as valves, flow meters, pressure sensors, viscometer, densitometer, etc. The nano fluidic systems in gereral and bio-nanofluidic systems in particular are not definitely exceptions of this fact. The development of such systems for the fluid flow through the nanotubes is exactly one of the main goals of this research. In spite of invaluable ideas behind the designs presented in [10-12], they may not have reliable performance in the real systems especially in those requiring very fast actuation and response due to their extremely slow responses. This paper tries to develop a more applicable technique to apply the CNTs as the nano valves as well as some other fluid controlling devices such as viscometer, densitometer and velocity sensor. The electrostatic actuation of the CNTs conveying fluid can help the mentioned roles. In electrostatic actuation, two conductive electrodes parted from each other with an initial gap are applied an electrical potential difference. In general, one of the electrodes is fixed and the other one is movable (Fig. 1). Positive and negative charge distributions on the electrodes resulted from the applied potential difference leads to attract the movable electrode towards the fixed one.
ď&#x20AC;&#x2026;ď&#x20AC;&#x201A; ď&#x20AC;&#x201A;
This deflection is similar to the deflection shown in Fig. 2. As shown in Fig. 2, by applying an external transverse force to a constrained CNT conveying fluid, a critical section deforms so that it does not allow the fluid flow to pass or can confine it [11, 13]. The level of confinement is a function of the applied force and the resultant deformation. When the applied voltage reaches to a threshold value, the CNT does not endure the attractive force resulted from the electrostatic actuation and interatomic interactions anymore and suddenly drops on the fixed electrode. In the discussed instability, the local buckling of the CNT displayed in Fig. 2 can be so that it can confine the fluid stream completely. This concept is applied for nano valve application of the CNTs. Obviously, the fluid flow affects the mechanical properties of the CNTs and consequently the pull-in voltage is a function of the fluid parameters. Thus, it can be applied as a nanofluidic sensor and can sense the various fluid parameters via sensing the alteration in the instability voltage. In this paper, we are going to investigate the applicability of the proposal suggested in the above lines using the nonlocal theory (NLET) proposed by Eringen and Edelen [14. According to this theory the stress at a reference point x in an elastic body not only is a function of the strain at the point but also relates to the strains at every point of the body [15]. The NLET is applied due to failing or less accuracy of the classical elasticity theories (CETs) in predicting the mechanical behaviors of the micro and nano structures [16, 17]. Numerical solution techniques are always helpful in analyzing the governing complex equations [18, 19] and are going to be applied in this paper.
2- System description
Solid State Communications 157 (2013) 38–44
Contents lists available at SciVerse ScienceDirect
Solid State Communications journal homepage: www.elsevier.com/locate/ssc
Molecular dynamics simulation of pull-in phenomena in carbon nanotubes with Stone–Wales defects Mir Masoud Seyyed Fakhrabadi a,n, Pooria Khoddam Khorasani a, Abbas Rastgoo a, Mohammad Taghi Ahmadian b a b
[13]
College of Engineering, School of Mechanical Engineering, University of Tehran, Tehran, Iran Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history: Received 7 September 2012 Received in revised form 11 December 2012 Accepted 18 December 2012 by Z. Tang Available online 23 December 2012
This paper deals with investigation of deformations and pull-in charges of the cantilever and doubly clamped carbon nanotubes (CNTs) with different geometries using molecular dynamics simulation technique. The well-known AIREBO potential for the covalent bonds between carbon atoms, LennarJones potential for the vdW interaction and the Coulomb potential for electrostatic actuation are employed to model the nano electromechanical system. The results reveal that longer CNTs with smaller diameters have smaller pull-in charges in comparison with shorter CNTs possessing larger diameters. Furthermore, the pull-in charges of the doubly clamped CNTs are higher than the pull-in charges of the cantilevered CNTs. Another important matter discussed in this paper is the effects of Stone–Wales defects on the pull-in charges. The results show the reduction of the pull-in charges in the presence of Stone–Wales defects in the nano system. & 2012 Elsevier Ltd. All rights reserved.
Keywords: A. Carbon nanotubes B. Molecular dynamics C. Stone–Wales defect D. Pull-in phenomena
1. Introduction Carbon nanotube (CNT) can be considered as one of the most influential and applicable nanostructures in the nano systems. Since its discovery by Ijima in 1991, many researchers and scientists with different disciplines have started to study its properties using theoretical and experimental techniques. In many aspects, especially in engineering fields, the studies have revealed that the CNT have exceptional characteristics. This fact has resulted in applying the CNTs in various engineering applications with the focus on the mechanical and electrical nano systems. Fakhrabadi et al. applied molecular mechanics method to study the vibrational properties of the CNTs with different geometries and boundary conditions [1]. They combined the mentioned method with the artificial neural networks in order to investigate the natural frequencies of the unmodeled CNTs. They proved that the proposed scheme could predict the natural frequencies with good agreement with the real values. In another research, Rossi and Meo computed the Young’s modulus, ultimate strength and strain of the single-walled CNTs using molecularmechanics technique [2]. They applied nonlinear and torsional
n
Corresponding author. Tel./fax: þ 98 935 5928477. E-mail addresses: msfakhrabadi@gmail.com, mfakhrabadi@ut.ac.ir (M.M.S. Fakhrabadi). 0038-1098/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ssc.2012.12.016
spring elements to evaluate the mentioned properties as well as the tensile failure. Chowdhury et al. applied molecular mechanics method to analyze the vibrational properties of the zigzag and armchair CNTs. The natural frequencies and their corresponding mode shapes were presented in their paper for different geometries [3]. In addition, Joshi et al. investigated the effects of chiralities and atomic vacancies on the vibrational behaviors of the nanoresonators based on the CNTs via application of the molecular mechanics approach [4]. They studied the natural frequencies of the CNTs with different chiralities and atom vacancies in order to propose a more real model for the designers of the CNT-based devices. The vacancies imposed some variations in the natural frequencies. In another paper, they conducted similar research on the effects of pinhole defects on the vibrational characteristics of the CNTs [5]. Molecular mechanics method that is an effective technique in nanomechanics engineering was used in some other studies [6–9]. Another effective tool to investigate the physical and chemical properties of the nanostructures in general and carbon nano materials in particular is molecular dynamics applied in this paper. Hao et al. studied buckling of defective CNTs under axial compression by molecular dynamics simulation [10]. The densities of the defects and their positions played important roles in the final results. The outcomes revealed that vacancy defects possessed significant effects on the critical buckling loads of the CNTs. Wang et al. simulated the twist of the CNTs using molecular dynamic technique [11]. The ultimate twist angle per unit length
[1] 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: processor
neurosignals,
1
SuFET,
interface,
textile,
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).
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 signalto-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.
U out
í Fig. 2
Fig. 1 Long itudinal 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
An organic Su FET device and its electrodes
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)
in the chain in order to transduce the NSs into different physical and chemical quantities and vice versa [5].
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
A
myelin c hannel ‘s
nerve NI impulse
i bio
Vg Vout
ionic currents
SuFET SFET axons
PC
B
°
gate
°
i bio
R
°
E transmit0
receiving C unit
~
ting unit
in vivo
Draine
visualization and memory units
C0
L
SuFET
H
° °
° Gate
Vo u t
Source
(Bio)Telemetr y
following external units
Cryostat
Shie ld
Fig. 1. An SFET based biotransducer and its signal behavior
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.
a)
b)
Fig. 4 Technological solutions for textile electronics: a) a ribbon; b) a cylindrical yarn.
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 onecoordinate 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).
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 P2(φ)
N
+
Opt
trans
Ferro-el/magn P1(φ)
Opt in
_
S
Fig. 5 An Electromagnetic Transistor based on CNT 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.
Appendix
A Combined Processor for the Natural and Artificial Information.
n a t u r a l
En = kT / gDS ⋅ γ noise
sensing signals
VGS =
jπ µ 0 S eq h ω T (Q G ) f eI 0 z c
Vout Knerv e= i
H
[Su(O)FETTr] -1
* Su(O)FETTr
voltage signal
AND
output
OR
interface
co mlex p ro blem
input
B ra in, spin. co rd
synthesized solutio n
Proc es s or analytical inform ation
U ncNo iWs e = n 4 k T / Q
[Su(O)FETTr] -1
Vg =
current signal
Su(O)FETTr
j h ω T (Q G ) ID 2 eI 0
K cNW =
V out V sup Q + i
a r t i f i c i a l *
Su(O)FETT r- supercond. (orga nic) field-effect transistor based transduc er
[2]
Hindawi Publishing Corporation Journal of Sensors Volume 2009, Article ID 516850, 20 pages doi:10.1155/2009/516850
[3]
Review Article A Complex of the Electromagnetic Biosensors with a Nanowired Pickup Rostyslav Sklyar Verchratskogo st. 15-1, Lviv 79010, Ukraine Correspondence should be addressed to Rostyslav Sklyar, sklyar@tsp.lviv.ua Received 29 April 2009; Accepted 24 September 2009 Recommended by Joan Daniel Prades The proposal to measure the biosignal values of different origins with advanced nanosensors of electromagnetic quantities is justified when allowing for superconducting abilities of the devices. They are composed in full-scale arrays. The said arrays can be both implantable into ionic channels of an organism and sheathed on the sources of the electromagnetic emanation. Nanowired head sensors function both in passive mode for picking up the biosignals and with additional excitation of a defined biomedium through the same head (in reverse). The designed variety of bio-nanosensors allow interfacing a variety of biosignals with the external systems, also with a possibility to control the exposure on an organism by artificially created signals. The calculated signals lies in the range of −5 to 5 V, (7/0) · 1017 /cm3 molecules or magnetic beads, 2/10 pH, and stream speed 3 · 10−3 /102 m/s, concentration of 1030 /1024 molec/cm3 . The sensitivity of this micro- or nanoscope can be flow 10−5 /10 m/s, and haemoglobin √ −4 estimated as HJ = 10 (A · m/ Hz) with SNR equal to 104 . The sensitivity of an advanced first-order biogradiometer is equal to √ 3 fT/ Hz. The smallest resolvable change in magnetic moment detected by this system in the band 10 Hz is 1 fJ/T. Copyright © 2009 Rostyslav Sklyar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction. The Nanowires Based Elements and Devices Carbon nanocoils (CNCs), are a new type of promising nanomaterials. These have attracted considerable attention because of their potential applications, for example, parts for nano or micro-electromechanical systems, electromagnetic (EM) wave absorbers, reinforced composites, nanosolenoids, and field emission devices. Furthermore, the detailed analyses of the microscopic structures of the catalyst particles are very interesting subjects for future studies. These thin and highly crystallized multiwalled CNCs would find wide applications in new nanotechnology [1]. CNCs with nanometerscale size are attracting much because of their peculiar helical morphology, aligned toward the electric field, and form a small aggregation of a CNC chain by the dipolar interaction of CNCs [2]. Self-assembled molecular nanowires (NWs), achieving four-level switching in a multiwire transistor and demonstrating their suitability for the production of multilogic devices, have been studied. Wires were composed of a single crystal, allowing good electrical transport with low resistivity.
Field-effect transistors (FETs) with single- and doublewire channels were fabricated to give some indication of the potential application of the molecular wires. Appropriate molecular design and control of interfacial interactions lead to single crystalline wire growth with an extensive πstacking motif. The single- and doublewire transistors were fabricated, successfully using needle probes to apply gate voltage [3]. With the latter, a double top gate configuration enabled independent control of the drain current through each wire and enabled modulation to four different values by turning gate voltage on and off. Resistivity measurements of an individual molecular wire indicate that the structural features are advantageous for electrical transport. The first metal-semiconductor FET was fabricated with a self-assembled, planar gallium-arsenide NW channel (Figure 1). Compound semiconductor NWs, such as gallium arsenide, are especially desirable because of their better transport properties and versatile heterojunctions. The selfaligned orientation of the NWs is determined by the crystal structure of the substrate and certain growth parameters. By replacing the standard channel in a metal-semiconductor
16
Journal of Sensors
without the need for specific magnetic properties. The principle is attractive for the development of passive sensors operating in environments with limited accessibility or incompatible with active electronics [36]. Realization of our innovation is proposed by the use of ambient natural MF which regards DC or stationary [37]. The employed PCs for creating and/or receiving of MF are made from the superconducting material. As a result, the hard magnet of an electrodynamical transducer is replaced by the natural MF, and Meissner effect displaces this MF from any superconductor PC or continuous section, because any change of the ambient MF vortical currents arises in a superconductor which compensates for these changes, according to the Lenz law. Some merits of this method reside in reducing the device’s mass and energy consumption due to functioning in the passive mode. It is that a superconducting membrane is oscillating into the ambient MF. In such arrangement, the sensitivity of transducing of the acoustical signal into electrical one is rising. Because, of the virtual absence of noises in the superconducting element. Electro-acoustical device provides the transducing of the membrane oscillations in an electrical current I and in reverse to acoustical wave (Figure 25). During this transducing a value of PC’s I is defined by µ0 µef Wπd2 BWπd2 H= , (20) 4L 4L where Wis total turn number of solenoid. On the conductor with a current I in MF, B is affecting the force: I=
F = BlI.
(21)
The ratio of this force to a plane of a surface of membrane S gives a pressure of an acoustical wave on the membrane or, in reverse, the value of acoustical pressure of the membrane: " BlI B2 lWπd2 ! = H/m2 . (22) S 4LS Taking into account the standard threshold sound pressure p0 = 2 · 10−5 Pa, the absolute value of a sound pressure is defined as B2 lWπd2 . (23) A = 20lg 4LSp0
p=
The second advanced mechanism for generation of the acoustic oscillations is using of Meissner effect, which is implemented by closed contact of a superconducting PC (Figure 25(a)), during the rising of vortical currents Ivort in the plane of the superconducting membrane (Figure 25(b)). Figure 26 presents the dependence A from B in the earth MF for the value parameter’s: d = 0.2 m, L = 0.2 H, S = 0.04 m2 . Suppling of a signal into the membrane and its picking up are carried out by SuFET. A linear dependence between an amplitude of oscillation A of the membrane and I of NWPC examines to the value I which is equal to the critical current I0 of a superconductor. After reaching this level, the current I0 , and respectively also the transducing ability, is significantly decreasing due to going of a (high-Tc ) superconductor into the resistive state.
6. Results. The Design Variants of NWPCs The variety of applications of the novel superconducting, organic and CNT FETs with NWPCs allows us to design transducers of BSs (electronic, nerve, DNA, etc.). They transduce BSs into different quantities, including electric voltage, and the density of chemical and biomolecules. On the other hand, the said BSs can be controlled by the applied electrical signals, or bio and chemical mediums. The described SuFET based sensors/transducers (SuFETTrs) designed on the basis of organic and nano SuFETs are suitable for describing the wide range of BS dynamical parameters (see Table 2). The table illustrates that a serial connection of the external NWPCs allows us to gain some integrated signal. The whole sensing or electronic control or nerve impulse (NI) spreads along the number of axons of the nerve fibre, the amount of ions passing through the NWPCs and the generalized BS passing through one or both spirals of DNA. When SuFET channel(s) are implanted into the tissue or process, we can acquire more precise data about the frequency distribution of NIs, volume distribution of ionized molecules and detecting activity of individual nucleotides. The preliminary calculations confirm the possibility of broadening the SuFETTr’s action from MF to the biochemical medium of the BSs [13]. The main parameters of these BSs can be gained by applying the arrangement of the SuFETTr(s) to the whole measurement system. Dual directional function of SuFETTr enables decoding of the BS by comparing the result of its action on some process or organ, by using a simulated electrical or biochemical signal after reverse transducing through the SuFETTr(s). Furthermore, this decoded signal will provide a basis for creating feedback and feedforward loops in the measuring system for more precize and complete influence on the biochemical process. The described biosusceptometer or nano-microscope is designed on the basis that EMTMs are suitable for investigating both the structure of organic objects and comparing analysis (see Table 3). The strings of the table illustrate, that investigations of biological surfaces are performing according to the surface integrals for a biosusceptometer and nanomicroscope moduluses, respectively. The surface gradients are being acquired by finding the difference between the respective values of I1 or I2 . The same is applied to the investigations of biological volumes V1 and V2 as the double and triple integrals, respectively. The next two strings are explaining the bounds on the possible spreading of the said method. Exploitation of the parallel input to SuFETTr allows determination of space and time dynamics of BSs in the nerve fibre and neuronic synapse, also the amplification of the output signal Uout by multiplying the concentration of molecules according to a number of input BSs. After the implantation of parallel SuFET(s), the averaging or summation of this dynamic among the whole neural network, nerve fibre or neuronic synapse(s) is possible.
Journal of Sensors
17 Table 2: Dependence of the received BS parameters on the mode of SuFETTr’s functioning. Mode Serial
Medium External !
ibio = 1 contr. or sens. impuls.
NI
Molecules
DNA
!
BSs → bio and chem. molec. Propagation of BS along DNA’s spirals
Parallel Implantable ibio = ibio ( f1 ) + ibio ( f2 ) + · · · + ibio ( fN ) Variation of BSs → concentr. of molec. Decoding the BSs of nucleoted recognition
External dibio /dt, dibio /dx "
BSs = 1 type of molec. Space and length dynamic on both spirals
Implantable ibio = 1 network or 1 fibre " " BSs = bio and chem. molec. "
4 nucleoteds → 4 outputs
Table 3: Dependence of the received structure parameters on the mode of functioning—a biosusceptometer or nano-microscope. Object
Surface Volume
Device Biosusceptometer modulus I1 =
!!
S
f (x, y, z)ds
V !!1 = S f (x, y)dx d y
Structure level
Investigation of sheath (envelopes) of organs
Object (body) level
Investigation of homogeneous organs or tissues
Nano-microscope modulus I2 = !! S f (x, y, z)dx d y V !!!2 = V f (x, y, z)dv Investigation of the inside structure of the organs and tissues Investigation of inhomogeneous organs or tissues
Biosusceptometer gradient
Nano-microscope gradient
∆I1 = I1" − I1""
∆I2 = I2" − I2""
∆V1 = V1" − V1""
∆V2 = V2" − V2""
Comparing investigation of the organ’s or tissue’s areas Comparing investigation of the homogeneous organ’s or tissue’s areas
Differential investigation of the twin (pair) organs or tissues Differential investigation of the inhomogeneous twin (pair) organs or tissues
Table 4: Measuring effects (values) and the relative nano-bio-sensors (for interfacing). NW element
Physical value Ionic currents FE/FEM Magnetic induction MHD/MGD Acoustical oscillations
SuFET channel
PC(s)
EC
Superconducting membraine
NIimpl
NIext
NIcontr
NIimpl
EMTM
EMTM
EMTM
Acoustical EMTM
NIcontr
SIM
NMSc
Noise absorb.
Gaseous FM
Volume FM Acoustical transducer
Active FM
Acoustical FM transd. and loudspeak.
—
Loudspeaker
Table 5: Geometrical form of the distributed in space and time arrays. Value Dimension Point
Scalar module
Line
gradiometrical
Curve
differential module
Plane
gradiometrical module
Scalar array differential differential gradiometrical gradiometrical module gradiometrical differential module
Vector triaxial differential triaxial differential triaxial gradiometrical triaxial
Tensor triaxial vector differential triaxial vector differential triaxial vector gradiometrical triaxial vector
International Scholarly Research Network ISRN Nanotechnology Volume 2012, Article ID 102783, 9 pages doi:10.5402/2012/102783
[4]
Review Article A CNTFET-Based Nanowired Induction Two-Way Transducers Rostyslav Sklyar Verchratskogo st. 15-1, Lviv 79010, Ukraine Correspondence should be addressed to Rostyslav Sklyar, sklyar@tsp.lviv.ua Received 15 December 2011; Accepted 28 February 2012 Academic Editors: C. A. Charitidis and J. Sha Copyright Š 2012 Rostyslav Sklyar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A complex of the induction magnetic field two-way nanotransducers of the different physical values for both the external and implantable interfaces in a wide range of arrays are summarized. Implementation of the nanowires allows reliable transducing of the biosignalsâ&#x20AC;&#x2122; partials and bringing of carbon nanotubes into circuits leading to examination of the superconducting transition. Novel sensors are based on the induction magnetic field principle, which causes their interaction with an ambient EM field. Mathematical description of both the signal and mediums defines space embracing of the relevant interfacing devices. As a result, a wide range of the nano-bio-transducers allow both delivering the variety of ionized biosignals and interface the bioEM signals with further stages of electronic systems. The space coverage and transducing values properties of the state-of-the-art magnetic interfaces are summarized, and directions for their future development are deduced.
1. Introduction: Biophysical Signals, Transducing, and Interface Applications A biosensor is a device that incorporates a biologically active layer as the recognition element and converts the physical parameters of the biological interaction into a measurable analytical signal [1]. Understanding of biosignalsâ&#x20AC;&#x2122; (BS) nature and properties of their mediums are a basis for effective design of magnetic interfaces (MIs). Rapid progress in the advancement of several key science areas including nanoscale interfaces has stimulated the development of electronic sensor technologies applicable to many diverse areas of human activity. For example, the conceptualization and production of electronic nose devices have resulted in the creation of a remarkable new sector of sensor technology resulting from the invention of numerous new types of olfactory-competent electronic sensors and sensor arrays [2]. The growing variety of biosensors can be grouped into two categories: implantable and external. In turn, the last one has two existing paradigms: wearable sensor and noncontact sensor. A wearable sensor had potential to be intrusive, and noncontact sensor methods may still be intrusiveness to a certain extent, while a noncontact sensor is limited in its capability of acquiring physiological signals [3]. Voltage potentials of the living organism and its organs are measured
by both implantable and external electric field probes of high sensitivity [4]. Information on organ activity is obtained by measuring biomagnetic signals. For such purposes a multichannel high-temperature superconducting quantum interference device (high Tc SQUID) system for magnetocardiography (MCG) and magnetoencephalography (MEG) of humans, with high magnetic field resolution, has been developed [5, 6]. The most current sensing devices give us the possibility to receive a full scale of both the internal and external control BS. The internal ones are picking up by polymeric microprobes, CMOS chips, and nanoneedles, while the external by electromyography and neuroprosthetic (electroencephalogram (EEG) and MEG) systems. Improving an informational capability of the interface is implemented by the application of the advanced superconducting transducer and electromagnetic (EM) transistor/memristor [7, 8]. These elements are arranged into the arrays of a different configurations and can cover the order of spaces from macro- to nanolevels. There are a number of methods and devices for transducing different BS into recordable or measurable information. The transfer of nerve impulses (NI) is the main data flow that carries sensory information to the brain and control signals from it and from the spinal cord to the limbs.
2 Moreover, the complex view on BS requires further stages of precise processing in order to decode the received or control information. There are different kinds of transducers/sensors for picking up NI: room-temperature and superconducting, external, and implantable. Development of such devices is increasing the penetration into bioprocess while simultaneously simplifying the exploitation of the measuring systems in order to bring them closer to the wide range of applications. For this reason, the magnetometer with a room-temperature pickup coil (PC) for detecting signals, which can clearly be detected in higher frequency range, was developed in order to simplify the SQUID system. The PC is set outside the cryostat and is connected to the input coil of the SQUID [9] or a channel of superconducting field-effect transistor (SuFET) [10]. On the other hand, implantableinto-nerve fiber transducers are evolving from the ordinary Si-chip microelectronics devices [11] into superconducting and nanodevices [12, 13]. The recent achievements in nanoelectronics can be regarded as a further step in the progress of BS transduction. They give us the possibility to create the most advanced and universal device on the basis of known microsystems. Such a sensor/transducer is suitable for picking up BS— NI, electrically active (ionized) molecules, and the basepair recognition event in DNA sequences—and transforming it into recognizable information in the form of electric voltage, or a concentration of organic or chemical substances. Moreover, this process can be executed in reverse. Substances and/or voltages influence BSs, thereby controling or creating them (BS) [14]. Steady and rapid progress in the robotics field requires ever quicker and better human-machine interaction and the development of a new generation of interfaces for intelligent systems. Such advances give rise to markedly increased biophysical research on the one hand and the need for new bioelectronic devices on the other. Transduction and measurement of BS are key elements of MIs design. There are two means involved in signal transduction: (1) biochemical—by hormones and enzymes; (2) biophysical— by nerve impulses (ionic currents). Let us consider the biophysical ones as useful for the said interfaces design above. There are two values—voltage and electric current—which characterize the pathway of transduction [15]. Calculations of PC arrays were performed with the primary sensor flux transformer sites distributed uniformly on a spherical sensor shell, extending from the vertex to a maximum angle max [16]. The radial magnetometers and gradiometers occupy one site each, there are two orthogonal planar gradiometers at each site and there are three orthogonal magnetometers at each site for vector magnetometers. Coverage can be achieved by designing some kind of density control mechanism, that is, scheduling the sensors to work alternatively to minimize the power wastage due to the overlap of active nodes’ sensing areas. The sensing area of a node is a disk of a given radius (sensing range). The sensing energy consumption is proportional to the area of sensing disks or the power consumption per unit [17]. There are two broad ways of brain-computer interface (BCI): invasive and noninvasive. The invasive technique can capture intracortical action potentials of neurons and thus,
ISRN Nanotechnology provides high signal strength spatiotemporally, for example, prediction of movement trajectory. In noninvasive technique, EEG and MEG have emerged as viable options; both of them have time resolutions in milliseconds. Any activity in brain is accompanied by change in ionic concentrations in neuron leading to polarization and depolarization. Such an electrical activity is measured by EEG, while MEG measures the magnetic field associated with these currents. Electric and magnetic fields are oriented perpendicular to each other [18]. Application of organic-, chemical-, and carbonnanotubes- (CNT-) based FETs for design of the superconducting transducers (SuFETTrs) of BS into different quantities (electrical and biochemical) is the proposed variant of interfacing [19]. The placement of the devices can be carried out both in vivo and in vitro with the possibility of forming the controlling BS from the said quantities. The range of picked up BS varies from 0.6 nA to 10 µA with frequencies from 20 to 2000 Hz. A further step should be the synthesis of the said two methods in order to develop the internal (implantable) nano-bio-interface arrays. This means wrapping of molecular nanowired PC around the axons of a nerve fibre or synapses of neurons in order to obtain the natural biosignals from the nervous system and brain. This leads to sensing access across a vast range of spatial and temporal scales, including the ability to read neural signals from a select subset of single neural cells in vivo. Moreover, this process can be executed in reverse for introducing the artificial control signals with the local neural code into the single cell electrical activity.
2. Biosignals and Nanoelements for Their Transduction As an electrical signal, the biosignal has two components: electrical potential or voltage and ionic or electronic currents. The first component is sufficiently developed and does not require penetration into the substances of biosignal propagation. The marketable progress in transducing of the second component began when the necessary instrumentation for measurement of micro- and nanodimensions had been created [14]. Short platinum nanowires (NWs) already have been used in submicroscopic sensors and other applications. A method of making long (cm) Pt NW of a few nanometers in diameter from electrospinning was described [20]. Those wires could be woven into the first self-supporting webs of pure platinum. Double-gated silicon NW structures (DGSiNW), where the position and/or type of the charge could be tuned within the NW by electric field, have been studied [21]. Self-assembled molecular nanowires were found to be composed of a single crystal, allowing good electrical transport with low resistivity [22]. An interesting structure is that of helical CNT or nanocoils for PCs. Nanocoils offer unique electronic properties that straight CNT do not have. The plasticity of CNT will be relevant to their use in nanoscale devices [23]. Carbon nanocoils (CNCs), as a new type of promising
ISRN Nanotechnology nanomaterials, have attracted considerable attention because of their potential applications, such as parts for nanoor micro-electromechanical systems, EM wave absorbers, reinforced composites, nanosolenoids, and field emission devices [24] Integrated CMOS image sensor device for in vivo neural imaging has been developed. Improvement in the packaging process has resulted in a compact single-chip device for minimally invasive imaging inside the mouse brain [25]. Application of the SuFET’s modifications such as CMOSuFET (low Tc ) [26] and coplanar SuFET (high Tc ) [27] broadens the range of requirements, which are being satisfied by the SuFETTr. Alternatively, an FET-based neurotransducer with CNT or PC kind of input circuit for the nerve and neuron impulse has been designed. A CNTFET with a high-temperature superconducting channel is introduced into the nerve fibre or brain tissue for transducing their signals in both directions [28]. Flexible antennas have the potential to enhance the emerging field of flexible electronics, which is primarily motivated by the desire to incorporate electronics into flexible substrates such as textiles, displays, and bandages [29]. The ability to reversibly deform antennas may also enable new capabilities (e.g., rolling and unrolling for remote deployment, enhanced durability). Relative to conventional copper antennas, fluidic antennas have several advantages [30]. Furthermore, it has been shown that ultrathin layers of metal can display superconductivity, but any limits on the size of superconducting systems remain a mystery. On the other hand, (BETS) 2GaCl4, where BETS is bis (ethylenedithio) tetraselenafulvalene, is an organic superconductor, and in bulk it displays a superconducting gap that increases exponentially with the length of the molecular chain [31]. Graphene-solution-gated FET (G-SGFET) fabricated on copper foil offers outstanding electronic performance, is chemically stable and biologically inert, and can readily be processed on flexible substrates. Not only were the “action potentials” of individual cells detectable above the intrinsic electrical noise of the transistors, but these cellular signals could be recorded with high spatial and temporal resolution. The analysis of the recorded cell signals and the electronic noise of the transistors confirm that graphene transistors surpass state-of-the-art devices for bioelectronic applications [32]. An organic FET (OFET) is characterized by textile process fully compatible size and geometry. This transistor has shown very interesting performances, with typical values of the electronic parameters very similar to those of planar devices. This result is very promising in view of innovative applications in the field of smart textiles [33]. Also FETs with single- and doublewire channels (NWFET) were fabricated to give some indication of the potential application of the molecular wires [22]. Finally, inkjet-printed FETs using carboxyl-functionalized nanotubes as source, drain, and gate electrodes, poly (ethylene glycol) (PEG-) functionalized nanotubes as the channel, and PEG as the gate dielectric were also tested and characterized. Considerable nonlinear transport in conjunction with a high channel current on/off
3
M+
Delivery M+
M+ D
M− G M−
CNT
Vout/in M−
S Diagnostic
Figure 1: Diagnostics of the biomedium with the necessary drugs delivering.
ratio of 70 was observed with PEG-functionalized nanotubes. The positive temperature coefficient of channel resistance shows the nonmetallic behavior of the inkjet-printed films [34]. Finally, FETs with single- and doublewire channels were fabricated to give some indication of the potential application of the molecular wires. Substantial progress has been made in defining the performance limits and exploring applications based on NWFETs [22]. A five-channel FET structure is composed of two double-gate transistors and a bottom single-gate transistor on a silicon-on-insulator. 3D transistor structures such as multiple-gate FETs have been proposed and extensively studied as a promising solution to overcome the scaling limitations of planar bulk devices. They offer excellent multigate control of the channels and higher current drive [35]. In high-performance n-channel OFETs, charge carrier injection at the interface between the organic film and source/drain electrodes plays a crucial role [36].
3. An SuFETTr-Based Devices
Magnetic
Interface
The advent of semiconductor devices with nanoscale dimensions creates the potential to integrate nanoelectronics and optoelectronic devices with a great variety of biological systems. In such a case, 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 measurement problem in one-coordinate-dimensional measurements could be acquired naturally, according to the feedback reaction on the input exposure. Moreover, the organs of the senses of living beings could be regarded in the same way as the natural