Direct-write fabrication of freestanding nanocomposite strain sensors

Abstract

This paper deals with the design and microfabrication of two three-dimensional (3D) freestanding patterned strain sensors made of single-walled carbon nanotube (SWCNT) nanocomposites with the ultraviolet-assisted direct-write (UV-DW) technique. The first sensor consisted of three nanocomposite microfibers suspended between two rectangular epoxy pads. The flexibility of the UV-DW technique enables the sensor and its housing to be manufactured in one monolithic structure. The second sensor was composed of a nanocomposite network consisting of four parallel microsprings, which demonstrates the high capability of the technique when compared to conventional photolithographic technologies. The performances of the sensors were assessed under tension and compression, respectively. The sensors' sensitivities were evaluated by correlating their measured resistivities to the applied displacements/strains. Electrical conductivity measurements revealed that the manufactured sensors are highly sensitive to small mechanical disturbances, especially for lower nanotube loadings when compared to traditional metallic or nanocomposite films. The present manufacturing method offers a new perspective for manufacturing highly sensitive 3D freestanding microstructured sensors.

Nonlinear bending of nanotube-reinforced composite cylindrical panels resting on elastic foundations in thermal environments

“…Note that the geometric nonlinearity in the von Kármán sense is given in terms of e L() in Eqs. (1) and (2). It is worthy to note that the governing Eqs.…”

“…Owing to their remarkable mechanical, electrical and thermal properties, these new nanocomposite materials can be used to make key components in Micro-Electro-Mechanical Systems (MEMS) and Nano-Electro-Mechanical Systems (NEMS) [1,2]. When using carbon nanotubes to replace traditional carbon fibers as the reinforcements in the composites, a small weight percentage of the carbon nanotubes (2-5%) can significantly increase the stiffness and strength of the composites [3][4][5][6].…”

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

“…Current success in 3D printing of fiber composites relies on the fused deposition modeling (FDM) of mechanically weak, thermally unstable thermoplastic fiber reinforced feed stocks3536373839. Recently, a filament-based, ambient temperature 3D printing technique, known as direct-ink writing (DIW) has been utilized to fabricate fiber (i.e., carbon nanotube, ceramic)-epoxy composites4041. DIW is a high-speed and low-cost 3D printing technique that employs a multi-axis motion stage to assemble complex 3D structures by robotically extruding continuous “ink” filaments through the micro-nozzle in a layer-by-layer scheme424344.…”

Nonlinear response of nanotube-reinforced composite cylindrical panels subjected to combined loadings and resting on elastic foundations

“…(1) and (2). It is noted that the governing equations (1)-(4) for a CNTRC cylindrical panel are identical to those of unsymmetric cross-ply laminated cylindrical panels.…”