Sensor Manufacturing Research Articles

High-performance LPG sensing behaviour of CoCr2-xCexO4 (x = 0 to 0.02) for sensor applications.

For the first time, the influence of Cerium (Ce3+) on the structural, microstructural, Fourier infrared spectroscopy, and LPG sensing behaviour of CoCr2-xCexO4 (CoCrCe) is described in this study. The solution combustion technique was used to create the CoCrCe samples. All samples were sintered for 3h at 600°C to achieve a pure crystalline nature free of impurities. The production of cubic spinel structures with typical crystallite sizes smaller than 16nm is confirmed by X-ray diffraction. Because compressive lattice strain is created when Ce3+ ions are replaced by Cr3+ ions, we discovered reducing the lattice parameter. Further samples were analysed using the FTIR technique to learn about the octahedral and tetrahedral stretching bands, which confirmed the ferrite structure was free of impurities. Scanning Electron microscopy was used to examine the samples' microstructures. All of the samples were determined to be very porous. Elemental analysis was performed using energy dissipative spectra, which confirmed the presence of all elements in the samples. 2-mol% Ce3+has the best gas sensing characteristics of any Ce concentration. Furthermore, the thin film based on CoCr1.98Ce0.02O4 may be employed as a chemiresistive gas sensor to detect LPG (10-1000ppb) at room temperature. On LPG exposure, the constructed gas sensor demonstrates greater gas sensitivity in the order of 98% at 500ppb, with higher stability, rapid response, and recovery time in the order of 60s and 75s, respectively. This study reports for the first time on the creation of an LPG gas sensor device that operates at room temperature and has high sensitivity. Because of their high gas sensitivity, rapid reaction and recovery times, and long-term stability, these material gas sensors might be ideal materials for the manufacture of gas sensors devices for the detection of LPG low concentration (ppb level).

Chitosan and its applications in oenology

This paper reviews the main applications of the biopolymer chitosan, the main derivative of chitin, a material usually obtained from natural sources accessible at low cost, i.e., industrial wastes from fisheries. Due to its natural origin, which confers biodegradability and biocompatibility properties, in addition to its low toxicity, chitosan has been gaining attention in numerous sectors, such as agriculture, food, medicine, pharmaceuticals, etc., including also important oenological applications due to its potential as a green alternative to the use of sulphite. Among the many applications that can be generated from these materials in the wine-making area, their use has been reported for the clarification of must; in the preparation of films for the removal of contaminants, whether organics such as ochratoxin A or inorganics such as some metal ions and their salts; the control of turbidity caused by protein precipitation; the encapsulation of yeasts of oenological interest and enzymes for the control of adverse microorganisms such as Brettanomyces; the manufacture of sensors and nanosensors for the quantification of contaminants, the quality control of starting materials and final products, the optimisation of fermentation processes, the monitoring of storage conditions, etc. As a result of this review, significant development of the applications of this material in the oenological area can be expected, especially due to the possibilities of preparing new derivatives, including the great variety of these that have been recently proposed through click reactions, as well as the growing incursion of chitosan in nanobiotechnology.

Highly compressible and thermal insulative conductive MXene/PEDOT:PSS@melamine foam for promising wearable piezoresistive sensor

With the rapid development of intelligent wearable electronic devices, highly compressible porous piezoresistive sensors are in imperative demand. However, the robustness of conductive coating that affects the stability and durability of porous piezoresistive sensors still needs to be solved urgently. In this work, a flexible conductive MXene/PEDOT:PSS@Melamine foam (MPMF) piezoresistive sensor was designed and prepared by simply dip-coating it in MXene and PEDOT:PSS mixed solution. Here, foam skeleton was first treated with PDA to improve its hydrophilicity and enhance the interfacial interaction with the functional groups of MXene nanosheets. More importantly, the usage of PEDOT:PSS can fix the MXene nanosheets tightly and construct synergistic conductive network between them, obtaining stable, robust, and highly conductive coating. Based on the contact effect between the adjacent conductive skeleton, the prepared MPMF sensor displays excellent piezoresistive sensing performances, which includes a wide working range (up to 80% compression strain, 60 kPa pressure), high sensitivity (0.30 kPa−1 in the pressure range of 12–60 kPa), and stable sensing pattern over 1000 compression cycles. All these merits make the sensor capable of detecting various human motions and pressure/location distribution of different items when assembled into an electronic skin. In addition, excellent thermal insulation property under different temperature conditions was also observed for MPMF due to the existence of special porous structures, providing necessary thermal protection when served as a wearable sensor. This research provides a convenient, simple, and cost-effective method for the manufacture of high-performance porous piezoresistive sensor.

A method for evaluating camera auto-focusing performance using a transparent display device

With the development of various autofocusing (AF) technologies, sensor manufacturers are demanded to evaluate their performance accurately. The basic method of evaluating AF performance is to measure the time to get the refocused image and the sharpness of the image while repeatedly inducing the refocusing process. Traditionally, this process was conducted manually by covering and uncovering an object or sensor repeatedly, which can lead to unreliable results due to the human error and light blocking method. To deal with this problem, we propose a new device and solutions using a transparent display. Our method can provide more reliable results than the existing method by modulating the opacity, pattern, and repetition cycle of the target on the transparent display.

Influence of instrument parameters on the electrochemical activity of 3D printed carbon thermoplastic electrodes

3D printing provides a reliable approach for the manufacture of carbon thermoplastic composite electrochemical sensors. Many studies have explored the impact of printing parameters on the electrochemical activity of carbon thermoplastic electrodes but limited is known about the influence of instrument parameters, which have been shown to alter the structure and mechanical strength of 3D printed thermoplastics. We explored the impact of extruder temperature, nozzle diameter and heated bed temperature on the electrochemical activity of carbon black/poly-lactic acid (CB/PLA) electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were conducted using standard redox probes. The electrode surface and cross-section of the electrode was visualised using scanning electron microscopy. We found that using extruder temperatures of 230 °C and 240 °C improved the electrochemical activity of CB/PLA electrodes, due to an increase in surface roughness and a reduction in the number of voids in-between print layers. Nozzle diameter, heated bed temperature of different 3D printers did not impact the electrochemical activity of CB/PLA electrodes. However high-end printers provide improved batch reproducibility of electrodes. These findings highlight the key instrument parameters that need to be considered when manufacturing carbon thermoplastic composite electrochemical sensors when using 3D printing.

Direct fabrication of flexible tensile sensors enabled by polariton energy transfer based on graphene nanosheet films

A fundamental problem in the direct manufacturing of flexible devices is the low melting temperature of flexible substrates, which hinders the development of flexible electronics. Proposed here is an electron-cyclotron-resonance sputtering system that can batch-fabricate devices directly on flexible substrates under a low temperature by virtue of the polariton energy transfer between the plasma and the material. Flexible graphene nanosheet-embedded carbon (F-GNEC) films are manufactured directly on polyimide, polyethylene terephthalate, and polydimethylsiloxane, and how the substrate bias (electron energy), microwave power (plasma flux and energy), and magnetic field (electron flux) affect the nanostructure of the F-GNEC films is investigated, indicating that electron energy and flux contribute to the formation of standing graphene nanosheets in the film. The films have good uniformity of distribution in a large size (17 mm × 17 mm), and tensile and angle sensors with a high gauge factor (0.92) and fast response (50 ms) for a machine hand are obtained by virtue of the unique nanostructure of the F-GNEC film. This work sheds light on the quantum manufacturing of carbon sensors and its applications for intelligent machine hands and virtual-reality technology.

High sensitivity temperature sensor based on enhanced Vernier effect through two parallel Fabry-Perot cavities.

In this paper, an enhanced Vernier effect temperature sensor based on two parallel Fabry-Perot interferometers (FPIs) is proposed and demonstrated experimentally. Among them, F P I 1 is composed of a single-mode fiber (SMF), a quartz capillary, and AB glue filled in the capillary. F P I 2 is formed by filling a capillary with polyimide (PI) solution and inserting two-segment SMF from both sides of the capillary. Since AB glue and PI have good thermal sensitivity, F P I 1 and F P I 2 are highly sensitive to temperature. Due to their different structures, the temperature sensitivity of F P I 1 is negative, and that of F P I 2 is positive. When F P I 1 and F P I 2 with similar free spectral range are connected in parallel, they will act as reference cavities for each other, resulting in an enhanced Vernier effect, which enlarges the sensitivity of the sensor more. In the temperature range of 40°C-58°C, the temperature sensitivity of the sensor is as high as -13.09n m/∘ C, and the fitting coefficient is 0.9974. The experimental results show that in the enhanced Vernier effect sensor structure, only two FPIs with opposite temperature sensitivity are required, which does not increase the difficulty and cost of sensor manufacturing. In addition, the sensor has good stability and repeatability.

Principle and Application of Flexible Pressure Sensors

Flexible pressure sensors are widely used in many ways, including health care and machine sensors. Compared with the traditional flexible pressure sensor, flexible pressure sensor has quality is light, easy to carry and deformation degree higher advantages are modern science and technology advanced has broad prospects for the development of technology products. In recent years, Remarkable progress has been made in the field of flexible pressure sensors. However, it is still a big challenge to realize the high resolution, high sensitivity, fast response, low-cost manufacturing and complex signal detection of flexible pressure sensors. This paper will introduce the mechanism of the flexible pressure sensor and improve the sensitivity by using the microstructure and the practical application. The research in this paper will have a very important value for the research and application of the flexible pressure sensor.

Disposable Wearable Sensors Based on Nanocellulose for Biomedical Applications

Monitoring of human motor and muscle activity is used in many areas, from prosthetics during rehabilitation to training monitoring of athletes. Sensors for these tasks are usually made of flexible polymers and require recycling after the expiration date. Nanocellulose (NC) can be used as a biodegradable base for this type of sensor. The development of low-cost disposable sensors that do not require disinfection and cleaning is relevant. NC is a composite nanoscale structure of cellulose fibers (fibrils) with a high aspect ratio. The paper aim is to develop disposable wearable biodegradable bend sensors based on nanocellulose using vacuum synthesis methods and the study of their characteristics. Nanocellulose was synthesized by the TEMPO method. The sensors were created by means of magnetron sputtering of Ti/Ni or Cr/Ni thin films at the surface of nanocellulose. Measuring stand was developed to determine the change in resistance due to the bending of the sensor. It’s mechanical part consists of an elastic deformation plate made of high-alloy steel, which can be bent using a micrometric screw. The change in resistance is linearly related to the elongation of the measured sample. A Wheatstone bridge and a 24-Bit ADC HX711 were used to measure the change in resistance. During testing of the sensor for analysis of muscle activity, the sensor element was attached to the human skin with the help of medical glue BF-6. The obtained sensors were tested for biodegradability. The samples were placed in the ground at a depth of 20-30 mm. The mass of nanocellulose samples was measured using a high-precision digital balance EDIS 50 (50/0.001 g) with a built-in level. The optimal ratio of the value of sensitivity and reversibility is observed in the range of the nominal resistance of the nickel film from 10 to 100 Ohms. This is due to an increase in the surface area of ​​the Ni film, which leads to an increase in sensitivity, but at the same time there is a decrease in the repeatability of the characteristics due to a greater influence of the heterogeneous structure of nanofibrillated cellulose. In addition, sensors with different buffer layer materials - Ti and Cr - were selected for testing. For titanium-based sensors, the maximum sensitivity coefficient is 0.312%, while the deviation of the sensor signal after one bending-unfolding cycle (reversibility) is less than 0.001%. Chromium-based sensors have significantly higher sensitivity (0.9753%), but worse reversibility (7.14%). Sensors based on the Cr buffer layer showed poorly reproducible results in the cyclic mode of operation, namely: there are significant fluctuations in the signal amplitude (up to 50-60%) already after the second bending-unfolding cycle. Therefore, despite the high sensitivity of such sensors, they are unsuitable for analyzing human motor and muscle activity/ The sensors based on the Ti buffer layer showed good response (2.5-3%) and good repeatability and resistance to cyclic bending (30 times). It can be seen that the obtained dependencies are approximated by a linear law. Some deviation from linearity is obviously related to the inhomogeneity of the Ni thin film. Also, the sensors showed a good loss of mass (40% in 9 weeks) during the biodegradability test, which confirms their ability to decompose under the influence of atmospheric phenomena. So, in this work, disposable wearable sensors on a nanocellulose substrate were synthesized for the evaluation of motor and muscle activity of a person. It was found that such sensors can be used to test of finger and biceps movement during at least 10-30 full flexion-extension cycles. For test of elbow movement, it is planned to synthesize a high-elastic composite material based on nanocellulose and bioelastic material (for example, polyvinyl alcohol). Thus, the proposed sensor manufacturing technology makes it possible to obtain cheap, light, flexible disposable wearable sensors that do not require further disposal after the end of operation.

Integration of Autonomous Cars with the Infrastructure of the City of St. Petersburg: Study of the Problems

The article explores the problems of introducing autonomous cars (AC) into the transport infrastructure of St. Petersburg. The main problems among others comprise road technical condition and road equipment, security of data transmission, lack of technical capacity regarding data transfer rate, lack of regulation regarding technical issues. The study contains an assessment of the technical condition of roads as well as of presence of road markings necessary for positioning of AC on the road.The suggested listing of the main parameters of road pavement condition substantiates the necessity to obtain relevant data and to equip the road system with appropriate sensors. The main areas important to ensure data transmission security during the design and construction of AC systems as described comprise security of collecting, transmitting, and processing data by AC systems, driver authentication, security of data transmission from road infrastructure. The study of the problem of data transfer rate incorporated a comparative analysis of the parameters of 4G technology, which is currently used by the infrastructure of telecom operators, and 5G technology, followed by the brief analysis of the barriers to adoption of 5G technology in Russia. The investigation of the existing regulatory and technical framework governing the operation of AC on public roads has identifi a few key issues that are currently not governed by legislative acts or regulations.The consideration of the problem of responsibility of road users has given ground to suggest that the responsibility must be extended not only to the owners of AC, but also to other participants in the process (manufacturers of AC, sensors, and software; organisations responsible for maintenance of transport infrastructure, manufacturers of the elements and structures of transport infrastructure, etc.). The analysis of the issue of the security of data transfer also regarded data transfer to third parties.The study also referred to the issues of adaptation of adjacent industries involved to the process of AC implementation, as well as to the ethical issues in the process of decision-making by AC software in a critical situation. The formulated recommendations on improving the transport infrastructure of the city of St. Petersburg are aimed at solving the problems identified in the article.

A 3D-Printed Capacitive Smart Insole for Plantar Pressure Monitoring.

Gait analysis refers to the systematic study of human locomotion and finds numerous applications in the fields of clinical monitoring, rehabilitation, sports science and robotics. Wearable sensors for real-time gait monitoring have emerged as an attractive alternative to the traditional clinical-based techniques, owing to their low cost and portability. In addition, 3D printing technology has recently drawn increased interest for the manufacturing of sensors, considering the advantages of diminished fabrication cost and time. In this study, we report the development of a 3D-printed capacitive smart insole for the measurement of plantar pressure. Initially, a novel 3D-printed capacitive pressure sensor was fabricated and its sensing performance was evaluated. The sensor exhibited a sensitivity of 1.19 MPa-1, a wide working pressure range (<872.4 kPa), excellent stability and durability (at least 2.280 cycles), great linearity (R2=0.993), fast response/recovery time (142-160 ms), low hysteresis (DH<10%) and the ability to support a broad spectrum of gait speeds (30-70 steps/min). Subsequently, 16 pressure sensors were integrated into a 3D-printed smart insole that was successfully applied for dynamic plantar pressure mapping and proven able to distinguish the various gait phases. We consider that the smart insole presented here is a simple, easy to manufacture and cost-effective solution with the potential for real-world applications.

Design and manufacturing of a surface plasmon resonance sensor based on inkjet 3D printing for simultaneous measurements of refractive index and temperature

Design and manufacturing of a surface plasmon resonance sensor based on inkjet 3D printing for simultaneous measurements of refractive index and temperature

Self-Powered Gradient Hydrogel Sensor with the Temperature-Triggered Reversible Adhension

The skin, as the largest organ of human body, can use ions as information carriers to convert multiple external stimuli into biological potential signals. So far, artificial skin that can imitate the functionality of human skin has been extensively investigated. However, the demand for additional power, non-reusability and serious damage to the skin greatly limits applications. Here, we have developed a self-powered gradient hydrogel which has high temperature-triggered adhesion and room temperature-triggered easy separation characteristics. The self-powered gradient hydrogels are polymerized using 2-(dimethylamino) ethyl metharcylate (DMAEMA) and N-isopropylacrylamide (NIPAM) under unilateral UV irradiation. The prepared hydrogels achieve good adhesion at high temperature and detachment at a low temperature. In addition, according to the thickness-dependent potential of the gradient hydrogel, the hydrogels can also sense pressure changes. This strategy can inspire the design and manufacture of self-powered gradient hydrogel sensors, contributing to the development of complex intelligent artificial skin sensing systems in the future.

The gas sensing and adsorption properties of XO2 (X = Ti, Zr, Hf) doped C3N towards H2S, SO2, SOF2: A first-principles study

In this paper, XO 2 (X = Ti, Zr, Hf) doped C 3 N nanosheet is firstly proposed to detect SF 6 decomposition products: H 2 S, SO 2 , and SOF 2 . The electronic properties and adsorption mechanisms of XO 2 (X = Ti, Zr, Hf) doped C 3 N nanosheet towards H 2 S, SO 2 , SOF 2 are systematically explored. Metal oxide particles doping effectively modulate the band gap, with the decline of 27.8 %, 22.3 % and 42.6 % in TiO 2 , ZrO 2 and HfO 2 doped systems, furthermore, dopants provide abundant active sites for gas adsorption and enhance electron mobility and electrical conductivity of the pristine C 3 N surface. TiO 2 -C 3 N holds the best adsorption performance among three doping systems, in which the E ads reach up to −1.158 eV, −2.238 eV, −1.574 eV in H 2 S, SO 2 and SOF 2 systems. The τ of H 2 S, SO 2 , SOF 2 escape from TiO 2 -C 3 N surface are 3.7 × 10 7 s, 4.8 × 10 14 s, 6.88 × 10 25 s. Improved adsorption energy of TiO 2 -C 3 N is twice than that of pristine C 3 N nanosheet's. ZrO 2 , HfO 2 -C 3 N have semblable adsorption capacity to target gases. In SO 2 and SOF 2 adsorption of HfO 2 doped systems, SO 2 and SOF 2 obtained the charges of 0.303 e and 0.189 e respectively. The results provide a theoretical basis for further manufacture of industrial hazardous gas sensors and online monitoring of SF 6 insulated equipment. • XO 2 (X=Ti, Zr, Hf) nanoparticle modification is firstly proposed to improve C 3 N’s surface electronic properties. • Transition metal oxides doped C 3 N exhibits ideal adsorption and scavenging properties for H 2 S, SO 2 , and SOF 2 . • The results provide a theoretical basis for further manufacture of industrial hazardous gas sensors and online monitoring of SF 6 insulated equipment.

Direct ink write 3D printing of wave propagation sensor

The ability to detect impact waves and their propagation across materials is the key to structural health monitoring and defect detection of materials. To detect impact waves from a certain type of structures, it is important for a sensor to be highly flexible and complex in shape. Direct ink write (DIW) allows for the manufacturing of complex sensors. This article presents the fabrication of a flexible impact wave propagation sensor (IWPS) through the DIW technique. The dispersion of a ferroelectric ceramic material barium titanate (BaTiO3, or BTO) in polydimethylsiloxane (PDMS), not only enhances the flexibility of the 3D (three-dimensional) printed sensor but also ensures the uniform piezoelectric response throughout the whole sensor. This research explored the impact load generated impact wave in the flexible sensor and sensing response. The capability of DIW for multi-material printing was utilized to print multi-walled carbon nanotube based electrodes on BTO/PDMS stretchable composites. A total of 50 wt% of BTO in the PDMS matrix resulted in a piezoelectric coefficient of 20 pC N−1 after contact poling of IWPS. Upon applying impact loading at the center of the sensor, an impact wave was generated which gradually diminished with the distance from the origin of the applied impact load. The impact wave propagation was quantitatively characterized by measuring output voltage from different nodes of IWPS. Additionally, from the voltage response time difference at different locations of the sensor, the particle-wave velocity of a certain material attached to IWPS was determined in this research. Using the custom-designed IWPS, it was found that the particle-wave velocity of stainless steel and low-density polyethylene were 5625 m s−1 and 2000 m s−1 respectively, which are consistent with their theoretical values.

A Flexible Capacitance Strain Sensor with Stitched Contact Terminals

AbstractFlexible strain sensing in wearables and textiles, employs simple resistive sensor elements which suffer from high hysteresis. Textile compatible capacitive strain sensors that have low hysteresis and negligible cross‐axis sensitivity will be ideal for sensing human movement and shape change. In this work, a non‐MEMS based flexible interdigital capacitive strain sensor is proposed. The proffered sensor is built using flexible elastomer material with stitched conductive threads serving as internal and external contacts thereby making the sensor easily customizable. The developed sensor is amenable for fabrication using large scale textile sensor manufacturing techniques. The low sensitivity due to the low dielectric constant of most elastomers is addressed by employing high dielectric constant additives while molding the elastomer sections. The developed sensor is virtually insensitive to cross‐axis strain by design and is capable of withstanding stretching up to 160%. The prototype sensor built and tested has a sensitivity of and portrays a worst‐case nonlinearity error of <±2.9%. An application, where the developed sensor was stitched on to a glove to sense finger movement is presented and discussed. The proposed fully stitch‐able sensors have the versatility to perform fabric‐based wearable strain sensing for body shape and movement analysis.

Hybrid additive manufacturing of a piezopolymer-based inertial sensor

In the last few years, additive manufacturing has been investigated as a promising production methodology in the field of electro-mechanical devices thanks to the high process flexibility, the improved product customizability and the tridimensionality of the fabricated mechanical structures. Electro-mechanical devices are characterized by a dual nature, which combine mechanically moveable parts with electric components. For this reason, their production is particularly advantageous when different additive manufacturing technologies are employed in synergy. In this context, the present work aims at producing and experimentally verify the first functional accelerometer capable of piezoelectric signal readout fully fabricated through additive manufacturing techniques. A smart combination of 3D printing and inkjet materials deposition is here proposed: stereolithography of a photocurable resin is chosen to fabricate the structural components of the accelerometer, while inkjet printing is employed to pattern a P(VDF-TrFE) piezoelectric layer and the corresponding silver electrodes exploited for acceleration readout. The results achieved demonstrate that the proposed hybrid additive manufacturing technology is a very promising route for electro-mechanical sensors fabrication at the mesoscale. • The first fully additively manufactured piezoelectric accelerometer is described. • A hybrid production route that combines 3D printing and inkjet deposition is used. • Stereolithography is used to fabricated the structural part of the accelerometer. • Inkjet deposition is used to pattern a piezoelectric sensing gauge on the sensor. • The finished sensor shows capability to sense accelerations in the 0–10 g range.

Fabrication of Porous Silicon as a Gas Sensor: The Role of Porous Silicon Surface Morphology

Manufacture of an environmental polluting gas sensor with improved properties by controlling the preparation conditions of the photo-electrochemical etching technique (PECE). The amount of porosity, the diameter of the pores, and the thickness of the prepared layer of porous silicon (Psi) can be controlled by changing one or all of these conditions. In this paper, n-type Si with a crystalline orientation (100) was used, whereby PSi was prepared with the use of a red diode laser with a wavelength of 650 nm, using different radiation intensity, and with the constancy of etching time and current density. Through the results obtained, it was noted that: the porosity increases significantly up to 75% as well as the thickness of the PSi layer up to 1.45 µm with the increase in the intensity of the laser beam. Also, examining the morphology of the surface samples by field emission scanning electron microscope (FE-SEM) besides, the average pore diameters of the prepared samples were calculated. It is clear that the intensity of the laser beam used in the irradiation process is one of the important factors in determining the properties of the prepared PSi. PSi samples have been tested by FTIR to investigate chemical bonds on surfaces such as, (Si-Si, Si-H, Si-H2, Si-O-Si, Si-O-Si, Si-H, Si-O-Si). Samples tested as gas sensors and noticed that an increase in the sensing current to 5.3 µA has appeared with the increase of porosity value where methanol gas is used as background.

Additive manufacturing for capacitive liquid level sensors

A new manufacturing wave concerning the Additive Manufacturing of sensors is spreading: several benefits, such as cost, time, and manual task reduction, can be achieved. The aim of the present research is the one-shot Additive Manufacturing of a low-cost capacitive sensor for liquid level sensing. The Material extrusion (MeX) technology was used to fabricate the proposed sensors (composed of a flexible substrate, two conductive electrodes, and a top flexible coverage), and a Design for Additive Manufacturing (DfAM) approach in conjunction with the 3D printing force analysis was performed. Very thin conductive tracks (0.5 mm) were manufactured to obtain a sensor having a final capacitance value of 125 pF, readable by common laboratory instrumentation. The sensor has been tested for the liquid level sensing using two different liquids, i.e., sunflower oil and distilled water, exhibiting very good sensitivity of 0.078 frac{pF}{mm} and 0.79 frac{pF}{mm}, respectively, with high repeatability, thus obtaining sensing performances comparable with that of more expensive sensors found in literature. Moreover, the proposed sensor showed high linearity (R2 ≥ 0.997), which resulted in a maximum propagated level error of 1.4 mm. The present research proves that the inexpensive MeX technology can be successfully employed for the fabrication of high-performance capacitive sensors: the sensor manufacturing cost (related to raw materials) is 0.38 €, and no manual assembly tasks were performed. This study lays the foundation for the one-shot fabrication of smart structures with capacitive sensors on board, saving manufacturing time and cost.

Fabrication of a Conductive Pattern on a Photo-Polymerized Structure Using Direct Laser Sintering

Three-dimensional (3D)-printed electronic technology is considered to have great potential as it can be utilized to make electronic products with complex 3D shapes. In this study, based on a 3D printer with single UV laser equipment, we continuously performed photo-polymerization (PP) and selective metal powder sintering to fabricate a conductive pattern. For this, 3D structures were printed at a low energy using a 355 nm DPSS laser with a galvanometer scanner, which are widely used in PP-type 3D printing, and then the selective sintering of metal powders was performed with a high energy. In order to obtain a high-conductivity pattern by laser sintering, a circuit pattern that could actually be operated was fabricated by experimenting with various condition changes from mixing the metal composite resin to the laser process. As a result, it was found that the optimal result was to irradiate a 0.8 W UV laser with a beam spot size of 50 µm to 50 vol% aluminum composite resin. At this time, an optimal conductive pattern with a resistance of 0.33 Ω∙cm−1 was obtained by setting the pulse repetition rate, scan path interval, and scanning speed to 90 kHz, 10 μm, and 50 mm/s, respectively. This suggested process may be of great help in the manufacturing of practical 3D sensors or functional products in the future.