Film Sensor Research Articles

Z-Freq Hybrid: Signal Analysis Based Car Air Conditioning Compressor Monitoring Technique Using Accelerometer and Piezo-Film Sensor

The efficiency and performance of car air conditioning systems rely heavily on adequately functioning the compressor and its associated components. There are many ways to detect an unfunctioning compressor and one of them is through vibration. Disfunctioning compressors could lead to discomfort, fatigue, stress and fogging windows, especially in long-distance driving. Thus, researchers focus on detecting the nonfunctioning car air conditioning compressor early. This paper introduced a new enhanced statistical method, namely Z-freq Hybrid. Z-freq Hybrid was based on a Z-notch frequency domain filter with a combination input of two different types of sensors introduced to detect functioning compressors. Data were recorded at various compressor speeds using an accelerometer and piezo film sensor with Signal Express 2015 software. The acceleration (m/s2) and voltage (mV) data were analyzed to find the combination degree of scattering data in a Z-freq Hybrid chart. The analyzed data show that the Z-freq Hybrid coefficient increases as the compressor’s speed increases. Then, the value dropped significantly when the compressor was dysfunctional. In conclusion, a Z-freq Hybrid can be employed to detect abnormalities and irregular vibration patterns, which may indicate the impending failure of a compressor.

Mechanical behavior monitoring of composite hybrid bonded‐riveted joints using high‐stability MXene sensors

AbstractComposite adhesive rivet hybrid connection structure has been more and more recognized and applied in aerospace, automobile, and other industries due to its high strength, corrosion resistance, and good stability. However, due to the particularity of the composite structure and the complex nonlinear coupling factors existing in the bearing process of the adhesive rivet hybrid connection structure, it is difficult to carry out structural health monitoring of the composite adhesive rivet hybrid connection structure. In this paper, a new fabrication technique is proposed to fabricate MXene thin film sensors with excellent performance. The MXene sensor can be tailored to the required size and arrangement to monitor the hybrid connection structure. The multi‐stage loading‐unloading test verifies the feasibility of using the MXene sensor to monitor the hybrid connection structure. The monitoring curves of the MXene sensor for composite adhesive rivet mixed connection structure specimens under low‐speed impact test and vibration fatigue test were obtained, and the sensing mechanism of the MXene sensor was explained. The proposed monitoring method based on the MXene sensor is suitable for the health monitoring of adhesive rivet hybrid connection structures under tensile‐compression, impact, and vibration conditions.Highlights MXene sensors can be integrated into composite hybrid bonded‐riveted joints without defects. MXene sensors combined with flexible circuits can form a high‐stability monitoring array. Monitor the mechanical behavior of bonded and riveted areas by the resistance change rate of MXene sensors. Real‐time monitor the micro damage and acceleration changes under the vibration environments.

Impact detection method based on the ratio of mechanoluminescence intensity

This paper proposes an impact detection method based on the ratio of mechanoluminescence (ML) intensity, as an improvement over traditional methods that rely on absolute ML intensity. The study utilized two types of ML materials, ZnS:Cu2+ and ZnS:Mn2+, which were physically mixed and embedded them in polydimethylsiloxane (PDMS) to fabricate a flexible film sensor. A drop ball experimental setup was constructed, and the ML spectrum of the film sensor under the impact of a small ball was collected through a spectrometer. This established the relationship between impact velocity and the ratio of ML intensities. Experiments proved that the distance of spectral collection has a minimal effect on the measurement results of this method. Compared to traditional methods based on absolute ML intensity, this method has stronger resistance to environmental interference and better applicability. This new impact detection method based on the ratio of ML intensities has broad application prospects in future engineering applications, safety assessments, and material testing.

Investigating Transducer–Tissue Interface Pressure for Soft Tissue Stress–Strain Behavior and the Effects on Echoic Intensities in Ultrasound Imaging of Periodontium

AbstractDiagnostic ultrasound (US) is a major imaging modality to visualize soft tissues and blood flow with the advantages of real‐time imaging, high acceptability to patients, and absence of ionizing radiation. US imaging provides important clinical measurements, e.g., thickness of gingiva for treatment planning in orthodontics, periodontics, and implantology; or thickness of subcutaneous adipose for optimizing insulin injection. However, the image quality and measurements of anatomical structures can be inconsistent, i.e., due to varying pressure exerted by an US transducer. Herein, a simple device is developed to real‐time measure the interface pressure applied on tissues by the US transducer. A thin‐film piezo‐resistive sensor with a small footprint is integrated to sense the pressure. A theoretical model, based on hyperelastic material behavior, is verified using the pressure measured by the thin film sensor and the thickness determined on ultrasonograms. The device is also tested on porcine samples in the pressure range of 50–300 kPa for imaging gingiva boundaries, identifying tissue thickness, and probing tissue biomenchanical properties. The device enables the understanding on the optimal range of applied pressure for higher contrast imaging. The information of the on‐tissue pressure and the tissue deformation determined on the US images help to derive the biomechanical stress–strain behavior of the tissues.

Self‐Powered Underwater Pressing and Position Sensing and Autonomous Object Grasping with a Porous Thermoplastic Polyurethane Film Sensor

AbstractMost flexible ionic tactile sensors can hardly be used in deep sea due to their poor antiswelling and anticompression properties under high hydrostatic pressure. To achieve pressure and position sensing under high hydrostatic pressure, a self‐powered underwater tactile sensor made of a porous thermoplastic polyurethane (TPU) film is presented in this paper. The sensor works by generating an electric current due to the different moving velocities of ions in the porous film under pressing. Experimental results show that the magnitude of the generated current signal increases with the applied pressure, the contacting area, and ion concentration of the solution. The direction and magnitude of the current signal depend on the pressing position of the film. The signal magnitude decreased with the closer to the center of the film. The maximum pressure sensitivity and positioning resolution are 0.62 kPa−1 and 1.31 mm respectively. Response time (0.19 s), 0.67 s recovery time, and 50–600 kPa pressure detection range are achieved. In addition, the signal magnitude is decreased only by 15.53% when the sensor is placed underwater at a simulated depth of 100 m. Proof of concept demonstration of underwater autonomously grasping objects of different weights with this sensor is successfully achieved.

Conjugated Polymer-Based Hydrogel Film for a Fast and Sensitive Detection of Fe(Ⅲ) in Vegetables.

Fluorescent film sensors are ideal for the real-time outdoor detection of heavy metal ions of Fe3+, but they are limited because of their low sensitivity and long response time due to their special structure. In this work, we constructed a fluorescent hydrogel for the specific detection of Fe3+, utilizing poly(9-fluorenecarboxylic acid) (PFCA) as the sensing moiety and sodium alginate (SA) as the cross-linking substrate, which exhibited a rapid and selective recognition of Fe3+ among a panel of 16 anions and 21 cations. It can sense Fe3+ at 0.1 nM immediately owing to the porous network structure of the PFCA-SA film that provided enhanced ion transport channels and active sites, and the "molecular line effect" of polymer PFCA. Moreover, we successfully applied this platform to detect Fe3+ in four different vegetable samples. This work provides an innovative and effective strategy for fabricating green and sustainable fluorescent sensors.

Quercetin nanoparticles decorated on Arabic gum and polyvinyl alcohol composite as a film sensor for fluorescence detection of meropenem

Moving towards green chemistry to minimize the diverse effect of chemicals on human health and environment has become a great issue in chemistry. On the other hand, determination of pharmaceuticals is an important issue for both human health and environment. In this regard two natural and benign compounds such as quercetin a polyphenolic flavonoid and Arabic Gum (AG) a polysaccharide were used to construct a sensor for meropenem. Herein, a new method was established for the synthesis of AG and polyvinyl alcohol (PVA) composite decorated by quercetin nanoparticles (QUENPs) as a fluorimetric film sensor to measure meropenem. In order to embed QUENPs in the polymer composite substrate, first QUENPs were synthesized and then added to the prepared composite solution under optimal conditions. The characteristics of AG and PVA composite (AG-PVA) and AG-PVA composite decorated by QUENPs films (QUENPs-AG-PVA), before and after the addition of meropenem was studied by TEM, FT-IR and EDX-Mapping. The developed film sensor was placed in a holder made with 3D printer. The difference in the fluorescence intensity of the fabricated film before and after the addition of meropenem was taken as the signal for measuring meropenem. The effect of different parameters on the fabrication of film fluorimetric sensor such as the concentration of polymer solutions, the volume of QUENPs and the volume of glycerol were investigated. Factors affecting the measurement of meropenem such as pH, type of buffer, volume of meropenem solution added on the sensor and time were also investigated. Under the obtained optimum conditions, the calibration graph was linear in the concentration range of 50–800 ng mL−1 with a correlation coefficient (r) of 0.9976 and the detection limit was 42.6 ng mL−1. The relative standard deviation was 3.5% and 1.4%, for eight replicate determinations of 100 ng mL−1 and 400 ng mL−1 of meropenem, respectively. The proposed method was successfully utilized for determination of meropenem in blood serum, human urine and pharmaceutical samples.

High Signal to Noise Ratio Piezoelectric Thin Film Sensor Based on Elastomer Amplification for Ambulatory Blood Pressure Monitoring.

Continuous pulse wave detection can be used for monitoring and diagnosing cardiovascular diseases, and research on pulse sensing based on piezoelectric thin films is one of the hot spots. Usually, piezoelectric thin films do not come into direct contact with the skin and need to be connected through a layer of an elastic medium. Most views think that the main function of this layer of elastic medium is to increase the adhesion between the sensor component and the skin, but there is little discussion about the impact of the elastic medium on pulse vibration transmission. Here, we conducted a detailed study on the effects of Young's modulus and the thickness of elastic media on pulse sensing signals. The results show that the waveform amplitude of the piezoelectric sensing signal decreases with the increase of Young's modulus and thickness of the elastic medium. Then, we constructed a theoretical model of the influence of elastic media on pulse wave propagation. The amplitude of the pulse wave signal detected by the optimized sensor was increased to 480%. Our research shows that by regulating Young's modulus and thickness of elastic media, pulse wave signals can undergo a similar amplification effect, which has an important theoretical reference value for achieving ambulatory blood pressure monitoring based on high-quality pulse waves.

Heat transfer enhancement of water flow over a heating flat plate using 20 kHz ultrasonic waves irradiated from submerged horn-type transducer

The enhancement of heat transfer of water flow over a flat plate under 20 kHz ultrasound irradiated from a submerged horn-type transducer was investigated experimentally in a water tunnel. To examine the ultrasonic effects, the transducer emitted waves perpendicular to the mainstream direction, and the freestream velocity varied between 0.12 and 0.17 m/s. The transducer position was fixed at 0.45 m from the plate leading edge in a streamwise direction. This position was altered in a heightwise direction as dimensionless heightwise distances (Z) that were divided by the diameter of the horn-tip transducer (12 mm) at 1.5, 3.0, and 4.5 from the plate surface. A hot film sensor and thermochromic liquid crystals coated on the test surface were used to demonstrate the hydrodynamic and thermal characteristics, respectively. The maximum temperature reduction of 3.5 °C was observed in the case of Z = 1.5. By employing a horn-type transducer, the acoustic jet and cavitation phenomena played a key role in destabilizing the thermal and velocity boundary layers, which resulted in a decrease in surface temperature. The incident wave shape was triangular, with an enlarging lateral zone along the flow stream. When the waves were released at Z = 1.5, the local Nusselt number was increased up to 2.55 compared to without waves. Under ultrasonic effects, the near-wall flow velocity was detected to be decreasing upstream prior to the incident zone while increasing in the incident region. When waves existed, the highest turbulent intensity was up to 29 times more intense than it was in the absence of waves. Furthermore, a predictive formula for the Nusselt number with ultrasound was established depending on the local Reynolds number and the distance between the ultrasonic source and test surface.

Large-area, size-controlled and transferable graphene oxide-metal films for humidity sensor

The lack of low-cost methods to synthesize large-area graphene-based materials is still an important factor that limits the practical application of graphene devices. Herein, we present a facile method for producing large-area graphene oxide-metal (GO–M) films, which are size controllable and transferable. The sensor constructed using the GO–M film exhibited humidity sensitivity while being unaffected by pressure. The relationship between the sensor’s resistance and relative humidity followed an exponential trend. The GO–Mg sensor was the most sensitive among all the tested sensors. The facile synthesis of GO–M films will accelerate the widespread utilization of graphene-based materials.

Deep Learning Enabled SERS Identification of Gaseous Molecules on Flexible Plasmonic MOF Nanowire Films.

Through the capture of a target molecule at the metal surface with a highly confined electromagnetic field induced by surface plasmon, surface enhanced Raman spectroscopy (SERS) emerges as a spectral analysis technology with high sensitivity. However, accurate SERS identification of a gaseous molecule with low density and high velocity is still a challenge due to its difficulty in capture. In this work, a flexible paper-based plasmonic metal-organic framework (MOF) film consisting of Ag nanowires@ZIF-8 (AgNWs@ZIF-8) is fabricated for SERS detection of gaseous molecules. Benefiting from its micronanopores generated by the nanowire network and ZIF-8 shell, the effective capture of the gaseous molecule is achieved, and its SERS spectrum is obtained in this paper-based flexible plasmonic MOF nanowire film. With optimal structure parameters, spectra of gaseous 4-aminothiophenol, 4-mercaptophenol, and dithiohydroquinone demonstrate that this film has good SERS performance, which could maintain obvious Raman signals within 30 days during reproducible detection. To realize SERS identification of gaseous molecules, deep learning is performed based on the SERS spectra of the mixed gaseous analyte obtained in this flexible porous film. The results point out that an artificial neural network algorithm could identify gaseous aldehydes (gaseous biomarker of colorectal cancer) in simulated exhaled breath with high accuracy at 93.7%. The integration of the flexible paper-based film sensors with deep learning offers a promising new approach for noninvasive colorectal cancer screening. Our work explores SERS applications in gaseous analyte detection and has broad potential in clinical medicine, food safety, environmental monitoring, etc.

Laser-Structured Thin Film Sensor Technology for Sliding Bearings in Internal Combustion Engines

Abstract Global issues such as climate change, environmental pollution, and conservation of resources require manufacturers of internal combustion engines (ICE) to achieve substantially reduced emissions of greenhouse gases and pollutants as well as increased engine efficiency and durability. Condition monitoring and predictive maintenance approaches for sliding bearings in ICEs are key tools for increasing engine durability and saving resources by exploiting more of the useful lifetime of a bearing while avoiding critical engine operation caused by bearing wear and failure. These approaches require appropriate measurement technology capable of acquiring informative parameters that reflect the current condition of the bearings while withstanding the high temperatures and mechanical loads encountered inside the engine and accommodating spatial constraints. This paper deals with research work related to advanced sensor technology that is highly integrated into sliding bearings so that information is obtained nearly directly from relevant areas such as the bearing running layer and the lubrication gap. An isolated, sputtered sensor layer with a thickness of a few micrometers is employed in combination with a laser structuring process to form the desired thin film sensor structure below the bearing running surface. While several measurement parameters and corresponding sensor types are conceivable, this paper focuses on temperature and strain measurements that rely on a change in the electrical resistance of the sensor layer material. Promising sensor layouts and positions targeted for use in condition monitoring applications in ICEs are elaborated in detail. Developments and challenges in implementing the sensor technology concept—in particular with regard to the process of manufacturing the sensor as well as the wire contacting—are outlined in depth. The paper concludes by presenting measurement results obtained with this sensor technology at lab scale as well as an outlook toward implementing the instrumented bearings in ICEs.

A Nanofilm-Based Fluorescent Sensor toward Highly Efficient Detection of Ethephon.

Ethephon (ETH) is widely used to promote fruit ripening and improve fruit quality. However, improper use is harmful to human health and to the environmental safety. Therefore, development of the techniques for on-site and at real-time monitoring of ETH is of importance for its safe use. In this work, we developed a nanofilm-based fluorescence film sensor (FFS) and realized highly efficient detection of ETH in vapor phase, where the detection limit (DL) is <0.2 ppb, the response time is less than 10 s, and the interference is almost free. The unusual sensing performance of the sensor was ascribed to the specific binding of the nanofilm to ETH and to its great porosity, which enables efficient adlayer mass transfer, a requirement for high signal-to-noise ratio. Moreover, visualization-based qualitative sensing is also realized. The nanofilm, a key component of the sensor, was prepared at the humid air/DMSO interface. The building blocks used were a specially designed fluorescent o-carborane derivative (CB-2CHO) and a cross-linker BTN possessing three acylhydrazine groups. The nanofilm as prepared is flexible, uniform, thickness tunable, and photochemically super stable. We believe our effort not only addresses the challenging issue of on-site and at real-time detection of ETH but also provides another route for developing new FFSs via sensing film innovation.

Thick Film Sensor Manufacturing Techniques for Realization of Smart Components via Low Pressure Die Casting

Recent developments like autonomous driving have increased the interest of the automotive industry in structural health and condition monitoring of safety-relevant components often manufactured via High or Low Pressure Die Casting (HPDC, LPDC). Specifically the latter process is important in this field as the improved quality of castings produced facilitates T6 heat treatments aimed at optimizing mechanical performance of such components. The specific challenge associated with this approach is that it produces critical thermal loads which may compromise the characteristics of the integrated sensor. The present study shows the results obtained by LPDC on thick film sensor systems prepared by means of screen printing on aluminum substrates. The response of the sensor systems to the thermal loads associated with the casting process is evaluated in casting experiments, with temperatures reached during casting checked by means of thermocouples attached to the inserts. The focus is on the influence on general properties of the piezoresistive sensors as well as on their response to thermal and mechanical stimuli. The results show that in contrast to HPDC, in the case of LPDC, the former provides stimuli for thermally induced processes which can compromise sensor layers. The respective trends have been studied via resistance measurements on samples subjected to repeated firing cycles and actual casting experiments.

A Study on the Surface Treatment Process of Surface-resistive ITO Film Sensors

A Study on the Surface Treatment Process of Surface-resistive ITO Film Sensors

Structural and Morphological Characterization of Iridium and Ir/Au Films for Transition Edge Sensors

Superconducting Transition Edge Sensors employed in X-ray astrophysics space missions were realized and fully characterized in the Low temperature detector laboratory at UniGe. Several samples of Ir and Ir/Au bilayer films were grown by pulsed laser deposition at different deposition rate, varying thickness and resulting variability in critical temperature (Tc) was observed. In particular, we noticed two classes of films having discrete critical temperature (Tc), one at about the critical temperature of the bulk Ir and one at around 1.6 times compared to the bulk. Structural characterization was made and interesting correlation between critical temperature (Tc) and deposition conditions were found. Detailed X-Ray Diffraction investigations suggest a possible explanation of this effect with a clear correlation between microstrain value, grain size, and critical temperatures of the films. The study has been carried out to optimize the specified conditions to grow the film under which it is possible to accurately predict the critical temperature (Tc) by analyzing the X-ray diffraction patterns of Ir/Au films.

Preparation of graphene by circulating supercritical CO2 jet cavitation and its application in flexible sensor films

In this paper, a simple operation, mild condition and no chemical intercalation method for graphene nanosheets (GNs) exfoliating was proposed. By utilizing the zero surface tension of supercritical carbon dioxide (scCO2) and the stable cavitation field generated by cavitation devices, the growth and rupture of cavitation bubbles between graphene layers were induced. The highest concentration of graphene dispersion was 0.723 mg/mL, with about 90% of GNs within 5 layers and about 36.6% of GNs having lateral dimensions greater than 1 μm, at an intensity ratio of ID/IG of 0.26. The tensile strength of the graphene-TPU composite film reaches 105.9 MPa, and the thermal conductivity can be adjusted by centrifugation speed to meet different requirements, with a maximum value of 20.8 W/(m∙K) at room temperature. In addition, the test results in cyclic stretching and temperature cycling experiments showed good repeatability, with a maximum sensitivity coefficient (GF) of 17.5. It has been proven that flexible graphene film can respond stably and quickly to input information, and convert it into strong signals for processing, making it an ideal material for pressure and temperature sensors.

Non-contact, highly sensitive sugar concentration detection based on Co3Sn2S2 Weyl semimetal thin film sensor by terahertz wave.

Blood sugar is an important biomedical parameter of diabetic patients. The current blood sugar testing is based on an invasive method, which is not very friendly for patients who require long-term monitoring, while the non-invasive method is still in the developing stage. In this paper, we design a non-invasive and highly sensitive terahertz wave detector with Co3Sn2S2 semimetal thin film to test sugar concentration. As different concentrations have inconsistent responses to terahertz wave, we can deduce the concentration of the sugar solution to realize real-time highly sensitive detection of blood sugar concentration. This novel method can be further expanded to 6 G edge intelligence for non-invasive and real-time monitoring of blood sugar, and promote the development of 6 G technology.

A biomimetic nociceptor system with tactile perception based on Ni-Al layered double hydroxides/gelatin heterojunction memristor

The sensations of touch and pain are fundamental components of our daily existence, serving as conduits for providing crucial insights into our environment and ensuring the safeguarding of our health. To date, the exploration of artificial systems that combine pain and touch perception has remained very limited. Moreover, memristor based visualization of pain degree is rarely reported. The electronic simulation of the from pressure stimuli to nociceptors was conducted in this work. For this purpose, a bionic sensory system has been developed to present tactile perception. In this system, the piezoelectric film sensor serves as an electronic skin to mimic artificial mechanoreceptors for sensing external pressure stimulation and generating signals. Meanwhile, the Ni-Al layered double hydroxides (LDHs)/gelatin heterojunction memristor emulates biological nociceptors to receive and process receptor signals, with luminous diode used as displays to indicate the degree of artificial contusion. The Ni-Al LDHs/gelatin heterojunction memristor demonstrates essential characteristics of nociceptors, including threshold, no adaptation, relaxation, and sensitization phenomena of allodynia and hyperalgesia. This biomimetic artificial tactile and pain perception system successfully simulates the perception threshold and sensitivity to pressure stimuli. The potential ability of humanoid robots could be demonstrated by utilizing the system as an artificial tactile alarm system.

Poly(vinyl chloride)/Nanocarbon Composites for Advanced Potentiometric Membrane Sensor Design.

Polymer nanocomposites filled with carbon nanoparticles (CNPs) are a hot topic in materials science. This article discusses the current research on the use of these materials as interfacial electron transfer films for solid contact potentiometric membrane sensors (SC-PMSs). The results of a comparative study of plasticized poly (vinyl chloride) (pPVC) matrices modified with single-walled carbon nanotubes (SWCNTs), fullerenes-C60, and their hybrid ensemble (SWCNTs-C60) are reported. The morphological characteristics and electrical conductivity of the prepared nanostructured composite films are reported. It was found that the specific electrical conductivity of the pPVC/SWCNTs-C60 polymer film was higher than that of pPVC filled with individual nanocomponents. The effectiveness of this composite material as an electron transfer film in a new potentiometric membrane sensor for detecting phenylpyruvic acid (in anionic form) was demonstrated. Screening for this metabolic product of phenylalanine in body fluids is of significant diagnostic interest in phenylketonuria (dementia), viral hepatitis, and alcoholism. The developed sensor showed a stable and fast Nernstian response for phenylpyruvate ions in aqueous solutions over the wide linear concentration range of 5 × 10-7-1 × 10-3 M, with a detection limit of 10-7.2 M.