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applications. The Models for Simulation Based Selection of 3D Multilayered Graphene Biosensors E. Lacatus *1, G.C. Alecu1, and A. Tudor1 1Polytechnic University of Bucharest * E. Lacatus: elena.lacatus@upb.ro Abstract: At the forefront of a new generation of sensors grapheme and grapheme composite materials are intensively studied for medical and biosensing outstanding electrical, mechanical and quantum properties of grapheme make them a promising material solution to overlap the existing gap between biological and non-biological systems into a continuum like-viscoelastic integrated model. Through COMSOL Multiphysics ® modeling and simulation were fitted solutions for a multilayered biosensing device structure from the presently known graphene (G), graphene- oxide (GO) and composite materials including different forms of graphene ( graphene nanoribbons –GNRs, reactive graphene oxide –RGO, and TWEEN paper –TwGP). Keywords: graphene, biosensor, Fröhlich quantum non-linear thermodynamics 1. Introduction Figure 2. Basic and functionalized graphene structures (ChemBio 3D Ultra©) coherence, identified the best phonon, a b Figure 1. (a) Graphene model; (b) Functionalized bilayer-graphene structure (ChemBio 3D Ultra©) Intensely studied in the last decade, graphene (G), graphene oxides (GO), reactive graphene oxides (RGO), graphene nanoribbons (GNRs) and many other graphene based composite materials are continuously approach the medical and biosensing area with the aim of defining new material solutions for properly personalized medical and therapeutic solutions. applications to With large similarities to the surface of graphite (Figure 1), graphene (G) can adsorb and desorb different type of atoms and molecules, remaining highly conductive [1]. This property can be used for sensor applications. It is largely known that single- layer graphene (1G) is much more reactive than 2G, 3G (<10 layers) graphene multilayer structures [2,3]. However, the edge of the graphene is more reactive than the surface, graphene being a fairly inert material, and thus an ideal candidate for bio-sensors. ; a b Figure 3. MATLAB© models of electronic properties of graphene :(a) 20 atoms – armchair structure; (b) 20 atoms – zig-zag structure Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
The aim of the modeling and simulation of the multilayered graphene structures is mainly focused on the device response at different types of energy stimulus reaching the active surfaces of the 3D bio-sensing structures under the main restrictions of biocompatibility and non-toxicity (Figure 2, Figure 3). 2. Models Definition The most accessible and nonintrusive interface of a sensor with humans is on the skin surface. Not only because skin is the organ that has the widest area of the human body, but because it has differentiated responses to internal and external stimuli, thus being an accessible environment for physical and chemical data gathering.Based on FET (Field Effect Transistor) properties [15,17] that can relate human skin to the of G/GO/TwGP [1,4,5,13,16,18] two biosensing devices were designed (Figure 4 c, d). characteristics presently known Figure 4 Multilayer graphene sensing concepts: (a),(b) General GNRs multilayer concept [4,18] (c) single layer G/GO sensor; (d) multilayer G/GO/TwGP sensor – structure graphene For these studies were considered the main interfaces between: human skin – hydrogel (PVA Hydrogel); PVA polymer Hydrogel based module (G/GO/TwGP); graphene module – electrodes (Ag); graphene/electrodes – substrate (Silica glass SiO2) (Figure 4 c, d).For each of these to interfaces were describe process microvariables as well as the environmental stimuli influences (macrovariables) as follows: identified models able evolution the the of • Two electrodes biosensing module (Figure 4c) including skin, PVA Hydrogel, graphene (G) and graphene-oxide (GO) functionalized with different proteins (Alpha Helix, Loricin and Lysozyme) • Four electrodes module (Figure 4 d) that considers the same main interfaces with both graphene composite structure and without it, for the same environmental stimuli, in order to objectively graphene responses (Figure 5,…15) differentiate the All these models are having the same continuum-like background of a biosensor device structure based on weak van der Waals interaction forces that describe the nonlinear into a surrounding behavior of graphene viscoelastic environment classical Kirchhoff plate theory [14] through In the Equation 1, used for modeling single layer graphene vibration response based on Kirchhoff plate theory [14] α1 and α3 represents the linear and nonlinear interaction forces: (1) where: Nx, Ny are biaxial in-plane loads; a, b- length, width of the single layer graphene; h- thickness of the single layer graphene; p – distributed transverse load per unit area (due to surrounding medium effect) ; D is the bending stiffness of the plate: E is the Young’s modulus; ν – Poisson’s (2) ratio; ρ – mass density; - Laplace operator: (3) is properly described The density of charge, characterizing all through interfaces, nonlinear thermodynamics with electron – phonon (ē – ph) , phonon – phonon (ph – ph) and ion –phonon interactions. Thus for all models were studied the charge density distributions of electric, thermal and acoustic field stimuli responsible for (ē – ph), (ph – ph) and (ion –ph) interactions (Figures 5,…, 15). Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
Figure 5. Substrate (SiO2) stress distribution (a) 2 electrodes device; (b) 4 electrodes device b a Figure 6. Electric potential on interface: (a) 2 electrodes device; (b) 4 electrodes device Figure 7. Temperature distribution at interface (isosurfaces) (a) 2 electrodes device; (b) 4 electrodes device 3. Use of COMSOL Multiphysics add-on MATLAB© model and For the envisaged multilayer structures of graphene biosensing devices a graphene model was firstly created in ChemBio 3D Ultra©. Its characteristics have been exported to MATLAB© and thus different process parameters and material properties were consistently interlinked for further analyses and simulations (Figure 2,3). the associated properties were exported through the LiveLinkTM for MATLAB© in COMSOL Multiphysics ® and thus the variability of the structure properties (Figure 3) could be properly analyzed in at the device scale (Figure 5,…,15). The models designed to include environmental stimuli acting upon human body were focused either on the thermal slight modifications or electric conductance variations due to emotional rose or on area exposure to acoustic waves (Figure 6,7). Acoustic Module of COMSOL Multiphysics ® and Equation Based Models were used to define interface response to variations of environment acoustic pressure (frequency vary from 1000 Hz to 8000 Hz) 4. Results A large number of device module types have been tested in order to define the best response of the hydrogel- polymer layer (PVA Hydrogel) on the graphene sheets and of the protein functionalized graphene biosensors. a b Figure 8. von Misses stress shell: (a) 2 electrodes device; (b) 4 electrodes device Figure 9. Temperature distribution : (a) 2 electrodes device; (b) 4 electrodes device Figure 10Acoustic stimuli over graphene sensing structure(4 electrodes device): (a) f=1500Hz; (b) f=7000 Hz Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
For each of these modules the biologic responses and the field excitations have to reach simultaneity under the COMSOL Multiphysics ® model (Figure 4). a Figure 11 Pressure distribution (skin-polymer)/sensor interface: (a) 2 electrodes device; (b) 4 electrodes device Figure 12 Spatial distribution of flux energy on graphene bisensor (4 electrodes device) . Figure 13 Interfaces charge distributions (4 electrodes device) Figure 14 Membrane stress under environmental stimuli: 2 electrodes device Figure 15 Interface stress under environmental stimuli: (a) 2 electrodes device; (b) 4 electrodes device 5. Discussion The analyzed biosensing device models, regardless their design solution (two or four electrodes; single- or multilayer graphene; graphene composite material) revealed through simulations output data the “sensing” ability of the graphene –based concept model. For each module type the graphene/ graphene composite materials generate clearly differentiate the environmental stimuli, or responses process microvariables thus confirming the biosensing ability of this class of materials. evolution, to Operating with a continuum model for all interfaces (ē – ph, ph – ph and ion –ph) and harvesting biological charge density variations to relate them to environment stimuli, the 3D multilayered graphene biosensors models and simulations offered valuable design solutions 6. Conclusions Making the best use of the flexible modules of COMSOL Multiphysics ® the most relevant device properties of the multilayered graphene biocompatible structures could be determined and, mostly important, could be related to the complex interface phenomena at human skin level. Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
7. References 1. J.-C Charlier, et al., Electron and Phonon Properties of Graphene: Their Relationshop with Carbon Nanotubes , Carbon Nanotubes, Springer-Verlag, Berlin, http://dx.doi.org/10.1007/978-3-540-72865- 8_21, (2008) 2. H. Fröhlich , F. Kremer, Coherent Excitations in Biological Systems , Springer- Verlag, ISBN 978-3-642-69186-7,(1983) 3. H.Fröhlich, Biological Coherence and Response to External Stimuli , Springer, ISBN 978-3-642-73309-3, (1988) 4. A.K. Geim, K.S. Novoselov , The rise of graphene. Nat. Mater. 6, 183, (2007) 5. O. Heinonen, P.L. Taylor, A Quantum Approach to Condensed Matter Physics; Cambridge University Press: Cambridge, UK, 2002. 6. B. Hille, Ion Channels of Excitable Membranes, Sinauer, (2001) 7. E. Lacatus, Engineering Self-Assembly through Modeling Nanostructures, EngOpt 2010, The 2nd International Conference on Engineering Optimization, 6-9 September 2010, Lisbon, Portugal, ISBN 978-989- 96264-3-0, (2010) ASME 8. E. Lacatus, F.A. Savulescu, Nano-Bio-Cogno Model of Acoustic Patterning for Molecular Neurostimulation, Proceedings DOI:10.1115/FMD2013-16178, (2013) 9. E. Lacatus, Ion Channel Path of Cellular Transduction, Biochimica et Biophysica Acta (BBA), Bioenergetics Volume 1837, p.110- 111, DOI: 10.1016/j.bbabio.2014.05.266, (2014) 10. E. Lacatus, et al., Analysis of 3D Biocompatible Additive Structure Using COMSOL Software, COMSOL Conference , Cambridge , (2014) Multiphysics® 11. E. Lacatus, et al., From Music to Non- COMSOL COMSOL Invasive Multiphysics® Conference, Cambridge, (2014) Therapies Models, via 12. E. Lacatus, Modeling a Multilayered Graphene 6th International conference on Advanced Nano Materials, Aveiro, (2015) Biosensing Structure, 13. D.L. Mafra, P.T. Araujo, Intra- and Interlayer Electron-Phonon Interactions in BiLayer Graphene, Appl. Sci. 2014, 4, 207- 239; doi:10.3390/app4020207, (2014) 14. M.H. Mahdavi et al., Nonlinear vibration and postbuckling analysis of a single layer graphene sheet embedded in a polymer matrix, Physica E 44 1708–1715, (2012) 15. M.V. Mesquita et al., Systems Biology: An Information-Theoretic-Based Thermo- Statistical Approach, Brazilian Journal of Physics, vol. 34, no. 2A, June, (2004) 16. A.H.C. Neto et al., The electronic properties of graphene. Rev. Mod. Phys. 81, 109–162, (2009) 17. P.V. Tsaklis, Presentation of acoustic waves’ propagation and their effects through human body tissues, Human Movement, 58, vol. 11 (1), 58–65, DOI: 10.2478/v10038- 009- 0025-z, (2010) 18. D. Verma et al., Vibration mode localization single- and multi-layered graphene Computational Materials in Nanoribbons, Science 95,41–52, (2014) 8. Appendix MODEL LIBRARY: Device SLGS (G/GO) E.g.: Material 1 -Silica Glass Model Parameters Details Input voltage, Layer thickness, Electric conductivity of silver, Electric conductivity of Nichrome, Air temperature Heat transfer film coefficient, Air Fluid temperature, Heat transfer film coefficient, fluid Silica Glass Coefficient expansion Heat capacity /constant pressure Density, Thermal conductivity Young's modulus ,Poisson's ratio thermal of Definitions Material 1 Material 1 Parameters Equations Material 1 Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
Equations Material 4 Mesh Frequency domain Solver configuratio n Plot groups Normal; Number of degrees of freedom solved for: 2761 (plus 210 internal DOFs). Frequencies: range(1000,500,8000) COMSOL Multiphysics AC/DC Module Heat Transfer Module Structural Mechanics Module Acoustic module Stress (Solid), Temperature (ht); Isothermal Contours (ht), Electric Potential (ecs); Stress (shell); non- deformed Geometry (shell); surface losses (freq.1000-8000Hz); Interface stress 01(freq.1000-8000Hz); Interface stress 02(freq.1000-8000Hz); Displacement (freq.1000-8000Hz); Temperature (due vibration); Mesh contour; Acoustic pressure 01; Acoustic pressure 02; Acoustic pressure 03; For each material and interface layer of the biosensing devices were generated similar reports with and without acoustic stimulation. Mesh Solver configuration Plot groups Normal; Number of degrees of freedom solved for: 2761 (plus 210 internal DOFs). COMSOL Multiphysics AC/DC Module CAD Import Module Heat Transfer Module Structural Mechanics Module Stress (Solid), Isosuface : Total stored energy For each material and interface layer of both devices were generated similar reports. MODEL LIBRARY: Acoustic stimulation of devices MLGS (G/GO/TwGP) Model Parameters Details Definitions Used modules Material 1 Material 2 Material 3 Material 4 Material 1 Parameters Equations Material 1 Equations Material 2 Equations Material 3 Input voltage, Layer thickness, Electric conductivity of silver, Electric conductivity of Nichrome, Air temperature Heat transfer film coefficient, Air Fluid temperature, Heat transfer film coefficient, fluid COMSOL Multiphysics AC/DC Module CAD Import Module Heat Transfer Module Structural Mechanics Module Substrate (Si) Silica Glass Electrodes TWEEN/RGO (TwGP) Coefficient of thermal expansion; Heat capacity /constant pressure Density Thermal conductivity Young’s modulus Poisson’s ratio Excerpt from the Proceedings of the 2015 COMSOL Conference in Grenoble
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