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A parallel three-coil wear particle sensor is innovatively proposed with the detachable substrate and magnetic rings. The magnetic rings are designed and fabricated using polydimethylsiloxane (PDMS) and iron-based amorphous soft magnetic material (IASM). The excitation coils surround the magnetic rings, leaving only a 1mm air gap on the inner side (near the flow channel). The magnetic rings are magnetized under the action of the high-frequency alternating magnetic field, which forms an enhanced magnetic field with a high gradient distribution in the detection area. Through numerical simulation and experimental verification, the influence of IASM concentration, radial position and size of wear particles on the sensor output signal are studied. With the increase of IASM concentration, the sensor detection sensitivity rises dramatically. The sensor with 75% IASM magnetic rings can effectively detect 60 $\mu \text{m}$ iron particles and 160 $\mu \text{m}$ copper particles in a 10mm flow channel; the detection error rate is less than 15% in the actual lubrication circuit, which fully meets the needs of early abnormal wear fault diagnosis of mechanical equipment. Therefore, this method is a promising candidate for developing the large-flow electromagnetic wear particle sensor sensitivity. [ABSTRACT FROM AUTHOR]

Accurate measurement and monitoring of respiration is vital in patients affected by severe acute respiratory syndrome coronavirus – 2 (SARS-CoV-2). Patients with severe chronic diseases and pneumonia need continuous respiration monitoring and oxygenation support. Existing respiratory sensing techniques require direct contact with the human body along with expensive and heavy Holter monitors for continuous real-time monitoring. In this work, we propose a low-cost, non-invasive and reliable paper-based wearable screen printed sensor for human respiration monitoring as an effective alternative of existing sensing systems. The proposed sensor was fabricated using traditional screen printing of multi-walled carbon nanotubes (MWCNTs) and polydimethylsiloxane (PDMS) composite based interdigitated electrodes on paper substrate. The paper substrate was used as humidity sensing material of the sensor. The hygroscopic nature of paper during inhalation and exhalation causes a change in dielectric constant, which in turn changes the capacitance of the sensor. The composite interdigitated electrode configuration exhibited better response times with a rise time of 1.178s being recorded during exhalation and fall time of 0.88s during inhalation periods. The respiration rate of sensor was successfully examined under various breathing conditions such as normal breathing, deep breathing, workout, oral breathing, nasal breathing, fast breathing and slow breathing by employing it in a wearable mask, a mandatory wearable product during the current COVID-19 pandemic situation.Thus, the above proposed sensor may hold tremendous potential in wearable/flexible healthcare technology with good sensitivity, stability, biodegradability and flexibility at this time of need. [ABSTRACT FROM AUTHOR]

This contribution reports the development and characterization of an optical system based on parallel Fiber Bragg Gratings (FBGs) to monitor the movements of the wrist and fingers of a hand. The system consisted of a reflective configuration made of FBGs detecting the movements of the fingers and one more located on the wrist as a reference. All FBGs were multiplexed in order to collect the basic movements of the hand. Fibers were embedded in polydimethylsiloxane for protection and to give flexibility to the optical detection setup. Measurements of strain, angle and torsion were performed during the experiments, obtaining sensitivities up to 1.29 pm/ $\mu \varepsilon $ in strain and 64.23 pm/° in angle. Also, a study on the influence of a single sensor on the performance of the whole system was analyzed for a complete study of this proof of concept. The obtained results present a simple system that can be used to monitor the positions of the hand or for the rehabilitation of patients suffering from neuromotor or post-stroke diseases. [ABSTRACT FROM AUTHOR]

A novel capacitive pressure sensor based on micro-structured polydimethylsiloxane (PDMS) dielectric layer was developed for wearable E-skin and touch sensing applications. The pressure sensor was fabricated on a flexible polyethylene terephthalate (PET) substrate, using PDMS and silver (Ag) as the dielectric and electrode layers, respectively. A set of PDMS films with pyramid shaped micro-structures were fabricated using a laser engraved acrylic mold. The electrodes (top and bottom) were fabricated by depositing Ag on PET films using additive screen-printing process. The pressure sensor was assembled by attaching the top and bottom Ag electrodes to the smooth side of pyramid shaped micro-structured PDMS (PM-PDMS) films. The top PM-PDMS was then placed on the bottom PM-PDMS. The capability of the fabricated pressure sensor was investigated by subjecting the sensor to pressures ranging from 0 to 10 kPa. A sensitivity of 0.221% Pa $^{\mathbf {-1}}$ , 0.033% Pa $^{\mathbf {-1}}$ and 0.011% Pa $^{\mathbf {-1}}$ along with a correlation coefficient of 0.9536, 0.9586 and 0.9826 was obtained for the pressure sensor in the pressure range of 0 Pa to 100 Pa, 100 Pa to 1000 Pa, and 1 kPa to 10 kPa, respectively. The pressure sensor also possesses a fast response time of 50 ms, low hysteresis of 0.7%, recovery time of 150 ms and excellent cycling stability over 1000 cycles. The results demonstrated the efficient detection of pressure generated from various activities such as hand gesture and carotid pulse measurement. The PM-PDMS based pressure sensor offers a simple and cost-effective approach to monitor pressure in E-skin applications. [ABSTRACT FROM AUTHOR]

A novel flexible pressure sensor, based on polydimethylsiloxane (PDMS) and eutectic gallium–indium (EGaIn) liquid metal, was developed for detecting various applied pressures. The sensor was fabricated with PDMS polymer-based electrode channels that are filled with EGaIn liquid metal. The liquid metal-based electrodes were designed to form four capacitors (C1, C2, C3, and C4). Conventional printed circuit board technology was used to manufacture the master mold to form the PDMS-based electrode channels. Corona discharge treatment was employed to bond the PDMS layers at room temperature, under atmospheric pressure. The capability of the fabricated pressure sensor was demonstrated by investigating the capacitive-based response of the device for varying applied pressures. Average capacitance changes ranging from 2.3% to 12.0%, 2.6% to 11.8%, 2.5% to 12.2%, and 2.7% to 13.1% when compared with the based capacitance of 14.1, 15.1, 13.8, and 13.3 pF were obtained for C1, C2, C3, and C4, respectively, for applied pressures ranging from 0.25 to 1.10 MPa. A linear relationship was obtained for the average capacitance change with a sensitivity of 0.11%/MPa and a correlation coefficient of 0.9975. The results obtained thus demonstrate the feasibility of employing liquid metal-based electrodes for the fabrication of flexible pressure sensing devices. [ABSTRACT FROM AUTHOR]

A novel capacitive sensor, which can detect 2-Furfuraldehyde (2-FAL, C5H4O2, in ppm order) in transformer oil, is developed. No such sensor is reported earlier in the literature. The 2-FAL is released in transformer oil with the ageing of the transformer and is a promising indicator for remaining useful life of the solid insulation. The sensor is fabricated by coating a molecularly imprinted polymer (MIP) made from polydimethylsiloxane (PDMS) on a copper electrode. The MIP coating has the template of 2-FAL molecules. On testing, the 2-FAL molecules in transformer oil are adsorbed on the templates, which results in a change in capacitance of the sensor. The sensor is tested in the range of 1–20 ppm for measuring 2-FAL concentration and shows an average sensitivity of 0.084 pF/ppm. The sensors are fabricated in different months (batches), and average capacitance values for different oil sample are presented. The sensor reliability is analysed using statistical analysis and repeatability study that shows repeatable results consistently. [ABSTRACT FROM AUTHOR]

A novel highly sensitive fiber sensor for transverse load and temperature measurement has been fabricated by polydimethylsiloxane (PDMS) packaging an S fiber taper (SFT). The PDMS coating is an effective transverse load and temperature transducer due to its material characteristics, such as low Young’s modulus, high Poisson’s ratio, and large thermooptic coefficient, which can efficiently transfer the lateral force into axial tension on the SFT or convert temperature into refractive index (RI) change around SFT. Because the SFT is highly sensitive to axial strain and surrounding RI, the PDMS-coated SFT will have high sensitivities of transverse load and temperature, which have been experimentally obtained up to −29.03 nm/N and −2.17 nm/°C, respectively. In addition, to solve the problem of cross sensitivity, two-wavelength demodulation method has been proposed for simultaneous measurement of transverse load and temperature. [ABSTRACT FROM PUBLISHER]

This paper describes the realization of a soft, flexible, coil fabricated by means of a liquid metal alloy encased in a biocompatible elastomeric substrate for operation in a telemetry system, primarily for application to biomedical implantable devices. Fluidic conductors are in fact well suited for applications that require significant flexibility as well as conformable and stretchable devices, such as implantable coils for wireless telemetry. A coil with high conductivity, and therefore low losses and high unloaded Q factor, is required to realize an efficient wireless telemetry system. Unfortunately, the conductivity of the liquid metal alloy considered-eutectic gallium indium (EGaIn)-is approximately one order of magnitude lower than gold or copper. The goal of this paper is to demonstrate that despite the lower conductivity of liquid metal alloys, such as EGaIn, compared with materials, such as copper or gold, it is still possible to realize an efficient biomedical telemetry system employing liquid metal coils on the implant side. A wireless telemetry system for an artificial retina to restore partial vision to the blind is used as a testbed for the proposed liquid metal coils. Simulated and measured results show that power transfer efficiency of 43% and 21% are obtained at operating distances between coils of 5 and 12 mm, respectively. Further, liquid metal based coil retains more than 72% of its performance (voltage gain, resonance bandwidth, and power transfer efficiency) when physically deformed over a curved surface, such as the surface of the human eye. This paper demonstrates that liquid metal-based coils for biomedical implant provide an alternative to stiff and uncomfortable traditional coils used in biomedical implants. [ABSTRACT FROM PUBLISHER]

The presence of potentially harmful substances in milk is a concern for consumers. The discovery of recombinant DNA technology allowed the production of large quantities of recombinant bovine somatotropin (rbST), which is allowed to be used to increase milk and meat production in many countries. The use of rbST is controversial because of its potential effects on animal and human health. Use of the existing large instruments for the detection of rbST suffers disadvantages such as the need of large quantities of reagents, increased time of assays and most importantly, the high cost of equipment, etc. In this paper, a novel optical lab-on-a-chip (LOC) is proposed for the detection of a fluorophore-tagged rbST. The advantages of a silica-on-silicon platform for the optical waveguide and polydimethylsiloxane for microfluidics are exploited for the fabrication of a low-cost LOC. The tagging of rbST with two different types of fluorophores, such as FITC and Alexa-647, is carried out and used for detection in the proposed LOC. [ABSTRACT FROM PUBLISHER]

This study shows a novel polydimethylsiloxane (PDMS) nitrite sensor using liquid-core waveguide techniques. A 6 cm straight and Teflon AF 1601S coated PDMS microchannel (600 mum width and depth) replicated from a SU-8 master and sealed with a glass slide with the same coating. This formed a low index of refraction channel in which a high index aqueous solution was flowed. Light generated by a fiber-coupled tungsten halogen lamp propagated by total internal reflection to the end of the channel where the light was detected using a palm-size CCD array spectrometer. The result shows a dramatic difference between channels with and without a Teflon coating. The absorbance response of this sensor varies linearly with concentration and adheres to Beer's law. Moreover, calculations of absorbance using this sensor are in excellent agreement with a commercial spectrometer. This innovative technique provides a potentially low-cost and high efficient approach to fill the inspection technology gap between in situ and laboratory analyses. It is believed that the novel PDMS-based nitrite sensor is expected to give an impact to the aqueous inspection and to create a highly value-added technology in optical test and measurement industry. [ABSTRACT FROM PUBLISHER]

A composite optical bend loss sensor for measuring 3-D forces has been developed. The sensor is composed of two optic fiber meshes which are embedded into a polydimethylsiloxane (PDMS) slab. The sensor consists of an array of optical fibers lying in perpendicular rows and columns sandwiched inside an elastomeric pad. A map of normal and shear stress is constructed based on observed macrobending through the intensity attenuation from physical deformation of two adjacent perpendicular fibers. Due to the new addition of the composite design and acrylic holder, the stability of the present sensor is found to be significantly better than our previously reported microfabricated optical bend loss sensor. In this paper, we will report the results of an optical bend loss simulation using the beam propagation method based on a series of images captured by a CCD camera on the fiber's bending curvatures. The result from the simulation will be compared with the results obtained from the experiment. Other results include vertical force and shear measurements at a single pressure point of the sensor. A force image algorithm is used to map the force distribution detected by the sensor. Here, we will present the results of six different shape patterns and two force magnitudes on each shape using a neural network system. We will also present a radio frequency sensor module, which we developed for the composite optical bend loss sensor for remote sensing. [ABSTRACT FROM PUBLISHER]

Accurate measurement and monitoring of respiration is vital in patients affected by severe acute respiratory syndrome coronavirus - 2 (SARS-CoV-2). Patients with severe chronic diseases and pneumonia need continuous respiration monitoring and oxygenation support. Existing respiratory sensing techniques require direct contact with the human body along with expensive and heavy Holter monitors for continuous real-time monitoring. In this work, we propose a low-cost, non-invasive and reliable paper-based wearable screen printed sensor for human respiration monitoring as an effective alternative of existing sensing systems. The proposed sensor was fabricated using traditional screen printing of multi-walled carbon nanotubes (MWCNTs) and polydimethylsiloxane (PDMS) composite based interdigitated electrodes on paper substrate. The paper substrate was used as humidity sensing material of the sensor. The hygroscopic nature of paper during inhalation and exhalation causes a change in dielectric constant, which in turn changes the capacitance of the sensor. The composite interdigitated electrode configuration exhibited better response times with a rise time of 1.178s being recorded during exhalation and fall time of 0.88s during inhalation periods. The respiration rate of sensor was successfully examined under various breathing conditions such as normal breathing, deep breathing, workout, oral breathing, nasal breathing, fast breathing and slow breathing by employing it in a wearable mask, a mandatory wearable product during the current COVID-19 pandemic situation.Thus, the above proposed sensor may hold tremendous potential in wearable/flexible healthcare technology with good sensitivity, stability, biodegradability and flexibility at this time of need.