Breath Sensor Research Articles

Sensing gastric cancer via point‐of‐care sensor breath analyzer

Detection of disease by means of volatile organic compounds from breath samples using sensors is an attractive approach to fast, noninvasive and inexpensive diagnostics. However, these techniques are still limited to applications within the laboratory settings. Here, we report on the development and use of a fast, portable, and IoT-connected point-of-care device (so-called, SniffPhone) to detect and classify gastric cancer to potentially provide new qualitative solutions for cancer screening. A validation study of patients with gastric cancer, patients with high-risk precancerous gastric lesions, and controls was conducted with 2 SniffPhone devices. Linear discriminant analysis (LDA) was used as a classifying model of the sensing signals obatined from the examined groups. For the testing step, an additional device was added. The study group included 274 patients: 94 with gastric cancer, 67 who were in the high-risk group, and 113 controls. The results of the test set showed a clear discrimination between patients with gastric cancer and controls using the 2-device LDA model (area under the curve, 93.8%; sensitivity, 100%; specificity, 87.5%; overall accuracy, 91.1%), and acceptable results were also achieved for patients with high-risk lesions (the corresponding values for dysplasia were 84.9%, 45.2%, 87.5%, and 65.9%, respectively). The test-phase analysis showed lower accuracies, though still clinically useful. Our results demonstrate that a portable breath sensor device could be useful in point-of-care settings. It shows a promise for detection of gastric cancer as well as for other types of disease. A portable sensor-based breath analyzer for detection of gastric cancer can be used in point-of-care settings. The results are transferrable between devices via advanced IoT technology. Both the hardware and software of the reported breath analyzer could be easily modified to enable detection and monitirng of other disease states.

Durability of Abstinence After Completing a Comprehensive Digital Smoking Cessation Program Incorporating a Mobile App, Breath Sensor, and Coaching: Cohort Study.

BackgroundDespite decreasing prevalence over the last several decades, cigarette smoking remains the leading cause of preventable death and disease, underscoring the need for innovative, effective solutions. Pivot is a novel, inclusive smoking cessation program designed for smokers along the entire spectrum of readiness to quit. Pivot leverages proven methods and technological advancements, including a personal portable breath carbon monoxide sensor, smartphone app, and in-app text-based coaching. We previously reported outcomes from the end of active Pivot program participation in 319 adult smokers. Herein, we report longer-term follow up in this cohort.ObjectiveThe aim of this study was to assess and report participant outcomes 3 months after completion of Pivot, including smoking behavior, quit rates, continuous abstinence rates and durability, and predictors of abstinence.MethodsThis prospective remote cohort study included US-based cigarette smokers aged 18 to 65 years who smoked ≥5 cigarettes per day (CPD). Three months after completion of active participation in Pivot, final follow-up data were collected via an online questionnaire. Outcomes included smoking behavior (CPD and quit attempts), self-reported quit rates (7- and 30-day point prevalence abstinence [PPA]), and continuous abstinence rates (proportion who achieved uninterrupted abstinence) and duration. Exploratory regression analyses were performed to identify baseline characteristics associated with achievement of 7-day PPA, 30-day PPA, and continuous abstinence.ResultsA total of 319 participants completed onboarding (intention-to-treat [ITT]); 288/319 participants (90.3%) completed follow up (completers) at a mean of 7.2 (SD 1.2) months after onboarding. At final follow up, CPD were reduced by 52.6% (SE 2.1; P<.001) among all 319 participants, and most completers (152/288, 52.8%) reduced their CPD by at least 50%. Overall, most completers (232/288, 80.6%) made at least one quit attempt. Quit rates increased after the end of Pivot; using ITT analyses, 35.4% (113/319) achieved 7-day PPA and 31.3% (100/319) achieved 30-day PPA at final follow up compared with 32.0% (102/319) and 27.6% (88/319), respectively, at the end of the Pivot program. Continuous abstinence was achieved in about a quarter of those who onboarded (76/319, 23.8%) and in most who reported 30-day PPA at the end of Pivot (76/88, 86.4%), with a mean abstinence duration of 5.8 (SD 0.6) months. In exploratory regression analyses, lower baseline CPD, more positive baseline attitudes reflecting higher self-efficacy (higher confidence to quit and lower perceived difficulty of quitting), and higher education were associated with achieving abstinence.ConclusionsThis study provides the first longer-term outcomes of the Pivot smoking cessation program. At final follow up, quit rates increased and continuous abstinence was favorable; the majority who achieved abstinence at the end of Pivot sustained abstinence throughout follow up. Decreases in CPD persisted and most participants made a quit attempt. Overall, final follow-up outcomes were stable or improved when compared to previous outcomes from the end of the program. These findings validate earlier results, and suggest that Pivot is an effective and durable solution for smoking cessation.Trial RegistrationClinicalTrials.gov NCT03295643; https://clinicaltrials.gov/ct2/show/NCT03295643

Transparent flexible graphene quantum dot-(PVDF-HFP) piezoelectric nanogenerator

Herein, we report highly sensitive graphene quantum dot (GQDs) reinforced poly (vinylidene fluoride)-co-hexafluoride propylene (PVDF-HFP) based flexible piezoelectric nanogenerator for the first time. Formation of β-phase in GQDs /PVDF-HFP composite film was confirmed using XRD diffraction and FT-IR spectroscopy techniques. Flexible transparent piezoelectric nanogenerator fabricated from the GQDs/PVDF-HFP composite film exhibits very high output voltage of 6 V and output current of 25 nA compared to signal generated from pristine PVDF-HFP nanogenerator. The drastic improvement in the PVDF-HFP may be attributed to the alignment of electric dipoles induced by the local electric field cause by conductive GQDs. Performance of GQDs/PVDF-HFP has also been real time demonstrated as self-powered human breathing and finger movement sensors which make it suitable for promising wearable energy harvester and for powering nanosystems.

Silver Enhances Hematite Nanoparticles Based Ethanol Sensor Response and Selectivity at Room Temperature.

Gas sensors are fundamental for continuous online monitoring of volatile organic compounds. Gas sensors based on semiconductor materials have demonstrated to be highly competitive, but are generally made of expensive materials and operate at high temperatures, which are drawbacks of these technologies. Herein is described a novel ethanol sensor for room temperature (25 °C) measurements based on hematite (α‑Fe2O3)/silver nanoparticles. The AgNPs were shown to increase the oxide semiconductor charge carrier density, but especially to enhance the ethanol adsorption rate boosting the selectivity and sensitivity, thus allowing quantification of ethanol vapor in 2–35 mg L−1 range with an excellent linear relationship. In addition, the α-Fe2O3/Ag 3.0 wt% nanocomposite is cheap, and easy to make and process, imparting high perspectives for real applications in breath analyzers and/or sensors in food and beverage industries. This work contributes to the advance of gas sensing at ambient temperature as a competitive alternative for quantification of conventional volatile organic compounds.

Highly Sensitive Breath Sensor Based on Sonochemically Synthesized Cobalt-Doped Zinc Oxide Spherical Beads

Highly Sensitive Breath Sensor Based on Sonochemically Synthesized Cobalt-Doped Zinc Oxide Spherical Beads

Moist-Induced Electricity Generation by Electrospun Cellulose Acetate Membranes with Optimized Porous Structures.

Harvesting energy from moist in the atmosphere has recently been demonstrated as an effective manner for a portable power supply to meet the ever-increasing demands of energy consumption. Porous materials are shown to have great potential in moist-induced electricity generation. Herein, we report moist-induced electricity generation by electrospun cellulose acetate (CA) membranes with optimized porous structures. We show that the pore size and porosity of CA membranes can be readily tuned via a facile compression and annealing process, and the effect of pore features on the output voltages can thus be investigated systematically. We find that, at a relatively high porosity, the electricity-generation performance can be further enhanced by constructing a smaller pore to form more nanochannels. Porous CA membranes, with an optimized porosity of 52.6% and a pore diameter less than 250 nm, are prepared to construct moist-induced electricity generators, which can be applied as breath sensors and can power up calculator operation. The current study provides insights for the construction of porous materials with different pore characteristics for moist-induced electricity generation, especially in the exploration of more efficient and low-cost porous materials for large-scale practical application of the portable power supply.

Metabolomics and a breath sensor identify acetone as a biomarker for heart failure

Abstract Introduction Metabolomics delivers more biological and clinical insight than targeted investigations. We applied metabolomics to patients with heart failure (HF) with reduced ejection fraction (HFrEF). Methods 46 patients with HFrEF and 20 controls underwent metabolomic profiling, including liquid/gas chromatography mass spectrometry (LC-MS/GC-MS), nuclear magnetic resonance (NMR) metabolomics and solid-phase microextraction (SPME) volatilomics in plasma and urine. HFrEF was defined using left ventricular global longitudal strain (GLS) &amp;lt;18%, ejection fraction &amp;lt;50% and NTproBNP ≥35 pmol/L. A low cost consumer breath acetone (BrACE) sensor validated SPME results in 69 patients. Results 34 metabolites were identified by GCMS, 33 by LCMS and 2 volatiles by SPME (acetone, 2-pentanone in plasma and urine). Alanine, aspartate and glutamate, citric acid cycle, arginine biosynthesis, glyoxylate and dicarboxylate metabolism were altered in HFrEF. Plasma acetone correlated with NT-proBNP (r=0.59, 95% CI 0.4 to 0.7), triacylglycerol (55:9), 2-oxovaleric and cis-aconitic acid, involved with ketone metabolism and mitochondrial energetics. BrACE &amp;gt;1.5 ppm discriminated HF from other cardiac pathology (AUC 0.88, 95% CI 0.77 to 0.99, P&amp;lt;0.0001). Conclusion Breath acetone was detectable in HFrEF patients using a consumer sensor ($1/test) and although not cardiac specific, discriminated HF from other cardiac pathology. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Health Research Council of New Zealand

Fabrication of piezoresistive Si nanorod-based pressure sensor arrays: A promising candidate for portable breath monitoring devices

This paper reports on the controlled fabrication of a highly sensitive piezoresistive sensor by using Si nanorod (NR) arrays. An efficient, large-area, scalable strategy was adopted to fabricate the pressure sensors by incorporating chemically etched, high-aspect-ratio, vertical Si NR arrays between two thin Au layers. The piezoresistive properties corresponding to dimension- and position-controlled and randomly etched, closely packed, and thin Si NR arrays were exploited to fabricate the small, portable, and device-compatible pressure sensors. The Si-NR-based piezoresistive sensors exhibited a high sensitivity of 0.49 MPa −1 , thereby demonstrating its superiority over other unconventional piezoresistive nanomaterials such as Si with different configurations of nanostructures. Furthermore, the sensors exhibited a large variation (~45%) in the current at a constant bias voltage of 2 V under a weak applied pressure corresponding to an inert gas flow of 5 sccm. The excellent pressure sensing performance of the piezoresistive Si NRs enabled the efficient detection of changes corresponding to the human breathing pattern. In particular, the key advantages of such pressure sensors is the simple, inexpensive, and scalable fabrication process; high sensitivity with ultra-low-pressure detection; and excellent ambient stability (>several months) with a high durability pertaining to more than 1,000 cycles of pressure loading/unloading. Furthermore, we demonstrated the ability of the pressure sensor to act as a portable human breath sensor to monitor respiratory parameters in a noninvasive and personalized manner. The results can provide direction for the realization of next-generation breath-sensing gadgets and other leading-edge applications in the domain of electronic and healthcare devices. • Chemically etched, dimension- and position-controlled Si nanorod arrays are utilized as pressure sensors. • Piezoresistivity in mesoporous Si nanorod is revealed to achieve a high-pressure sensitivity. • The pressure sensor detects a tiny flow of inert gas efficiently. • Demonstrated the pressure sensor’s ability to act as a portable human breath sensor.

High-Performance Ultrafast Humidity Sensor Based on Microknot Resonator-Assisted Mach-Zehnder for Monitoring Human Breath.

Monitoring the dynamic humidity requires sensors with fast response and anti-electromagnetic interference, especially for human respiration. Here, an ultrafast fiber-optic breath sensor based on the humidity-sensitive characteristics of gelatin film is proposed and experimentally demonstrated. The sensor consists of a microknot resonator superimposed on a Mach-Zehnder (MZ) interferometer produced by a tapered single-mode fiber, which has an ultrafast response (84 ms) and recovery time (29 ms) and a large dynamic transmission range. The humidity in dynamic ambient causes changes in the refractive index of gelatin coating, which could trigger spectral intensity transients that can be explicitly distinguished between the two states. The sensing principle is analyzed using the traditional transfer-matrix analysis method. The influence of coating thickness on the sensor's trigger threshold is further investigated. Experiments on monitoring breath patterns indicate that the proposed breath sensor has high repeatability, reliability, and validity, which enable many other potential applications such as food processing, health monitoring, and other biomedical applications.

Assessment of a Personal Interactive Carbon Monoxide Breath Sensor in People Who Smoke Cigarettes: Single-Arm Cohort Study.

BackgroundTobacco use is the leading cause of preventable morbidity and mortality. Existing evidence-based treatments are underutilized and have seen little recent innovation. The success of personal biofeedback interventions in other disease states portends a similar opportunity in smoking cessation. The Pivot Breath Sensor is a personal interactive FDA-cleared (over-the-counter) device that measures carbon monoxide (CO) in exhaled breath, enabling users to link their smoking behavior and CO values, and track their progress in reducing or quitting smoking.ObjectiveThe objective of this study is to assess the Pivot Breath Sensor in people who smoke cigarettes, evaluating changes in attitudes toward quitting smoking, changes in smoking behavior, and use experience.MethodsUS adults (18-80 years of age, ≥10 cigarettes per day [CPD]) were recruited online for this remote 12-week study. Participants completed a screening call, informed consent, and baseline questionnaire, and then were mailed their sensor. Participants were asked to submit 4 or more breath samples per day and complete questionnaires at 1-4, 8, and 12 weeks. Outcomes included attitudes toward quitting smoking (Stage of Change, success to quit, and perceived difficulty of quitting), smoking behavior (quit attempts, CPD reduction, and 7-, 30-day point prevalence abstinence [PPA]), and use experience (impact and learning).ResultsParticipants comprised 234 smokers, mean age 39.9 (SD 11.3) years, 52.6% (123/234) female, mean CPD 20.3 (SD 8.0). The 4- and 12-week questionnaires were completed by 92.3% (216/234) and 91.9% (215/234) of participants, respectively. Concerning attitude outcomes, at baseline, 15.4% (36/234) were seriously thinking of quitting in the next 30 days, increasing to 38.9% (84/216) at 4 weeks and 47.9% (103/215) at 12 weeks (both P<.001). At 12 weeks, motivation to quit was increased in 39.1% (84/215), unchanged in 54.9% (118/215), and decreased in 6.0% (13/215; P<.001). Additional attitudes toward quitting improved from baseline to 12 weeks: success to quit 3.3 versus 5.0 (P<.001) and difficulty of quitting 2.8 versus 4.3 (P<.001). Regarding smoking behavior, at 4 weeks, 28.2% (66/234) had made 1 or more quit attempts (≥1 day of abstinence), increasing to 48.3% (113/234) at 12 weeks. At 4 weeks, 23.1% (54/234) had reduced CPD by 50% or more, increasing to 38.5% (90/234) at 12 weeks. At 12 weeks, CPD decreased by 41.1% from baseline (P<.001), and 7- and 30-day PPA were 12.0% (28/234) and 6.0% (14/234), respectively. Concerning use experience, 75.3% (171/227) reported the sensor increased their motivation to quit. More than 90% (>196/214) indicated the sensor taught them about their CO levels and smoking behavior, and 73.1% (166/227) reported that seeing their CO values made them want to quit smoking.ConclusionsUse of the Pivot Breath Sensor resulted in a significant increase in motivation to quit, a reduction in CPD, and favorable quit attempt rates. These outcomes confer increased likelihood of quitting smoking. Accordingly, the results support a role for biofeedback via personal CO breath sampling in smoking cessation.Trial RegistrationClinicalTrials.gov NCT04133064; https://clinicaltrials.gov/ct2/show/NCT04133064

Power saving by a smart breath sensor working in non-connectable advertising mode

The paper presents an energy-saving breath monitoring system based on smart sensors. The current consumption by BLE modules was limited by reducing transmission frequency, which was related to the number of PDUs transmitted per unit of time. Each time 20 consecutive measurement results were saved in the PDUs. Therefore, the measurement frequency was 20 times higher than the transmission frequency. Appropriate configuration of the PDU transmission interval allows to extend the working time of battery-powered sensors by approx. 45 %, without reducing the accuracy of mapping individual breathing cycle curves, both for normal (10−20BPM) and highly accelerated (even over 100BPM) breathing. Statistical analysis showed that a 10-fold reduction of the measurement frequency (from 200 Hz to 20 Hz), allowing to extend the system working time by the mentioned 45 %, does not significantly (p > 0.05) affect the shape of the recorded breathing cycle curves, both for normal and highly accelerated breathing. The paper also presents the design of the wearable sensor, intended for cooperation with medium oxygen concentration masks.

Breathing process monitoring with a biaxially oriented polypropylene film based fiber Fabry–Perot sensor

The breathing process monitoring with a biaxially oriented polypropylene (BOPP) film based fiber Fabry–Perot (F–P) sensor is presented. The fiber F–P sensor is fabricated with 3-D printing technology and fixed on a medical respirator for breathing process monitoring. Due to the low Young’s modulus of the BOPP film and its thinner thickness, the breathing sensor shows the high pressure sensitivity of -0.581 nm/Pa. By monitoring its intensity response to the pressure induced by breathing, the breathing process can be monitored accurately, including respiratory waveform, respiratory rate, inspiratory duration and amplitude, expiratory duration and amplitude, and inspiratory and expiratory rhythm. Since the sensor is all fiber design with the inherent advantages of small size, anti-electromagnetic interference, green environmental protection, pollution-free and no harm to body, it is expected to be widely used in respiratory disease monitoring.

When will we ditch the AHI?

When will we ditch the AHI?

Stable and Biocompatible Carbon Nanotube Ink Mediated by Silk Protein for Printed Electronics.

Ink-based processes, which enable scalable fabrication of flexible devices based on nanomaterials, are one of the practical approaches for the production of wearable electronics. However, carbon nanotubes (CNTs), which possess great potential for flexible electronics, are facing challenges for use in inks due to their low dispersity in most solvents and suspicious cytotoxicity. Here, a stable and biocompatible CNT ink, which is stabilized by sustainable silk sericin and free from any artificial chemicals, is reported. The ink shows stability up to months, which can be attributed to the formation of sericin-CNT (SSCNT) hybrid through non-covalent interactions. It is demonstrated that the SSCNT ink can be used for fabricating versatile circuits on textile, paper, and plastic films through various techniques. As proofs of concept, electrocardiogram electrodes, breath sensors, and electrochemical sensors for monitoring human health and activity are fabricated, demonstrating the great potential of the SSCNT ink for smart wearables.

Unobtrusive Screening of Central Sleep Apnea From Pressure Sensors Measurements: A Patient-Specific Longitudinal Study

Historically, the lack of patients’ sleep histories has caused low identification of sleep apnea (SA) and referral rates. Moreover, the costly and time-consuming nature of polysomnography (PSG) as a standard clinical test for detecting SA and the lack of sleep clinics has created a demand for suitable home-based monitoring devices. Pressure measurement using a pressure sensitive mat (PSM) can address the challenges found in current sleep-monitoring solutions. The noncontact PSM has a potential to replace obtrusive breathing sensors in the sleep lab and to be used as a prescreening tool for patients suspected of having SA. Applying classical support vector machine (SVM), this article presents a personalized system based on the measurements of each patient to detect central SA (CSA) events and monitor sleep characteristics longitudinally. For this purpose, sensor set-ups were installed in nine seniors’ homes to collect unsupervised pressure data in approximately one year ranging from 8 to 12 months. Cost-based and resampling-based approaches were examined to combat imbalanced data. The results showed that the cost-based method outperformed other methods. Next, the patient-specific system was used to determine the total number of CSA events, as well as their starting time and duration in each day. The SA severity was measured by the central apnea index (CAI). In addition, other sleep characteristics such as bed occupancy (BO), day clock, and night clock were extracted from the PSM measurements. The impact of longitudinal sleep monitoring could be in tracking SA treatment progression, and possibly providing information on the interaction between SA and other disease progressions.

Selective Breath Sensors for Metabolic Monitoring

Introduction Despite a growing diagnostic toolset and a plethora of preventative and therapeutic interventions, a major challenge remains the control of epidemic diseases like obesity, diabetes or cancer. Great promise bears the current transformation of healthcare from disease-reactive to predictive, preventive, personalized and participatory - the so-called “4P” medicine [1]. Breath analysis could play a key role in this by providing on-demand critical health data. For daily breath analysis in wide-spread populations, simple-in-use and portable breath detectors are required. For this purpose, chemoresistive sensors are quite attractive due to their compact design, low cost and low power consumption being ideal for integration into handheld devices [2]. Here, I will describe recent progress on the development of selective/single-molecule breath sensors. In particular, I will showcase our recent in-vivo tests of Si-doped WO3 breath acetone sensors in a clinical environment during ketogenic dieting (KD) [3]. Finally, I will update on our newest development on orthogonal sensor arrays and present their application to sniff breath- and skin-emitted tracers (including acetone, isoprene and ammonia) for search & rescue applications [4]. Methods The sensor is based on a Si-doped WO3 nanoparticle films prepared by flame spray pyrolysis (FSP). Obtained nanoparticles were deposited directly by thermophoresis onto interdigitated Pt electrodes. End-tidal breath was extracted in a monitored and reproducible fashion with a tailor-made and modular sampler described in detail elsewhere [5]. The acetone sensor was mounted on a Macor holder, installed inside a Teflon chamber and fed with 130 mL min-1 from the sampler with a pump (SP 135 FZ, Schwarzer Precision). An additional line was connected just before the acetone sensor chamber to extract samples for the QMS (QMS 422, ThermoStarTM, Pfeiffer Vacuum). Healthy non-smokers free from respiratory or cardiovascular disease were included in this study. Each volunteer was informed about the experimental protocol prior to the test, gave written consent and could interrupt the test or withdraw consent anytime. The participants followed a fat:(carbohydrate+protein) 4:1 KD based on the Johns Hopkins protocol for 36 h including overnight fasting periods. Results and Conclusions Eleven volunteers (five female and six male) with a median age (± SD) of 22.7 (± 2.0) years participated in this study. Their body mass index was 22.4 (± 3.3) kg/m2. All volunteers had office jobs and were rather inactive. With the compact and inexpensive sensor, the individual breath acetone dynamics were monitored accurately up to concentrations of 66 ppm, in good agreement with mass spectrometry. The breath acetone dynamic reflected well the status of ketosis, as indicated by blood BOHB. Most interestingly, strong differences in individual breath and blood profiles were identified between the volunteers despite identical KD conditions. These were correctly recognized by the breath acetone sensor including patterns possibly associated to low tolerance to the KD protocol.As a result, this breath sensor is promising as a portable ketosis monitor. It has broad application as ketogenic diet is a proven medical treatment of refractory epilepsy (i.e. drug-resistant) [6] occurring in ~30% of the approx. 50 million epileptics worldwide. Also, it is an effective therapy for weight loss with growing interest to treat obesity-associated metabolic disorders [7] (e.g. diabetes or fatty liver disease), acts anti-inflammatory [8] and is even beneficial for athletes to improve their endurance performance by altering fuel preference [9].

Handheld Sensor for Point-of-Care Methanol Detection in Breath and Liquor

Handheld Sensor for Point-of-Care Methanol Detection in Breath and Liquor

Constant Electricity Generation in Nanostructured Silicon by Evaporation-Driven Water Flow.

Recently, hydrovoltaic technology emerged as a novel renewable energy harvesting method, which dramatically extends the capability to harvest water energy. However, the urgent issue restricting its device performance is poor carrier transport properties of the solid surface if large charged interface is considered simultaneously. Herein, a hydrovoltaic device based on silicon nanowire arrays (SiNWs), which provide large charged surface/volume ratio and excellent carrier transport properties, yields sustained electricity by a carrier concentration gradient induced by evaporation-induced water flow inside nanochannels. The device can yield direct current with a short-circuit current density of over 55 μA cm-2 , which is three orders larger than a previously reported analogous device (approximately 40 nA cm-2 ). Moreover, it exhibits a constant output power density of over 6 μW cm-2 and an open-circuit voltage of up to 400 mV. Our finding may pave a way for developing energy-harvesting devices from ubiquitous evaporation-driven internal water flow in nature with semiconductor material of silicon.

Bolometric Effect Enhanced Ultrafast Graphene Based Do-It-Yourself Wearable Respiration Sensor for Personal Healthcare Monitoring

The report demonstrates the Near Infrared (NIR) illuminated enhanced breath sensor utilizing direct writing of solvent free graphene pencil on biodegradable cellulose paper to monitor different respiration patterns and rate for non-invasive personal healthcare monitoring. Various breath patterns such as deep, slow and fast breathing were tested and interestingly the fabricated sensor was able to distinguish the pattern based on the frequency and the amplitude of current peaks obtained. Also, the fabricated sensor was able to identify the hydration level of the individual where in 25–35 % decrement in the sensor current value was observed when the measurements were performed after consuming water. To enhance the desorption process of water molecules, breath sensing was performed under NIR illumination where the photo response was bolometric in nature which results in the faster desorption process due to the heat generated. The fall time observed under NIR illumination was 1.32sec and without NIR illumination was 2.01 sec suggesting a 34% improvement in the performance of the fabricated sensor. The change in the current under human breath exhalation is due to the electron transfer process and swelling of the graphene sheets. Detailed conduction mechanism of graphene under NIR illumination is presented suggesting the combination of both bolometric nature and direct photoconductivity with the former predominantly affecting the conductivity. The successful demonstration of such low-cost, do it yourself wearable enhanced respiration sensor is a major step ahead in the non-invasive personal healthcare monitoring and hold potential for commercialization.

The Piezoresistive Highly Elastic Sensor Based on Carbon Nanotubes for the Detection of Breath.

Wearable electronic sensor was prepared on a light and flexible substrate. The breathing sensor has a broad assumption and great potential for portable devices in wearable technology. In the present work, the application of a flexible thermoplastic polyurethane/multiwalled carbon nanotubes (TPU/MWCNTs) strain sensor was demonstrated. This composite was prepared by a novel technique using a thermoplastic filtering membrane based on electrospinning technology. Aqueous dispersion of MWCNTs was filtered through membrane, dried and then welded directly on a T-shirt and encapsulated by a thin silicone layer. The sensing layer was also equipped by electrodes. A polymer composite sensor is capable of detecting a deformation by changing its electrical resistance. A T-shirt was capable of analyzing a type, frequency and intensity of human breathing. The sensitivity to the applied strain of the sensor was improved by the oxidation of MWCNTs by potassium permanganate (KMnO4) and also by subsequent application of the prestrain.