Fabrication and characterization of a flexible capacitive sensor on PET fabric

Abstract

Purpose There is a developing interest in flexible sensors, especially in the new and intelligent generation of textiles. The purpose of this paper is to fabricate a flexible capacitive sensor on a PET fabric and to investigate some affecting factor on its performance. Design/methodology/approach PET fabric, coated with graphite or with graphite/PEDOT:PSS, was applied as electrodes. Two types of electrospun nanoweb layers from polyamide and polyvinyl alcohol polymers were used as dielectrics. Some factors including electrode area, fabric conductivity, fabric roughness, dielectric thickness, dielectric insulation type and vertical pressure were considered as independent variables. The capacity of the sensor and its detection threshold considered as the outcome (response) variables. Control samples were fabricated by using aluminum plates and cellulosic layer as electrodes and dielectric, respectively. Findings Results showed that post-coating with PEDOT:PSS would improve the conductivity of electrodes up to 300 Ω in comparison with just graphite-coated samples. It was also found that either by improving the conductivity or increasing the area of electrode plates the sensitivity of sample would be increased in pressure stimulating tests. Originality/value The fabric sensor showed remarkable response toward pressure with a lower detection threshold of 30mN/cm2 (obtained capacity ~ 4×104 pF) in comparison with aluminum electrode sensors.

Recent Progress of Wearable Piezoelectric Nanogenerators

“…The number of known conductive polymers is enormous. Important examples include: poly­(3,4-ethylenedioxythiophene) (PEDOT), poly­(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), polypyrrole (PPy), polyaniline (PANI), and polyacetylene (PA) . Among the many conductive polymers, PPy was used in wearable devices as electrode material because of its environmental stability and compatibility with living tissue. , However, major problems that still limit the application of PPy include the poor adhesion between PVDF and PPy.…”

Flexible Sensors—From Materials to Applications

“…PEDOT:PSS films have a stable conductivity (0.26 S/cm) that can be tuned by chemical modification dependent on the nature and degree of doping, achieving a conductivity of 30 S/cm with a baseline resistance 38 Ω/m [139,143]. Flexible sensors can be fabricated using PEDOT:PSS by electrodeposition [143,144], aqueous dispersion [139], mixing [139], inkjet printing ( Figure 4c) [145], spraying [146], chemical oxidation [147], vapor deposition polymerisation (VDP) [147,148], and can be patterned via photo lithography [149]. PEDOT:PSS exhibits excellent electric transport properties for large surface areas and promotes a higher electrocatalytic activity making this material ideal for the fabrication of solar cells [144,150,151].…”

“…Further enhancements on the carrier transport can be achieved by an increase on the surface area with the fabrication of nanostructures, such as nanotubes (conductivity of 61 S/cm) or nanocables (conductivity of 71 S/cm) [147]. Mixtures of graphene and PEDOT:PSS have also been sprayed on PET yarns, achieving a surface resistance of 300 Ohms and a capacitance of 541 pF reaching up to 375 pF/cm 2 [146]. Non-conventional geometries were employed to build a wrinkled energy harvester and sensor [122], which was achieved by depositing PEDOT:PSS on a stretched polydimethysiloxane (PDMS) substrate (distance of ≈5 µm, thickness of ≈ 0.74 µm).…”

“…The various approaches in fabricating pressure sensors include resistive types [7,21,39,70,95,104,127,136,208,296,[413][414][415][416][417][418][419][420][421][422][423], capacitive types [25,71,146,303,310,321,352,[424][425][426][427], field-effect transistors [9][10][11]193,428], and the piezocapacitive and piezoelectric properties of materials [214,[429][430][431]. Pressure sensors' most important parameters are sensitivity, detection range and response time.…”

E-Skin: The Dawn of a New Era of On-Body Monitoring Systems

“…PET layers are frequently used as substrates for different conductive materials such as nanofibers [57], thin indium-tin-oxide (ITO) [58], graphite or with graphite/PEDOT:PSS [59], but it can suffer significant damage when highly bent [60].…”