Potential of HCCNTs for nano-mechanical mass sensor applications Zoran P. Popović, Saša Dmitrović, Milan Damnjanović and Ivanka Milošević NanoLab, QTP Center, Department of Physics, University of Belgrade, Studentski trg 12, 11158 Belgrade, Serbia Introduction We explore potential of helically coiled carbon nanotubes (HCCNTs) for applications as nano-mechanical resonators in mass and strain sensors. Using symmetry-based atomistic modeling, we consider both bridged and cantilevered configurations and also calculate fundamental frequencies of homogenously deformed HCCNTs taking into account impact of the strain-induced deformations. Finally, we make comparative analysis of the performances of HCCNT-based and SWCNT-based nano-mechanical resonators.. Abstract Predicted in the early nineties: Itoh et al., PRB 48 Observed experimentally in 1994: S. Amelinckx et al., Science 265; X. B. Zhang et al. , Europhysics Lett. 27 Selective production by catalytic CVD: D. Fejes, L. Forro and K. Hernadi, Phys. Status Solidi B 247 (2010) SEM Images of Carbon Microcoils S. Motojima et al., Materials Lett. 61 (2007) TEM Image - Coil with a Regular Pitch Pitch = 50 nm Max length = 10 µm K.Hernadi, L. Thien-Nga, L. Forro, J. Phys. Chem. B (2001) Potential applications: Sensors NanoVelcro . Structural Model of Helically Coiled CNTs Mechanical Properties of HCCNTs (a) Symmetry generating elements and geometrical parameters of HCCNTs; (b) Cohesive energies of the corrugated [1] and un-corrugated models [2] of HCCNTs (upper panel) and relative difference of their tubular radii (lower panel) as a function of the graph parameter n7 ; (c) LR [3] triple connected graph (1,((3,0),(0,3))) of pentagons (black), hexagons (white) and heptagons (dark grey) and rectangle denotes the unit-cell of super-cell ((3,0),(0,3)); augmented graph (1,2,2,2,((3,0),(0,2))): inserted are nr=2 rows of hexagons (between initial unit cells), n5=2 columns of hexagons (between pairs of pentagons) and n7=2 columns of hexagons (between pairs of heptagons); rectangle denotes the unit-cell of super-cell ((3,0),(0,2)), [2]. Young’s modulus along the coil axis Transversal compressive Young’s modulus Yt  [0.15, 0.35] TPa, in agreement with the measurements by Volodin et al., Nano Letters 4 (2004) Extreme elasticity [1] Z. P. Popović et al., Carbon 77 (2014) [2] I. Milošević et al., pss (b) 249 (2012) [3] I. László and A. Rassat, J. Chem. Inf. Comput. Sci. 43 (2003) Range of diameters , coil pitches & length data Characteristic data Modeled As-synthesized Helix diameter D 1.2 nm–44.0 nm 30.0 nm – 88.0 nm Coil pitch p 0.9 nm–46.8 nm 31.0 nm – 53.2 nm Tube diameter d 0.4 nm–3.4 nm 9.6 nm – 29.9 nm Tube length L Infinite 150 nm – 700 nm Inclination angle χ 5◦ – 64◦ --- Monomer length a 0.8 nm–10.8 nm --- D/d 0.9–31 3.3 – 6.8 [4] D. Fejes et al., ECS Solid State Letters 2 (2013) Axial deformation causes significant changes of the helical radius and bond angle distribution, while at the same time tubular parameters and bond lengths are only slightly changed. Spring constants (per helical pitch of a HCCNT) k  [0.26, 9.70] N/m Helically Coiled CNTs as Nanomechanical Mass Sensors Fundamental frequency vs. HCCNT geometrical parameters Fundamental frequency vs. attached mass Sensitivity: HCCNTs vs. SWCNTs Responsivity functions Fundamental frequency of statically compressed tubes Strain sensing http://qtpcenter.ff.bg.ac.rs