This paper describes the development of an innovative carbon nanotube-based non-woven composite sensor that can be tailored for strain sensing properties and potentially offers a reliable and cost-effective sensing option for structural health monitoring (SHM). This novel strain sensor is fabricated using a readily scalable process of coating Carbon nanotubes (CNT) onto a nonwoven carrier fabric to form an electrically-isotropic conductive network. Epoxy is then infused into the CNT-modified fabric to form a free-standing nanocomposite strain sensor. By measuring the changes in the electrical properties of the sensing composite the deformation can be measured in real-time. The sensors are repeatable and linear up to 0.4% strain. Highest elastic strain gage factors of 1.9 and 4.0 have been achieved in the longitudinal and transverse direction, respectively. Although the longitudinal gage factor of the newly formed nanocomposite sensor is close to some metallic foil strain gages, the proposed sensing methodology offers spatial coverage, manufacturing customizability, distributed sensing capability as well as transverse sensitivity.
Flexible pressure sensors are of broad interest for applications
including human–machine interfaces, wearable electronics, and
object/motion detection. However, complexities associated with constituent
materials, fabrication processes, sensing mechanisms, and hardwiring
often hinder the large-scale applications of using high performance
pressure sensors reported in the literature. Here we demonstrate a
large-area, highly flexible, conformable, and mechanically robust
pressure sensor using a silicone elastomer with an embedded nonwoven
textile carrier coated with carbon nanotubes. The selected silicone
polymer allows through-thickness deformability of the sensor while
the high modulus textile carrier ensures in-plane stiffness and stability.
The sensor has an initial electrical conductivity of 4.4 ± 0.38
S/m and is fabricated using a straightforward dip coating and polymer
infusion process and can be easily scaled-up for large-scale applications.
On the basis of its hierarchical composite structure, this piezoresistive
pressure sensor possesses extremely high resilience under compression,
a repeatable monotonic positive pressure correlation, and an ultrawide
elastic working range (5.5 ± 0.5 MPa) that can be segmentally
linearized. A true two-dimensional modality for spatial pressure mapping
is realized by utilizing electrical impedance tomography (EIT) and
demonstrated to yield conductivity maps that can estimate the location,
shape, and amplitude of both localized and distributed pressure with
simple contact areas.
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