Thermally Drawn CNT-Based Hybrid Nanocomposite Fiber for Electrochemical Sensing

Abstract

Nowadays, bioelectronic devices are evolving from rigid to flexible materials and substrates, among which thermally-drawn-fiber-based bioelectronics represent promising technologies thanks to their inherent flexibility and seamless integration of multi-functionalities. However, electrochemical sensing within fibers remains a poorly explored area, as it imposes new demands for material properties—both the electrochemical sensitivity and the thermomechanical compatibility with the fiber drawing process. Here, we designed and fabricated microelectrode fibers made of carbon nanotube (CNT)-based hybrid nanocomposites and further evaluated their detailed electrochemical sensing performances. Carbon-black-impregnated polyethylene (CB-CPE) was chosen as the base material, into which CNT was loaded homogeneously in a concentration range of 3.8 to 10 wt%. First, electrical impedance characterization of CNT nanocomposites showed a remarkable decrease of the resistance with the increase in CNT loading ratio, suggesting that CNTs notably increased the effective electrical current pathways inside the composites. In addition, the proof-of-principle performance of fiber-based microelectrodes was characterized for the detection of ferrocenemethanol (FcMeOH) and dopamine (DA), exhibiting an ultra-high sensitivity. Additionally, we further examined the long-term stability of such composite-based electrode in exposure to the aqueous environment, mimicking the in vivo or in vitro settings. Later, we functionalized the surface of the microelectrode fiber with ion-sensitive membranes (ISM) for the selective sensing of Na+ ions. The miniature fiber-based electrochemical sensor developed here holds great potential for standalone point-of-care sensing applications. In the future, taking full advantage of the thermal drawing process, the electrical, optical, chemical, and electrochemical modalities can be all integrated together within a thin strand of fiber. This single fiber can be useful for fundamental multi-mechanistic studies for biological applications and the weaved fibers can be further applied for daily health monitoring as functional textiles.

The Development of Aptamer-Coupled Microelectrode Fiber Sensors (apta-μFS) for Highly Selective Neurochemical Sensing

“…We then calculated the linear sensitivity across different devices ( N = 6), which had a median of 40.9 pA/μM and an interquartile range of 21.8 to 66.4 pA/μM (Figure h). The main reason for this variance in sensitivities stems from the differences in the exposed CNTs at the fiber surface to the host aptamers.…”

“…Leveraging the thermal drawing process, we fabricated various microelectrode fibers with an electrode in the center surrounded by organic solvent resistive polymer claddings such as polyethylene (PE) or poly­(ether imide) (PEI) (Figure a and Supporting Information (SI) Figure 1). The central carbon-electrodes were based on the 10 wt % CNT composites that we have developed in previous studies . In comparison to that in previous studies, − the surface of the CFE needs to be electrochemically activated to form functional groups to couple aptamers.…”

“…Though our group was the first to develop a fiber-type biochemical sensing device for pH monitoring in the hippocampus, , an extrinsic functional component, a miniaturized field-effect sensor chip, was introduced to the fiber. And recently, a carbon-based polymer electrode with functional nanomaterials such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs) , has been successfully integrated within such fibers. Compared with conventional CFE-microelectrodes, such CNT or CNF based carbon-electrode fibers have high electrochemical performance, which can be easily produced with a high yield.…”

Polymeric Scaffolds for Regeneration of Central/Peripheral Nerves and Soft Connective Tissues

“…[ 78 ] Very recently, Nishimoto et al designed and fabricated microelectrode fibers made of carbon nanotube (CNT)‐based hybrid nanocomposites using fiber drawing for ferrocene methanol (FcMeOH) and dopamine (DA) detection, as well as selective sensing of Na + . [ 79 ] The aforementioned studies have shown promising potentials of fiber‐drawn scaffolds and biohybrids for tissue regenerations and other biomedical applications (e.g., biosensing).…”

Microelectronic fibers for multiplexed sweat sensing

“…The fiber consists of two polymer electrodes based on carbon-based polyethylene (CPE) electrodes and stainless-steel wires directly beneath them, an internal microfluidic channel between the electrodes, and an outermost polycarbonate (PC) cladding. Previously, thermally drawn fiber-based electrochemical probes used fiber tips as sensing surfaces, which suffered from shortcomings such as small terminal sensing area, limited scalability, weak signal, and low sensitivity [ 20 – 22 ]. In this study, we used laser machining techniques to expose the CPE within the PC cladding at designated locations along the longitudinal sides of the fiber, which produced a large sensing surface.…”