Construction of a Two-Dimensional Response Network in Three-Dimensional Composites to Dramatically Enhance Sensor Sensitivity: A Simple, Feasible, and Green Regulating Strategy

Abstract

A simple, feasible, and environmentally friendly method for supercritical fluid-assisted construction of a two-dimensional (2D) response network in three-dimensional (3D) composites is proposed to improve sensor performance so as to meet the requirement of new-generation strain sensors including high sensitivity, large strain range, and other auxiliary properties, such as light weight and thermal insulation. The mechanism is that cell wall stretching in the supercritical fluid foaming process changes the conductive fiber dispersive status by eliminating agglomeration and facilitating orientation in 3D cells. For the thermoplastic polyurethane (TPU)/carbon nanofiber (CNF) foam strain sensors manufactured in this work, there is an optimal cellular structure, that is, an optimal 2D response network in 3D composites to maximize sensitivity, and the gauge factor (GF) of the foamed TPU/CNF strain sensor is increased by 89 times compared to that of the unfoamed composite, together with increased thermal insulation and lightweight performance than the unfoamed composite. The obtained TPU/CNF foam strain sensor shows good stability and repeatability in human motion detection. To enlighten the structural design, a 2D response network model in a 3D foam for a foam strain sensor is established for the first time. The model reveals that filler content and aspect ratio are the key points to regulate the response network and there is an optimal value for these two factors to maximize the sensitivity in a foam strain sensor. Therefore, the knowledge on foam strain sensors based on the experimental and theoretical results in this work provides a new structural design strategy for sensing materials and guides the optimization of the sensing structure to improve sensor sensitivity.

Two-dimensional MXene nanosheets on nano-scale fibrils in hierarchical porous structure to achieve ultra-high sensitivity

“…In such a process, the electrically insulated polymeric three-dimensional (3D) structure is immersed in a solution dissolved or suspended with electrically conductive components which assemble in the polymeric structure to prepare the piezoresistive sensor. 30 Such electrically conductive components are commonly carbonaceous materials, such as carbon nanotubes (CNT), 33,34 reduced graphene oxide (rGO) 35,36 or carbides and nitrides of transition metals like MXene. 37 Comparing with the one-dimension (1D) nanomaterial, the two-dimension (2D) nanomaterial is more enriched with contacts attributed from its abundant stacking status.…”

Sustainable polyester vitrimer capable of fast self-healing and multiple shape-programming via efficient synthesis and configuration processing

“…34,35 Therefore, the molecular chains disorientate, and the foam materials shrink before selfhealing when the molecular chain segments are available to move. 9,36 Alternatively, despite the prominent sustainability of foams, it is difficult to obtain vitrimer foam given that the strong melt strength restricts cell growth. 37 Therefore, it will be a milestone to realize the repairability of polymeric foam and determine the foaming behavior of vitrimers to further enhance the sustainability of polymers.…”

Optimization of Electrical, Dielectric, and Electromagnetic Response in Nanocomposite Foam by Balancing Carbon Nanotube Restricted Orientation and Selective Distribution

“…Dielectric and conductive nanocomposites have many advantages, such as light weight, − easy processing, corrosion resistance, and easy structure–electrical regulation . Hence, they have great potential to be used as metal anticorrosive coating, , capacitor energy storage material, − wave-absorbing material, − electronic sensors, , lithium ion batteries, , and so on. When adding conductive particles into a polymer matrix, the obtained nanocomposite become dielectric material and then become conductive material as the filler concentration increases .…”