Pressure Sensor For Monitoring Research Articles

A self-powered sensor for detecting slip state and pressure of underwater actuators based on triboelectric nanogenerator

In challenging underwater environments, mechanical actuators must conquer diverse hurdles and guarantee meticulous and steadfast command while engaging with delicate and pliant targets. To address these issues, a novel pressure and slip state monitoring sensor (PS-TENG) based on the triboelectric nanogenerator principle was proposed to establish a haptic sensing system for underwater actuators. This sensor can detect pressure at the actuator during gripping and the relative slipping speed between the actuator and the target, allowing for precise control based on feedback signals from the perception system. In this study, we established a theoretical framework connecting pressure and electrical signals, explored material preparation methods and manufacturing steps, conducted performance optimization experiments after producing the prototype. Furthermore, we presented a signal processing technique for the sensor's output. Results demonstrated that the sensor can generate an open-circuit voltage signal of up to 45 V at a maximum operating pressure of 13 N. Moreover, within the operating pressure range, the sensor exhibited high sensitivity, reaching up to 4.5 V/N. By analyzing and processing the sensor signals, the actuator can obtain both pressure and relative slipping speed information simultaneously, essential for addressing complex underwater grasping tasks. Our research indicates that the PS-TENG sensor can serve as a reliable and efficient solution for establishing haptic sensing systems in underwater applications. With its excellent performance, this sensor holds broad potential for use in underwater robotics and electronic devices, thereby facilitating the advent of more versatile and dependable equipment in the days to come.

Liquid dielectric layer-based microfluidic capacitive sensor for wireless pressure monitoring

Liquid dielectric layer-based microfluidic capacitive sensor for wireless pressure monitoring

Enhanced sensing performance of EVA/LDPE/MWCNT piezoresistive foam sensor for long-term pressure monitoring

Conductive polymer composites (CPCs) with piezoresistive properties are smart detecting systems with high sensitivity, fast response, and low energy consumption. To enhance their sensitivity and cope with their high filler content requirements, solid CPCs are normally transformed into blends and foams, which reduces the elastic modulus, enabling larger deformations, wider detection range, and increased sensitivity. However, providing reversible and durable sensing properties remains challenging as it depends on the phase morphology, foam cell structure, and particle dispersion. To this end, we use multi-walled carbon nanotube (MWCNT) as a conductive filler with a high aspect ratio and develop CNT-filled ethylene vinyl acetate/low-density polyethylene (EVA/LDPE) blend foams. We fix the foam structure using chemical foaming and crosslinking agents in a compression molding process. To optimize the piezoresistive behavior, we follow a step-wise tuning approach, studying the blending morphology, the foaming attributes, the particle dispersion and affinity, thereby selecting the most promising formulations for further investigations. The least mechanical and electrical hysteresis is obtained at minimum foam density, which is obtained at a compromised crystallinity and crosslinking density. The higher affinity of MWCNT to EVA and the faster crosslinking of the EVA phase results in uniformly dispersed small cells at EVA-rich formulations and 4 phr MWCNT content. The final foam sensor demonstrates an impressive response and recovery times of less than 200 ms and remarkable durability thanks to the optimized cell morphology and mechanical properties. These findings expand the application of carbon-filled polyolefin foams in pressure monitoring, particularly in wearable sensors for strain and motion sensing.

Patent landscape review of non-invasive medical sensors for continuous monitoring of blood pressure and their validation in critical care practice.

Continuous non-invasive monitoring of blood pressure is one of the main factors in ensuring the safety of the patient's condition in anesthesiology, intensive care, surgery, and other areas of medicine. The purpose of this work was to analyze the current patent situation and identify directions and trends in the application of non-invasive medical sensors for continuous blood pressure monitoring, with a focus on clinical experience in critical care and validation thereof. The research results reflect data collected up to September 30, 2022. Patent databases, Google Scholar, the Lens database, Pubmed, Scopus databases were used to search for patent and clinical information. An analysis of the patent landscape indicates a significant increase in interest in the development of non-invasive devices for continuous blood pressure monitoring and their implementation in medical practice, especially in the last 10 years. The key players in the intellectual property market are the following companies: Cnsystems Medizintechnik; Sotera Wireless INC; Tensys Medical INC; Healthstats Int Pte LTD; Edwards Lifesciences Corp, among others. Systematization of data from validation and clinical studies in critical care practice on patients with various pathological conditions and ages, including children and newborns, revealed that a number of non-invasive medical sensor technologies are quite accurate and comparable to the "gold standard" continuous invasive blood pressure monitoring. They are approved by the FDA for medical applications and certified according to ISO 81060-2, ISO 81060-3, and ISO/TS 81060-5. Unregistered and uncertified medical sensors require further clinical trials. Non-invasive medical sensors for continuous blood pressure monitoring do not replace, but complement, existing methods of regular blood pressure measurement, and it is expected to see more of these technologies broadly implemented in the practice in the near future.

Flexible and Wearable Capacitive Pressure Sensor for Monitoring Heart Parameters

The increase in global average life expectancy over the past century has been largely attributed to medical science developments. In this study, we demonstrate a polymer-based capacitive pressure sensor for measuring heart rate and pulse pressure signal. The fabricated sensor has been characterized to evaluate its performance and to verify its repeatability and precision. It is observed that the sensor works in the range of 0 – 8 kPa pressure range and is suitable for measuring the pulse pressure. This sensor has a high sensitivity of 7.11 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the low-pressure range of 0 to 8 kPa. Further, the sensor demonstrated a considerable amount of repeatability with an error less than 6% in consecutive measurements. Moreover, the sensor demonstrated the use of a wearable, flexible piezo-capacitive pressure sensor for pulse pressure monitoring. The wrist pulse was used as the stimulus for the experimental characterization of the sensor, and health markers related to the measured response were also discussed.

Thin Membranes Based on FBG Sensors for Real-Time Subbandage Pressure Monitoring

This work focuses on the manufacturing and testing of a new device for medical bandage monitoring. Excessive pressure exerted from the compression bandage can block the blood flow of the patient, causing different medical complications to the skin, nerves, and circulatory system. On the contrary, if the pressure applied is low, the therapy is not effective. The utility, therefore, arises from a device capable of quantitatively indicating the correct adjustment of the bandage. The technological demonstrators developed consist of a polyurethane elastomeric shell with a thin composite supporting core. Fiber Bragg grating sensors (FBGSs) embedded within this core permit the detection of the subbandage pressure applied during compression therapy. The two prototypes were applied under arm bandages to evaluate their capability to transmit the applied pressure to the embedded FBGS. We demonstrated the ability to monitor the bandaging action by measuring the level of pressure exerted with the rounds of bandages. Moreover, the thin membranes permit the monitoring of the heartbeat of the patient, giving feedback about blood irrotation. The device developed is, therefore, promising to improve the results of compression therapy.

Soft, flexible pressure sensors for pressure monitoring under large hydrostatic pressure and harsh ocean environments.

Traditional rigid ocean pressure sensors typically require protection from bulky pressure chambers and complex seals to survive the large hydrostatic pressure and harsh ocean environment. Here, we introduce soft, flexible pressure sensors that can eliminate such a need and measure a wide range of hydrostatic pressures (0.1 MPa to 15 MPa) in environments that mimic the ocean, achieving small size, high flexibility, and potentially low power consumption. The sensors are fabricated from lithographically patterned gold thin films (100 nm thick) encapsulated with a soft Parylene C film and tested in a customized pressure vessel under well-controlled pressure and temperature conditions. Using a rectangular pressure sensor as an example, the resistance of the sensor is found to decrease linearly with the increase of the hydrostatic pressure from 0.1 MPa to 15 MPa. Finite element analysis (FEA) reveals the strain distributions in the pressure sensor under hydrostatic pressures of up to 15 MPa. The effect of geometry on sensor performance is also studied, and radially symmetric pressure sensors (like circular and spike-shaped) are shown to have more uniform strain distributions under large hydrostatic pressures and, therefore, have a potentially enhanced pressure measurement range. Pressure sensors of all geometries show high consistency and negligible hysteresis over 15 cyclic tests. In addition, the sensors exhibit excellent flexibility and operate reliably under a hydrostatic pressure of 10 MPa for up to 70 days. The developed soft pressure sensors are promising for integration with many platforms including animal tags, diver equipment, and soft underwater robotics.

MoSe2/PVA-based wearable multi-functional platform for pulse rate monitoring, skin hydration sensor, and human gesture recognition utilizing electrophysiological signals

Multifunctional wearable sensors have gained significant popularity in recent years for point of care diagnosis, tackling the myriad of obstacles faced in coping with health-related issues. However, complex fabrication, lack of biocompatibility, non-reusability, and accuracy limit their widespread use. In this work, we report a clean-room-free fabrication of molybdenum diselenide (MoSe2) interspersed with polyvinyl alcohol (PVA) based multifunctional device for in situ and non-invasive high-fidelity human gesture recognition, pulse rate monitoring, and skin hydration sensing. Detailed morphological characterization studies reveal the formation of a rhombohedral structure for MoSe2 nanoflakes stacked vertically to form a micro flower structure. Group synaptic activity of neurons results in a subtle electrical impulse, which, in turn, generates an electric field that is detected by the as-fabricated MoSe2/PVA device when attached to the forehead and interfaced to Open Brain-Computer Interface platform-based Cyton biosensing board. The device is also used as an ultrasensitive pressure sensor for arterial pulse pressure monitoring. This detection mechanism of the multifunctional sensor can be attributed to the piezoresistive effect of MoSe2 nanoparticles, wherein the dipoles reorient to form an internal polarization upon detection of physiological information. The strategy employed here paves the way toward replacing wet electrodes in conventional electroencephalogram (EEG)/electrocardiogram (ECG) measurements that result in skin abrasion and signal quality degradation with low-cost, reliable, skin-friendly, wearable MoSe2/PVA dry electrodes for rapid assessment.

3D designed battery-free wireless origami pressure sensor

A pressure monitoring structure is a very useful element for a wearable device for health monitoring and sports biomechanics. While pressure sensors have been studied extensively, battery-free functions working in wireless detection have not been studied much. Here, we report a 3D-structured origami-based architecture sensor for wireless pressure monitoring. We developed an architectured platform for wireless pressure sensing through inductor-capacitor (LC) sensors and a monopole antenna. A personalized smart insole with Miura-ori origami designs has been 3D printed together with conductive 3D printed sensors seamlessly. Wireless monitoring of resonant frequency and intensity changes of LC sensors have been demonstrated to monitor foot pressure for different postures. The sensitivity of the wireless pressure sensor is tunable from 15.7 to 2.1 MHz/kPa in the pressure ranges from 0 to 9 kPa and from 10 to 40 kPa, respectively. The proposed wireless pressure-sensing platform can be utilized for various applications such as orthotics, prosthetics, and sports gear.

Silk nanofibrous iontronic sensors for accurate blood pressure monitoring

Continuous and cuff-less blood pressure (BP) monitoring based on pulse transit time has been extensively explored in wearable electronics. However, both the accuracy and wearing comfort are impeded by the limited sensitivity, skin conformability and breathability of conventional pulse sensors. Here, silk nanofibrous iontronic pressure sensors made entirely of biocompatible materials were demonstrated for accurate, skin-friendly and long-term BP measurement. The sensor achieved a high sensitivity (138.5 kPa−1) by incorporating ionic deep eutectic solvents (DES) and engineering micro-structured electrodes, which enables the accurate measurement of pulse waveforms. High flexibility and gas-permeability (2056 g m-2h−1) of the sensor render a conformal contact with the skin and prevent the signal deterioration by sweat, thus improving the signal accuracy and stability during long-term on-skin BP monitoring. Together with the electrocardiogram, both systolic and diastolic BPs could be estimated with mean ± standard deviation of 0.6 ± 3.57 mmHg and 0.7 ± 3.72 mmHg, respectively, meeting the standard of Association for the Advancement of Medical Instrumentation.

A Fully Integrated Flexible Electronic System With Highly Sensitive MWCNTs Piezoresistive Array Sensors for Pressure Monitoring

Pressure ulcers are a common and costly health problem in clinical medicine, caused primarily by continuous vertical pressure on local tissues of the body. Recently, flexible devices have been used to alert pressure ulcers by continuously monitoring the pressure applied to the human skin. Although many pressure sensors provide excellent sensing performance, they still rely on uncomfortable, unstretchable systems with rigid electronics. These devices are mounted on the human body, which hinders continuous pressure monitoring. Herein, we propose a fully integrated flexible electronic system (FIFES) with highly sensitive multi-walled carbon nanotubes (MWNTs) piezoresistive array sensors for pressure monitoring, which accurately achieves external pressure signals acquisition and independently performs processing and wireless transmission. We develop a heat seal connecting technology for integrating the piezoresistive array sensors and its flexible processing circuit, which overcomes the compatibility defect of a rigid circuit board and the flexible sensors. Furthermore, the Cu–Ge metal sputtering and transferring technologies are employed to achieve an extensible circuit. The as-fabricated fully integrated electronic system has excellent flexibility, a rapid response time (the response/recovery time is 0.11/0.08 s, respectively), a wide dynamic range (6–50 kPa), and an excellent sensitivity (1.61 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for the range under the pressure of 18 kPa, 0.47 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for the range of 18–50 kPa) attributes to the optimized conical microstructures number. Owing to its excellent performance, the FIFES has extensive applications for pressure monitoring in different human epidermises, such as elbow bending and knee-bending. Also, it has immense potential applications in sleep posture monitoring and pressure ulcer warning.

Wearable Blood Pressure Sensing Based on Transmission Coefficient Scattering for Microstrip Patch Antennas.

Painless, cuffless and continuous blood pressure monitoring sensors provide a more dynamic measure of blood pressure for critical diagnosis or continuous monitoring of hypertensive patients compared to current cuff-based options. To this end, a novel flexible, wearable and miniaturized microstrip patch antenna topology is proposed to measure dynamic blood pressure (BP). The methodology was implemented on a simulated five-layer human tissue arm model created and designed in High-Frequency Simulation Software “HFSS”. The electrical properties of the five-layer human tissue were set at the frequency range (2–3) GHz to comply with clinical/engineering standards. The fabricated patch incorporated on a 0.4 mm epoxy substrate achieved consistency between the simulated and measured reflection coefficient results at flat and bent conditions over the frequency range of 2.3–2.6 GHz. Simulations for a 10 g average specific absorption rate (SAR) based on IEEE-Standard for a human arm at different input powers were also carried out. The safest input power was 50 mW with an acceptable SAR value of 3.89 W/Kg < 4W/Kg. This study also explored a novel method to obtain the pulse transit time (PTT) as an option to measure BP. Pulse transmit time is based on obtaining the time difference between the transmission coefficient scattering waveforms measured between the two pairs of metallic sensors underlying the assumption that brachial arterial geometries are dynamic. Consequently, the proposed model is validated by comparing it to the standard nonlinear Moens and Korteweg model over different artery thickness-radius ratios, showing excellent correlation between 0.76 ± 0.03 and 0.81 ± 0.03 with the systolic and diastolic BP results. The absolute risk of arterial blood pressure increased with the increase in brachial artery thickness-radius ratio. The results of both methods successfully demonstrate how the radius estimates, PTT and pulse wave velocity (PWV), along with electromagnetic (EM) antenna transmission propagation characteristics, can be used to estimate continuous BP non-invasively.

Multiparameter measuring system using fiber optic sensors for hydraulic temperature, pressure and flow monitoring

In this paper, based on the research of fiber optic sensing technology, a multiparameter measuring system for hydraulic parameter monitoring is developed and evaluated. The sensing theory, design, calibration, and installation of the proposed metal-coated fiber Bragg grating temperature sensor, fiber Bragg grating flow sensor, and Fabry-Perot pressure sensor are detailed in the paper. A special hydraulic platform is designed for system test and the parameter monitoring condition of the hydraulic platform is displayed by the graphical user interface designed by using LabVIEW. The effectiveness of the designed system is verified by analyzing and comparing the obtained data of electrical sensors and the proposed sensors installed in the hydraulic platform. Experimental results indicate that the designed system using fiber optic sensing technology can accurately detect the parameters of the hydraulic equipment, and can be potentially used for real-time detection for condition monitoring of hydraulic equipment by analyzing the characteristic parameters.

An internet of things-based automatic brain tumor detection system

Due to the advances in information and communication technologies, the usage of the internet of things (IoT) has reached an evolutionary process in the development of the modern health care environment. In the recent human health care analysis system, the amount of brain tumor patients has increased severely and placed in the 10th position of the leading cause of death. Previous state-of-the-art techniques based on magnetic resonance imaging (MRI) faces challenges in brain tumor detection as it requires accurate image segmentation. A wide variety of algorithms were developed earlier to classify MRI images which are computationally very complex and expensive. In this paper, a cost-effective stochastic method for the automatic detection of brain tumors using the IoT is proposed. The proposed system uses the physical activities of the brain to detect brain tumors. To track the daily brain activities, a portable wrist band named Mi Band 2, temperature, and blood pressure monitoring sensors embedded with Arduino-Uno are used and the system achieved an accuracy of 99.3%. Experimental results show the effectiveness of the designed method in detecting brain tumors automatically and produce better accuracy in comparison to previous approaches.

Evaluation of a cuffless watch-like sensor for 24-hour ambulatory blood pressure monitoring

Abstract Introduction Ambulatory blood pressure monitoring (ABPM) is increasingly used in clinical practice for the formal diagnosis of hypertension, and particularly indicated in cases of suspected white-coat effect, masked, or nocturnal hypertension. However, the use of cuffs for ABPM may be painful and cause discomfort, particularly at night, where it may even provoke arousal from sleep and lead to non-representative nighttime blood pressure (BP) values. Purpose To investigate the feasibility of using a cuffless watch-like photoplethysmographic (PPG) sensor for 24-hour ABPM by comparing the PPG-based BP estimates with conventional cuff-derived ABPM values. Methods Our study was approved by the local ethical committee and conducted in 70 participants (43±18 y, 35 with hypertension, 41 male) undergoing cuff-based ABPM. At the contralateral side of the cuff, a cuffless watch-like PPG sensor was worn at the wrist or upper arm. Systolic (SBP) and diastolic (DBP) BP values were estimated by pulse wave analysis on the measured PPG signals. Following a calibration procedure, the PPG-based daytime and nighttime BP estimates were compared to their cuff-based counterparts. The agreement between both methods was evaluated via the mean (bias) and standard deviation (SD) of their differences by Bland-Altman analysis. The agreement on the nocturnal dipping estimates of both devices was also assessed. Finally, the concordance rate (CR) was assessed as the percentage of dipping values showing a concordant direction (dipping vs. non-dipping) between both methods. Results The data of 4 participants were incomplete due to technical issues and had to be rejected prior to analysis. In 4 additional participants, the PPG data quality was insufficient to provide enough BP estimates, probably due to poor sensor tightening. In the remaining 62 participants, we found (see Figure 1) differences between the daytime PPG-based and cuff-based BP estimates of −0.9±3.6 mmHg and −1.4±2.9 mmHg for SBP and DBP, respectively. The differences between the nighttime estimates were −0.8±6.8 mmHg and 0.5±5.3 mmHg, resulting in dipping differences of 0.1±6.8% and −2.0±8.6% for SBP and DBP, respectively. CR on dipping was 97% for both SBP and DBP. Conclusions Good agreement was found between the PPG-based and the cuff-based daytime and nighttime BP averages, with generally negligible (∼1 mmHg) biases. The direction of dipping was highly concordant between both methods. The estimation of its amplitude showed a low bias (∼1%) but a non-negligible spread (SD), which can be in part attributed to the uncertainty on the cuff-based dipping estimates (95% confidence interval range of 12.5% and 16.5% on average for SBP and DBP, respectively), more than twice as large than their PPG-based counterparts (5.7% and 7.8%). Although our study was designed as a method-comparison feasibility study, these results encouragingly suggest that cuffless ABPM may soon become a clinical possibility. Funding Acknowledgement Type of funding sources: None. Figure 1

Real-time monitoring of pressure and temperature of oil well using a carbon-coated and bellow-packaged optical fiber sensor

A carbon-coated and bellow-packaged optical fiber sensor for high pressure and high temperature monitoring in downhole applications is developed and successfully field-applied in an oil well. Carbon-coating and bellow-packing techniques are introduced to enable the sensor to operate under the extreme conditions in downhole. Carbon-coating is aimed at preventing oil and gas from penetrating through the silica capillary that houses the sensor and also reduce the hydrogen-induced loss and capillary corrosion. The packaging with a bellows structure is designed for both efficient pressure transfer and effective isolation of external corrosive contents from direct contact with the optical fiber probe. We developed a carbon coating technique based on a CO2 laser system and implemented a bellows – diaphragm combination using laser welding. By both measurements in lab and a long-term field test in an oil well, the coated and bellow-packed sensor has shown good pressure linearity of more than 0.99999 with 0.03% F.S. repeatability and 2.9 psi resolution – demonstrating its great potential for long-term downhole dynamic monitoring.

Flexible Ultra-Thin Nanocomposite Based Piezoresistive Pressure Sensors for Foot Pressure Distribution Measurement.

Foot pressure measurement plays an essential role in healthcare applications, clinical rehabilitation, sports training and pedestrian navigation. Among various foot pressure measurement techniques, in-shoe sensors are flexible and can measure the pressure distribution accurately. In this paper, we describe the design and characterization of flexible and low-cost multi-walled carbon nanotubes (MWCNT)/Polydimethylsiloxane (PDMS) based pressure sensors for foot pressure monitoring. The sensors have excellent electrical and mechanical properties an show a stable response at constant pressure loadings for over 5000 cycles. They have a high sensitivity of 4.4 k/kPa and the hysteresis effect corresponds to an energy loss of less than 1.7%. The measurement deviation is of maximally 0.13% relative to the maximal relative resistance. The sensors have a measurement range of up to 330 kPa. The experimental investigations show that the sensors have repeatable responses at different pressure loading rates (5 N/s to 50 N/s). In this paper, we focus on the demonstration of the functionality of an in-sole based on MWCNT/PDMS nanocomposite pressure sensors, weighing approx. 9.46 g, by investigating the foot pressure distribution while walking and standing. The foot pressure distribution was investigated by measuring the resistance changes of the pressure sensors for a person while walking and standing. The results show that pressure distribution is higher in the forefoot and the heel while standing in a normal position. The foot pressure distribution is transferred from the heel to the entire foot and further transferred to the forefoot during the first instance of the gait cycle.

Flexible and wearable capacitive pressure sensor for blood pressure monitoring

A flexible pressure sensor based on a capacitive transduction mechanism having a polydimethylsiloxane (PDMS) layer incorporated between indium‐‑tin-oxide (ITO) coated flexible polyethylene terephthalate (PET) electrodes has been developed. The sensor's key parameters have been improved by increasing the dielectric layer's porosity by introducing deionized water (DIW) into it. The sensing device with a porous dielectric layer (PDMS-DIW) exhibits a 0.07%–15% relative difference in capacitance for the applied pressure range from 1 Pa to 100 kPa. The device also demonstrates improved sensitivity compared to a PDMS layer (unstructured) throughout the complete external pressure range. The device with porous PDMS layer shows an extensive operating pressure range (1 Pa to 100 kPa), high working stability, quick response (≈110 ms) and ultra-low detection limit of pressure, i.e., 1 Pa. In addition, the blood pressure monitoring was also studied, and the devices gave a signature of the oscillometric waveform for different blood pressure (BP) values. The fabricated flexible pressure sensor can be used for wearable BP devices and biological applications due to its excellent functional properties.

Additive manufacturing of high-performance carbon-composites: An integrated multi-axis pressure and temperature monitoring sensor

The additive manufacturing research confides in developing three-dimensional (3D) printing routes for the fabrication of devices with multifunctional materials in various interesting application areas such as self-healing, energy conversion/storage/harvesting, and sensing platforms. This paper reports the design optimization, fabrication, and characterization of a multi-axis pressure sensor with temperature compensation using fused filament fabrication (FFF) 3D printing of conductive carbon-based composites. Additive manufacturing offers a faster fabrication of complex structures with multiple properties such as electrical, mechanical, or thermal properties. The complex and costly metal printing can be neglected, as the 3D printing of a conductive polymer is a promising technology to utilize the electrical properties of the printed materials along with mechanical flexibilities. The present work focuses on the development of a multi-axis pressure sensor integrated with a temperature-sensing element. The pressure-sensing mechanism is based on piezoresistive behavior while temperature sensing relies on temperature-dependent resistance shift of the carbon composite. The pressure sensing part comprises a hollow structure to ensure mechanical deformation upon applied pressure while the temperature sensor is buried inside the housing material. Herein, the conductive three-dimensional printable polymer is synthesized by solution casting method with Polylactic acid (PLA), multi-walled carbon nanotubes (MWCNTs), and dichloromethane (DCM) solvent, which is transformed into filament for printing. The direction of pressure and magnitude of temperature can be evaluated separately by calibrating the responses of an applied force and temperature. Moreover, an integrated temperature sensor calibrates the shift in the electrical resistance of the pressure sensor due to the alteration in environmental temperature. The additive manufactured dual pressure and temperature sensor could open up broad applications such as human motion monitoring systems and force sensing.

Smart Contact Lenses with a Transparent Silver Nanowire Strain Sensor for Continuous Intraocular Pressure Monitoring.

Continuous intraocular pressure (IOP) monitoring can provide a paradigm shift in the management of patients with glaucoma as a facile alternative to conventional diagnostic methods. However, the low sensitivity and functional instability of current IOP sensors have limited their clinical utility in the management of glaucoma. Here, we have developed a smart contact lens integrated with a transparent silver nanowire IOP strain sensor and wireless circuits for noninvasive, continuous IOP monitoring. After confirming the robust stability of the IOP sensor within the smart contact lens in the presence of tears and repeated eyelid blink model cycles, we were able to monitor IOP changes on polydimethylsiloxane model eyes in vitro. In vivo tests demonstrated that our fully integrated wireless smart contact lens could successfully monitor the change in IOP in living rabbit eyes, which was clearly validated by the conventional invasive tonometer IOP test. Taken together, we could confirm the feasibility of our smart contact lens as a noninvasive platform for continuous IOP monitoring of glaucoma patients.