Electromechanical Sensors Based on Carbon Nanotube Networks and Their Polymer Composites

Abstract

Abstract.A network of entangled multiwall carbon nanotubes and the composite consisting of filter-supported multiwall carbon nanotube network are conductors whose conductivity is sensitive to compressive stress both in the course of monotonic stress growth and when loading/unloading cycles are imposed. The testing has shown as much as 100% network conductivity increase at the maximum applied stress. The entangled carbon nanotube networks are prepared by vacuum filtration method and peeled off from the filter. The carbon nanotubes are used in pristine condition or chemically functionalized. The filtersupported entangled networks are prepared by the nanotube dispersion filtration through a non-woven flexible polystyrene filter. The nanotubes infiltrate partly into the filter surface pores and link the accumulated filtrate layer with the filtering mat. The filter-support increases nanotube network mechanical integrity, the composite tensile ultimate strength and affects favorably the composite electrical resistance. Other obvious effect of the supporting polymer is reduction of the resistance temperature dependence. Moreover, the conductivity of carbon nanotube networks manifests also organic vapor dependence. The dependence is reversible, reproducible, selective as well as influenced by nanotube oxidation.

The sensing properties of carbon nanotube filled copolymers for VOC vapors detection

“…According to its molecular structure, acetone is of slightly less polar character than ethanol and is expected to permeate the copolymer matrix slowly, which results in the observed relatively small sensitivity among tested compounds. Toluene has a moderate influence on the resistance change, which is in accordance with its ability to dissolve both the styrene and isoprene blocks of the copolymer and moderate permeability through the copolymer [8]. The highest sensitivity of the sensor was observed for heptane.…”

A Flexible Multifunctional Sensor Based on Carbon Nanotube/Polyurethane Composite

“…Similar concepts for such composite structures are used as novel types of sensors [4] or as an active part of sensing composites [5,6].…”

Deformation theory of an electro-conductive composite composed of entangled network of carbon nanotubes embedded in elastic polyurethane

“…The practical use of carbon nanotube (CNT) structures demonstrates their application in the field of sensing technology as novel types of sensors [1]. The interconnected CNT structures are capable of detecting macroscopic electrical resistance change induced by their deformation.…”

“…The CNT based strain sensitive elements usually consist of a pure CNT entangled network of buckypaper when the resistance response to deformation is governed by nanotube interactions [1,[3][4][5][6][7][8]. The decisive role is played by local resistance in nanotube contacts and the straightening and buckling of nanotubes what affects the number of contacts between nanotubes [5].…”

“…The decisive role is played by local resistance in nanotube contacts and the straightening and buckling of nanotubes what affects the number of contacts between nanotubes [5]. Both the tensile [3,5], and compressive [1,6,7] deformation of CNT entangled network was tested. In the case of tensile load, CNT network is attached to the surface of monitored tensile specimen by epoxy resin [8], or is encapsulated into the specimen [5].…”