Sensor Manufacturing Research Articles

Incorporation of ZnO encapsulated MoS2 to fabricate flexible piezoelectric nanogenerator and sensor

Polymer based piezoelectric composite has attracted much attention in recent years due to its applicability in the manufacture of piezoelectric nanogenerators and sensors, high piezoelectric performance, high flexibility and easily shaping properties. In this work, ZnO with good piezoelectric properties was grown on the exfoliated MoS2 nanosheets by employing in situ polymerization, which was then incorporated in PVDF to prepare PVDF/MoS2@ZnO piezoelectric composite film. The effect of various contents of ZnO on its structure and properties was emphatically discussed, as well as the mechanical energy collection and sensing performance. The results show that ZnO has been deposited on the surface of MoS2 nanosheet to form heterostructure (MoS2@ZnO), as well as that the MoS2@ZnO can effectively promote the transformation from α phase to β phase in PVDF, by which the content of β phase can be increased from 6.2 ± 2.5 % to 54.3 ± 2.7 %. It also exhibits excellent mechanical performance and flexibility with the tensile strengthen of 37.64 ± 5.12 MPa and elongation at break of 9.77 ± 1.57 %. The longitudinal piezoelectric constant (d33) of the composite film reached a maximum value of 31 ± 4 pC·N-1. The open-circuit voltage (VOC) and short-circuit current (ISC) of PVDF/MoS2@ZnO piezoelectric composite film reach as high as 6.22 V and 528 nA under the acting force of 100 KPa, respectively. It can charge a 1.0 μF commercial capacitor to 1.81 V in 400 s. Finally, a flexible piezoelectric sensor was fabricated to collect the pressure signals induced from human body movement (the bending of fingers, wrists and elbow joints), presenting excellent sensitive piezoelectric response with the VOC of about 0.41 V, 0.22 V and 0.32 V, respectively. The found performance indicates its feasibility for the application in wearable intelligent devices.

Fabrication method of flexible strain sensors with CNTs and solvents

Flexible strain sensors have received a lot of attention for their various applications, such as electronic skins, healthcare devices, and human-machine interactions. In many studies of manufacturing flexible strain sensors using carbon nanotubes (CNTs), various solvents are used to disperse CNTs. However, most studies lack explanation of the rationale for using specific solvent, which is mainly used to disperse CNTs and make CNT solution. There are studies dealing with the degree of dispersion in specific solvent of CNTs, but these studies lack information on solvents in the sensor manufacturing process. Therefore, researchers have difficulty in determining which solvent to use for CNT dispersion in their process because solvent selection varies depending on the sensor manufacturing method. Thus, the dispersion stability of CNT solutions with several solvents and the characteristics of CNT sheets made from each CNT solution were quantitatively compared. Then, the solvent suitable for an acrylic mold as well as having high dispersion stability was selected. Moreover, the flexible CNT strain sensor is developed by transferring CNTs to a flexible substrate. This sensor can be stretched up to 150% (linearity R=0.998), and the gauge factor was 26.7. It is expected to be used in various research of wearable sensors or human motion monitoring using CNT dispersion.

Piezoresistive Properties of 3D-Printed Polylactic Acid (PLA) Nanocomposites.

An increasing interest is focused on the application of 3D printing for sensor manufacturing. Using 3D printing technology offers a new approach to the fabrication of sensors that are both geometrically and functionally complex. This work presents the analysis of the 3D-printed thermoplastic nanocomposites compress under the applied force. The response for the corresponding resistance changes versus applied load is obtained to evaluate the effectiveness of the printed layer as a pressure/force sensor. Multi-walled carbon nanotubes (MWNT) and high-structured carbon black (Ketjenblack) (KB) in the polylactic acid (PLA) matrix were extruded to develop 3D-printable filaments. The electrical and piezoresistive behaviors of the created 3D-printed layers were investigated. The percolation threshold of MWNT and KB 3D-printed layers are 1 wt.% and 4 wt.%, respectively. The PLA/1 wt.% MWNT 3D-printed layers with 1 mm thickness exhibit a negative pressure coefficient (NPC) characterized by a decrease of about one decade in resistance with increasing compressive loadings up to 18 N with a maximum strain up to about 16%. In the cyclic mode with a 1 N/min force rate, the PLA/1 wt.% MWNT 3D-printed layers showed good performance with the piezoresistive coefficient or gauge factor (G) of 7.6 obtained with the amplitude of the piezoresistive response (Ar) of about -0.8. KB composites could not show stable piezoresistive responses in a cyclic mode. However, under high force rate compression, the PLA/4 wt.% KB 3D-printed layers led to responses of large sensitivity (Ar = −0.90) and were exempt from noise with a high value of G = 47.6 in the first cycle, which is a highly efficient piezoresistive behavior.

A Single-material-printed, Low-cost design for a Carbon-based fabric strain sensor

The manufacturing of flexible strain sensors for wearable electronics usually requires different conductive materials for the sensing part and the connection part. This increases the complexity, cost, and performance issues due to the mismatch of the thermo-electro-mechanical properties of the materials. Herein, a new design scheme using a single conductive material is presented for a low-cost mass-producible fabric strain sensor, where a carbon/silicone nanocomposite is screen-printed to make both parts. By exploring the dimension effect and modelling of the conductive tracks, and adopting a large difference of over 100 times in aspect ratio, this research makes the electrical response of the fabric strain sensor depend almost exclusively on the sensing part, while its connection part has a low resistance. The sensor exhibits outstanding performance with a wide working range (60% strain), adequate linearity, long fatigue life (∼50,000 cycles), and mechanical robustness, rendering it suitable for human body movement detection. Moreover, the manufacturing process is simple and low-cost ($11 per m2). Thus, the new design scheme overcomes the mismatch issue and provides an important reference value for the design of flexible resistive sensors working in a high resistance range, from ∼ 100 KΩ to several MΩ.

(Digital Presentation) Printed Wearable Electrochemical Sensor for Monitoring Human Performance Markers during Human Spaceflight

Additive manufacturing technologies are being explored by NASA for the in-space manufacturing of sensors and electronics. Additive manufacturing directly addresses the logistic challenge for long-duration human spaceflight missions while also offering a high degree of customization and tailorability. To ensure the health and safety of crew members during long duration missions, it can be advantageous to develop human health diagnostic tools that can be manufactured during those missions. Here we report the development of a wearable and fully printed electrochemical sensor for the detection of human performance markers in sweat.1 The sensor’s fabrication is complimentary with in-space manufacturing for an on-demand and hands-free fabrication and is comprised of commercial and custom carbon, gold and silver inks on a polyimide substrate to make a flexible, 3-electrode electrochemical sensor, shown in Figure 1. Sensor readout is performed using standard electrochemical procedures via a miniaturized, custom potentiostat. The initial prototyped printed electrochemical sensors demonstrate good electrochemical performance and high mechanical stability while also displaying low batch to batch variability. Our goal is to create a highly adaptable and versatile approach that utilizes fabrication processes consistent with in-space manufacturing, thus enabling the manufacture of point-of-care devices during flight.Reference Brasier, N. & Eckstein, J. Sweat as a Source of Next-Generation Digital Biomarkers. Digit. Biomarkers 3, 155–165 (2019). Figure 1

The electronic properties and adsorption mechanism of Agn, Aun (n = 1–4) modified GeSe monolayer towards hazardous gases (H2S, NH3, NO2 and SOF2): A first-principles study

In this study, the first-principles were adopted to investigate adsorption behaviour and electrical properties of Agn, Aun (n = 1–4) modified GeSe monolayer towards hazardous gases (H2S, NH3, NO2, SOF2). The contributions of transition metal nanoparticles to the surface modification and gas adsorption behaviour of the two-dimensional material GeSe were analysed. We have studied the adsorption and sensing properties between the target gas molecules and GeSe substrate through the analysis of the adsorption energy, charge transfer, differential charge density, and density of states. In order to better simulate the mixture under the pragmatic doping situation, the number of gold and silver nanoparticles doped in this study ranged from 1 to 4, meanwhile the most stable computational structures were selected based on the binding energy. The results show that Agn, Aun cluster modifications can improve the electrical conductivity of GeSe monolayer, and the vibrant sites provided by the dopants significantly enhance the gas-sensitive response of the pristine GeSe to these hazardous gases. The adsorption type changes from initial non-spontaneous reactions to physico chemical adsorption, and the ideal adsorption energy make the doped system possess good adsorption and desorption properties. In addition, compared with peaceable interreaction of SOF2 adsorption system, Agn, Aun-GeSe has strong capturing ability for NO2. The results provide a theoretical basis for further manufacture of industrial toxic gas sensors and online monitoring of SF6 insulated equipment.

Inkjet printed Ta2O5 on a flexible substrate for capacitive pH sensing at high ionic strength

Many pH sensors on the market today have specific limitations, such as the large and fragile construction of glass electrodes, or the complicated manufacturing processes of silicon-based devices including ion-sensitive field-effect transistors (ISFETs). Furthermore, most pH sensors require a stable reference electrode, which is difficult to miniaturize. In applications where the solution properties are largely understood, the use of an impedimetric sensor without a reference electrode may be sufficient, thereby simplifying the manufacturing of such sensors. In this work, inkjet printed and flash lamp annealed Ta2O5 on interdigitated electrodes, with an approximate sensor area of 4 mm × 4 mm, is investigated as a capacitive pH sensing layer in 0.5 M alkali chloride buffer solutions. By using the equivalent circuit of the insulator-electrolyte interface, the double layer capacitance is shown to decrease with an increase in pH within the range of pH 2 to pH 9, and agrees with prior results for anodic Ta2O5. When using the device as a sensor in both 0.5 M NaCl and 0.5 M LiCl aqueous solutions, the change in capacitance at 100 Hz is approximately − 110 nF/pH. Apart from pH sensing, these results may also prove informative in other applications, such as electrolytic capacitors, electrophysiology, and battery anodes in aqueous electrolyte. Moreover, the use of flexible, gold metallized polyethylene terephthalate (PET) foils as the sensor substrate potentially allows for large-scale production via roll-to-roll manufacturing, and further permits for use of the sensor in flexible applications such as goods packaging.

Recent Advances in Touch Sensors for Flexible Wearable Devices.

Many modern user interfaces are based on touch, and such sensors are widely used in displays, Internet of Things (IoT) projects, and robotics. From lamps to touchscreens of smartphones, these user interfaces can be found in an array of applications. However, traditional touch sensors are bulky, complicated, inflexible, and difficult-to-wear devices made of stiff materials. The touch screen is gaining further importance with the trend of current IoT technology flexibly and comfortably used on the skin or clothing to affect different aspects of human life. This review presents an updated overview of the recent advances in this area. Exciting advances in various aspects of touch sensing are discussed, with particular focus on materials, manufacturing, enhancements, and applications of flexible wearable sensors. This review further elaborates on the theoretical principles of various types of touch sensors, including resistive, piezoelectric, and capacitive sensors. The traditional and novel hybrid materials and manufacturing technologies of flexible sensors are considered. This review highlights the multidisciplinary applications of flexible touch sensors, such as e-textiles, e-skins, e-control, and e-healthcare. Finally, the obstacles and prospects for future research that are critical to the broader development and adoption of the technology are surveyed.

Microfluidics-assisted electrospinning of aligned nanofibers for modeling intestine barriers.

During electrospinning, the fibers deposited on the collector are usually randomly oriented in a disordered form. Researchers hope to generate periodic structures to expand the application of electrospinning, including improving the sensing properties of electronic and photonic devices, improving the mechanical properties of solid polymer composites and directional growth of human tissues. Here, we propose a technique to control the preparation of aligned foodborne nanofibers by placing dielectric polymers on microfluidic devices, which does not require the use of metal collectors. This study was conducted by introduced PEDOT:PSS polymer as a ground collector to prepare aligned foodborne nanofibers directly on the microfluidic platform. The fluidity of the electrolytic polymer collector makes it possible to shape the grounding collector according to the shape of the microcavity, thus forming a space adjustable nanofiber membrane with a controllable body. The simplicity of dismantling the collector also enables it extremely simple to obtain a complete electrospun fiber membrane without any additional steps. In addition, nanofibers can be easily stacked into a multi-layer structure with controllable hierarchical structures. The Caco-2 cells that grow on the device formed a compact intestinal epithelial layer that continuously expresses the tightly bound protein ZO-1. This intestinal barrier, which selectively filters small molecules, has a higher level of TEER, reproducing intestinal filtration functions similar to those of in vivo models. This method provides new opportunities for the design and manufacture of various tissue scaffolds, photonic and electronic sensors.

Textile-based pressure sensor arrays: A novel scalable manufacturing technique

Soft pressure sensors have sparked a lot of interest over the last decade because of their applications in human motion recognition, object detection, and human–computer interaction. However, their mass production and availability to end users are limited due to the complex and time-consuming steps. The scalability of working range for various applications is also a critical challenge. Therefore, a laborless, rapid, and scalable manufacturing technique for capacitive-based soft pressure sensors with high sensitivity and high working range is proposed in this work. The novel manufacturing method enables manipulation of sensor properties by varying production parameters based on specific application needs. The proposed sensor's electrode is made of conductive knit fabric, and the dielectric layers are made of thermoplastic polyurethane (TPU) sheets. As a result of the novel approach, it is possible to generate scalable air gaps between electrodes and dielectric layers to capture low pressures of less than 1 kPa. The usage of multi-layer TPU sheets also increases the working range of sensors up to 1000 kPa. Here, the proposed technology is successfully applied to create several sensor mats for different purposes such as improved gesture and shape recognition, and interactive gaming mats for children. • Simple and fast manufacturing of a novel textile pressure sensor. • Scalable with desired pattern of the sensor mat. • Adjustable sensitivity and wide working range from 1 kPa to 1000 kPa. • Pressure mapping for e-textiles, interactive software and human gesture recognition.

Multiwall Carbon Nanotubes: A Review on Synthesis and Applications

:MWCNTs are elongated cylindrical nanoobjects made of sp2 carbon. They have a diameter of 3–30 nm and can grow to be several centimetres long. Therefore, their aspect ratio can range between 10 to 10 million. Carbon nanotubes are the foundation of nanotechnology. It is an exceptionally fascinating material. CNTs possess excellent properties, such as mechanical, electrical, thermal, high adsorption, outstanding stiffness, high strength and low density with a high aspect ratio. These properties can be useful in the fabrication of revolutionary smart nanomaterials. The demand for lighter and more robust nanomaterials in different applications of nanotechnology is increasing every day. Various synthesis techniques for the fabrication of MWCNTs, such as CVD, arc discharge, flame synthesis, laser ablation, and spray pyrolysis, are discussed in this review article, as are their recent applications in a variety of significant fields. The first section presents a brief introduction of CNTs, and then the descriptions of synthesis methods and various applications of MWCNTs in the fields of energy storage and conversion, biomedical, water treatment, drug delivery, biosensors, bucky papers and resonance-based biosensors are provided in the second section. Due to their improved electrical, mechanical, and thermal properties, MWCNTs have been extensively used in the manufacturing and deployment of flexible sensors.

Green Manufacturing of Flexible Sensors with a Giant Gauge Factor: Bridging Effect of CNT and Electric Field Enhancement at the Percolation Threshold.

Toxic organic solvents are commonly used to disperse nanomaterials in the manufacturing of flexible conductive composites (e.g., graphene-PDMS). The dry-blended method avoids toxic organic solvent usage but leads to poor performance. Here, we proposed an innovative manufacturing method by adapting the traditional dry-blended method, including two key steps: minor CNT bridging and high-frequency electric field enhancement at the percolation threshold of graphene-PDMS. Significant improvement was achieved in the electrical conductivity (1528 times), the giant gauge factor (>8767.54), and the piezoresistive strain range (30 times) over the traditional dry-blended method. Further applications in measurements of culturing rat neonatal cardiomyocytes and mouse hearts proved that the proposed method has great potential for the manufacturing of nontoxic flexible sensors.

Evaluation of conductivity and piezo-impedance response of VACNTs/PDMS nanocomposite-based strain sensors under small deformations

The vertically aligned multi-walled carbon nanotubes (VACNTs) / polydimethylsiloxane (PDMS) nanocomposite-based strain sensors presented in this study show different behavior depending on catalyst concentrations for VACNT growth. Under static tensile load, the sensor with lower catalyst concentration shows a high gauge factor (GF~1400), whereupon tunneling effect is the mechanism that dictates the sensitivity. For higher concentrations, the GF decreases (GF~40) and shows an ohmic conduction. Morphological examinations showed VACNTs are homogeneously and randomly distributed as clusters with CNT bridging in the PDMS polymer matrix. Based on dielectric impedance (DI) and direct current (DC) electrical analysis, it was possible to identify that cut-off frequency (fc) increases with VACNTs concentration. Cut-off frequency can also define high sensitivity VACNT sensors with lower VACNT density. When compared with dispersed MWCNT sensors, VACNTs have a reduced fc due to the larger internal resistance variation associated with the high tunneling effect. This effect associated with the high sensitivity of the VACNT/PDMs sensors makes it a key factor to understand the mechanisms responsible for increasing the sensitivity and manufacturing of high GF nanocomposite stretchable sensors.

Additive manufacturing of capacitive humidity sensors by screen printing for condition monitoring of FRP composites

Screen printing as a method of additive manufacturing applicable for the production of highly sensitive humidity sensors is presented. For this purpose, manufacturing, benchmarking and optimization of sensitive micro-composite dielectric paste systems suitable for screen printing are demonstrated. Furthermore, commercially available silver paste systems were rheologically and electrically characterized and benchmarked. Thereby bulk silver conductivities of up to 15 % were measured with average layer thicknesses in the range between 3 - 10 μm and an occurring surface roughness Ra between 0.7 - 3.7 μm. The printed sensors capacitance was measured along with the characterization of its humidity sensing capability. The capacitance of the printed sensors varied between 6.2 - 8.5 pF depending on the layer thickness of the micro-composite dielectric materials and increased up to 26 pF while detecting 90 % relative humidity. Differences between water molecule absorption and desorption are determined by the occurring hysteresis between the detection of increasing and decreasing humidity. Malfunctions of the sensors due to the arising cross contact between top and bottom electrode could be addressed by varying the layer thickness or selection of materials.

Preparation and characterization of self-healable and wearable hydrogels with ultrasensitive sensing performances

Conductive hydrogels with multifunction have received significant attention in the field of wearable electronic devices, especially in strain sensors and pressure sensors. The high sensor sensitivity, flexibility and mechanical strength are the top three critical factors for manufacturing of trustworthy sensors for practical applications. However, the conductive hydrogels are subjected to some limitations due to the lack of self-repair ability when damaged by external force, the low electrical conductivity and weak mechanical strength. To address these issues, multifunctional conductive hydrogels incorporating MXene nanosheets and lignin amine-silver nanoparticles (LA-Ag NPs) were constructed via a dynamic redox system. Benefiting from the introduction of MXene and LA-Ag NPs, the hydrogels demonstrated strong adhesiveness, self-healing property and high conductivity. Notably, the epidermal sensors demonstrated high sensitivity over a broad range as both strain sensor (GF = 9.17) and pressure sensor (S = 0.33 kPa−1).

An Ultra-Low-Power Strain Sensing Node for Long-Range Wireless Networks in Carbon Nanotube-Based Materials

The application of flexible electronics to device-engineering technologies has enabled the manufacture of low-cost, lightweight, extensible, and foldable sensors. However, despite the efficient response of composite materials for the detection of signal stimuli reported in the state-of-art literature, there is an area of opportunity for the implementation of ultra-low-power wireless sensor networks (WSN) with novel flexible materials in precision medicine, structural health monitoring, environmental sensing, wearables and applications based on the Internet of Things (IoT). This article proposes a portable strain sensing node based on multiwall carbon nanotubes (MWCNTs)/polypropylene(PP) composites for Long-Range (LoRa) wireless networks with IoT connectivity. The nanostructured sensor node with 4 wt% MWCNTs shows high piezoresistive sensitivity with gage factors of ~ 4.5. A system identification problem is conducted following a constrained optimization model, which estimates the sensor errors due to nonlinearity and system parameters, providing a stable strain response with high accuracy. An energy management strategy is also implemented for the efficient integration of a microcontroller unit in combination with a wireless LoRa communication transceiver, enabling the utilization of flexible composite materials into a wireless nanostructured sensing network with ultra-low-power consumption of 0.8705 mW. The experimental results of the MWCNT/PP strain sensing node show the feasibility for a variety of IoT-WSN applications.

Design, Manufacture, Test and Experiment of Six-Axis Force Torque Sensor for Chinese Experimental Module Manipulator.

A novel six-axis force/torque sensor (F/T sensor) for an Experimental Module Manipulator (EMM) in the Chinese Space Station (CSS) is developed in this paper. First, we designed the elastomer structure of the F/T sensor and used the analytical method and the finite element method to analyze the strain, in order to accomplish the strain gauges’ layout. Then, the electrical system was designed, which mainly realizes the acquisition of force/torque information, temperature and serial communication with the end effector (EE). Following this, we analyzed and designed the adaptability of the F/T sensor to the space environment. After this, the manufacturing process of the sensor was introduced in detail, and the F/T sensor was calibrated by a pulley weight system. Finally, the sensor was tested on the space environment adaptability of mechanical vibration and thermal vacuum on the ground. The test results show that the developed sensor has the ability to accurately measure three-dimensional force and three-dimensional moment information on orbit, which provides necessary conditions for the on-orbit fine operation of EMM.

Capacitive Humidity Sensors Based on Nanocellulose for Biodegradable Electronics

The humidity sensor is an important device used in many areas of human life, such as agriculture, medicine, industry, meteorology and more. Most often, synthetic polymers are used for the manufacture of humidity sensors, which after the end of their operation are accumulated in the form of electronic waste, polluting the environment. Currently, biodegradable polymers are in great demand. Such materials include nanocellulose, which can be made from both wood and plant raw materials. It has already been proven that nanocellulose is a promising material for use in humidity-sensitive devices. However, it was not clear the effect of sensitive film’s thickness on the characteristics of humidity sensors. In this work, capacitive humidity sensors based on nanocellulose were fabricated. Nanocellulose (NC) was obtained from reeds by the TEMPO method. The moisture-sensitive layer of NC was applied by dripping. Static (sensitivity, response, hysteresis) and dynamic (response time, recovery time, short- and long-term stability) characteristics of the manufactured humidity sensors were measured in dependence on mass of NC film (from 0.3 to 3.6 mg) and test signal frequency (100 Hz and 1000 Hz). The response of the sensors was increased with the weight of moisture-sensitive NC film and reached 1412 nF at 100 Hz (783 nF at 1000 Hz) for the sample of 0.6 mg NC, and then decreased with further increase in mass. The sensitivity of the sensors varied similarly, but the maximum value was observed for the sample with a mass of 1.8 mg and was 0.161 (%RH)-1 for 100 Hz (0.165 (%RH)-1 for 1000 Hz). The shortest response time had the sample with the lowest mass of moisture-sensitive film (100 s). With a further increase in the mass of moisture-sensitive NC film, the response and recovery time increased monotonically. Also, the sample with the lowest mass of the moisture-sensitive layer shows the lowest value of hysteresis (0.1%) and also increased with the increasing mass of the moisture-sensitive layer. In the study of short-term stability, samples weighing from 0.3 to 0.6 mg showed a significantly higher level of fluctuations (10 - 20%) compared to samples with a weight of the moisture-sensitive layer of 1.8 - 3.6 mg (1 - 4%). So, you should use nanocellulose film of larger mass (1.8… 3.6 mg) in order to improve the sensitivity and short-term stability of the devices. In view of the responce and recovery time as well as repeatability of the sensor characteristics, thin nanocellulose films (0.3… 0.5 mg) should be used. The direction of further research is to improve the long-term stability of the devices, in particular by modifying the nanocellulose film with adding certain impurities.

Carbon Nanotubes‐Based 3D Printing Ink for Multifunctional “Artificial Epidermis” with Long‐Term Environmental Stability

Abstract3D printing is a rapidly developing field because it has been widely used in the rapid design and manufacturing of flexible sensors to meet the needs of complex soft structures and devices. In this study, a composite hydrogel ink composed of polyvinyl alcohol, silk fibroin, conductive polymer, and carbon nanotubes is designed,and using 3D printing technology an “artificial epidermis” with long‐term environment stability and self‐healing ability is created. In addition, the “artificial epidermis” also has the multifunctional characteristics of sensing pressure, strain, temperature, and humidity. It has a wide pressure (0–165 kPa), strain (0–355%), temperature (−20–68 °C) and humidity (45–85%) sensing range and high sensitivity. While detecting the tiny movements of the human body, after self‐healing, the device can fully restore its sensing capabilities and perform accurate human monitoring. Furthermore, it can also monitor changes in temperature and humidity, distinguish between hot and cold water, and perform detection of water droplets. Customized 3D printing of flexible electronic devices has opened up new ways for the biological integration of various sensors in wearable electronic systems and the application of advanced bionic skin.

Electrochemical sensor for rapid detection of fentanyl using laser-induced porous carbon-electrodes.

The growing pervasiveness of opioid-based drugs such as fentanyl and its analogs represent a foremost hazard to the civilian population and burden on the first responders and clinicians. Thus, to enable a rapid and low-cost surveillance system to detect fentanyl in a non-ideal environment, we demonstrate the use of laser-induced nano-porous carbon structures directly onto commercially available polyimide sheets for rapid and cost-effective manufacturing of electrochemical sensors for fentanyl detection. The porous carbon surface instigated by various laser energy densities was analyzed towards morphological, vibrational, and fentanyl sensing properties. The results showed that laser carbonized electrode (LCE) prepared with 31J/cm2 laser energy densities showed the highest level of porosity, surface roughness, and thereby enhanced sensitivity towards fentanyl detection by square-wave voltammetry (SWV) with a 1µM limit of detection. This new disposable sensor strip offers an information-rich electrochemical fingerprint of fentanyl oxidation at + 0.526V (vs Ag/AgCl) on the surface of laser carbonized electrodes with high linear (R2 = 0.99) sensitivity (0.025 µA⋅µM-1⋅cm-2) and reproducibility (RSD = 5%), within the clinically relevant working range of 20-200µM with similar performance in both PBS and serum samples. The laser carbonized electrode surface was further found to be selective towards fentanyl concentrations in the presence of various cutting agents. This technology could provide a new route towards scalable manufacturing of cost-effective sensors for rapid detection of opioid misuse and potentially save the lives from systemic side effects.