Textile sensors platform for the selective and simultaneous detection of chloride ion and pH in sweat

Abstract

The development of wearable sensors, in particular fully-textile ones, is one of the most interesting open challenges in bioelectronics. Several and significant steps forward have been taken in the last decade in order to achieve a compact, lightweight, cost-effective, and easy to wear platform for healthcare and sport activities real-time monitoring. We have developed a fully textile, multi-thread biosensing platform that can detect different bioanalytes simultaneously without interference, and, as an example, we propose it for testing chloride ions (Cl−) concentration and pH level. The textile sensors are simple threads, based on natural and synthetic fibers, coated with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) and properly functionalized with either a nano-composite material or a chemical sensitive dye to obtain Cl− and pH selective sensing functionality, respectively. The single-thread sensors show excellent sensitivity, reproducibility, selectivity, long term stability and the ability to work with small volumes of solution. The performance of the developed textile devices is demonstrated both in buffer solution and in artificial human perspiration to perform on-demand and point-of-care epidermal fluids analysis. The possibility to easily knit or sew the thread sensors into fabrics opens up a new vision for a textile wearable multi-sensing platform achievable in the near future.

Textile Chemical Sensors Based on Conductive Polymers for the Analysis of Sweat

“…The textile pH sensor showed a normalized sensitivity of (7.5 ± 0.3) × 10 −3 pH −1 in the range 2–7, with no penalization of the sensing performance if compared to the rigid analogous fabricated on a glass substrate. The same functionalization strategy based on PEDOT:PSS/PEDOT:BTB was also adopted to design a thread pH sensor [ 83 ]. The textile sensor was capable of detecting pH selectively during simultaneous recordings in combination with another thread-based sensor for Cl − detection and will be discussed in the section entitled “Multi-sensing platforms”.…”

“…Recently, Possanzini et al [ 83 ] reported a fast, cost-effective and innovative strategy to fabricate a textile multi-sensor platform that merged a versatile and referenceless geometry structure with the robustness of a potentiometric-like transduction mechanism. The multi-thread sensing platform sketched in Figure 7 B i could stably measure pH ( Figure 7 B ii) and Cl − concentration ( Figure 7 B iii) simultaneously and selectively.…”

“…Illustration of the textile multi-thread sensor platform. Current vs. time plot for cotton-based (ii) chloride and (iii) pH sensor in universal buffer solution [ 83 ]. ( C ) i.…”

Metallisation of Textiles and Protection of Conductive Layers: An Overview of Application Techniques

“…Since textiles usually act as natural insulators, it is necessary for them to become conductive prior to electrodeposition. This is feasible by the creation of conductive layers (in a pre-treatment step) on a textile surface, using different metals, such as Ag [51,87], Cu, [88][89][90], Ni [91], Mxenes [92], Ni-Co selenide nanowires [93], NiMoO 4 /CoMoO 4 nanorods [94], LaMnO 3 /MnO nanoarrays, ZnO nanostructures deposited on an Ni-Cu-Ni conductive layer [95], and LiMn 2 O 4 [96], conductive polymers [97] or carbon-based materials [11,[22][23][24][25][26]. Schematic presentation of a typical electrochemical deposition process of a metallic layer onto PES fabric, using a three-electrode system, is shown in Figure 5a, where the deposition of Ni 3 Se 2 NPs is carried out on the conductive fabric (used as a working electrode), resulting in a metallic polyester layered fabric.…”

“…[ 98 ] Copyright 2021, John Wiley and Sons); ( b ) average resistance values of differently electroplated conductive threads (reprinted with permission from Ref. [ 97 ] Copyright 2021, Springer Nature Limited); ( c ) working principle of the thread sensor that detects chloride ions, pH and sweat simultaneously (reprinted with permission from Ref. [ 97 ] Copyright 2021, Springer Nature Limited); ( d ) SEM image of PET coated uniformly with amorphous NiWO 4 (adapted from Ref.…”