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Comparison of the electrical signals acquired from the previously-reported sensor patch, and a commercial respiratory effort transducer under (RET) (a) static (sitting), and (b) dynamic (walking) conditions.
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This study reports a piezoelectric poly(vinylidene fluoride) (PVDF) polymer-based sensor patch for respiration detections in dynamic walking condition. The working mechanism of respiration signal generation is based on the periodical deformations on a human chest wall during the respiratory movements, which in turn mechanically stretch the piezoele...
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Context 1
... our previous study, we have proposed a simple, small-size, light-weight, and user-friendly PVDF polymer-based sensor patch for respiration monitoring [17] as described in the introduction section. In the design, the sensor patch was composed of three layers including a PDMS cover module layer, a PVDF sensing film layer, and a Mylar layer (a hard polyester film). In order to enhance the signal amplitude, the PVDF layer was bonded with the Mylar layer in a curved structure and it can be freely movable. In that system, the PVDF sensing layer can be modeled as a mass-spring mechanical system without damping effect. In general, an undamped mechanical system normally has the characteristic response of large overshoot and long settling time. Hence, the mechanical amplitude of the PVDF layer could be enhanced by large overshoot when the stimulated oscillation was in a regularly repeated manner. Higher mechanical deformation could in turn generate higher electrical signals, as shown in our previous work [17]. It was reported that the electrical signals were around 151% of that based on the sensor with flat PVDF structure under static respiration measurement [17]. However, response with long settling time generated disturbed harmonic oscillation when the stimulated oscillation frequency and the natural frequency of the PVDF layer were not the same. In this situation, the measurement under static conditions (e.g., sitting or sleeping) was still acceptable because the stimulated oscillation frequency was fixed, as shown in Figure 3a. The disturbed harmonic oscillation could be filtered out by the signal conditioning post-process. When the measurement was under dynamic conditions (e.g., walking), conversely, the mechanical response was highly influenced by such disturbed harmonic oscillation with the combination of various frequencies. The generated electrical signals may not represent the actual respiration motions, as shown in Figure 3b. Therefore, the design of the previously-reported sensor patch might not be suitable for the respiration detection particularly under dynamic condition due to noise problem. The published Sensor Patch RET In order to tackle the abovementioned technical problem, the proposed PVDF-based sensor patch was developed for the respiration measurement under dynamic walking conditions. In the design, a thin PVDF sensing layer was entirely encapsulated by two elastic PDMS cover layers in order to constraint its free movements which is different from the design of the previously-reported sensor patch [17]. Based on the structure design, the PVDF sensing layer can be modeled as a mass-spring-damper mechanical system. The phenomenon of large overshoot and long settling time normally occurred in an undamped system could be, to great extent, down-regulated. Since the overshoot was reduced, the mechanical amplitude of PVDF sensing layer was accordingly reduced. Therefore, the amplitude of electrical signal output might be compromised. Nevertheless, the reduction of settling time could eliminate the disturbed harmonic oscillation, which could enable the proposed sensor patch to significantly prevent dynamic noises. In order to justify this hypothesis, experimental investigations were carried out. Figure 4a,b revealed the respiration signals generated by the proposed sensor patch under static and dynamic conditions, respectively. It can be clearly found that the respiration signals generated by the proposed sensor patch were in concordance with the commercial RET under the two operating conditions explored. This could suggest that the proposed sensor patch was able to faithfully respond to the physiological movements of respirations under both conditions. For comparison of the respiratory rates measured by the proposed sensor patch and the commercially-available device (commercial respiratory effort transducer (RET)), further experiments were conducted. In this evaluation, four individuals including two males and two females were tested with the same experimental conditions. Table 1 disclosed the measurement results obtained by the proposed sensor patch and a commercial RET under static and dynamic conditions. It was found that there was no statistical difference (p > 0.05) between both measurement techniques, indicating the proposed sensor patch holds great promise to faithfully detect respiration signals both in static and dynamic conditions. Subsequent large-scale clinical study might be required to further confirm its accuracy and clinical utility. Based on above experimental evaluations, overall, it can be concluded that, the PVDF-based sensor patches with two different designs (i.e., the previously-reported and the proposed PVDF-based sensor patch) could be selected for the respiratory measurements under different implementing conditions. For the applications situating in static conditions (e.g., sleeping or sitting), for example, the previously-reported sensor patch is suitable because it could generate higher electrical signals for improving the signal-to-noise ratio. On the other hand, the sensor patch proposed in this study could be the ideal choice for the detection of respiration under dynamic conditions (e.g., walking) because of its capability to prevent the generation of dynamic noises. As a whole, this study has presented a simple and portable PVDF-based sensor patch that is capable of detecting respiration signals under static sitting and dynamic walking conditions. These technical features make it an ideal sensing device for the monitoring of respiration in patient home care. In terms of future perspectives, a wireless signal transmission mechanism can be integrated in the sensor patch. By then, the signals generated can be transmitted to a smartphone or other hand-held devices, in which a built-in software for signal processing can be used to analyze the relevant signals. Table 1. Comparison of the respiration rates measured by the proposed sensor patch, and commercial respiratory effort transducer (RET) under static (sitting) and dynamic (walking) conditions; unit: times· min −1 . The proposed Sensor Patch ...
Context 2
... our previous study, we have proposed a simple, small-size, light-weight, and user-friendly PVDF polymer-based sensor patch for respiration monitoring [17] as described in the introduction section. In the design, the sensor patch was composed of three layers including a PDMS cover module layer, a PVDF sensing film layer, and a Mylar layer (a hard polyester film). In order to enhance the signal amplitude, the PVDF layer was bonded with the Mylar layer in a curved structure and it can be freely movable. In that system, the PVDF sensing layer can be modeled as a mass-spring mechanical system without damping effect. In general, an undamped mechanical system normally has the characteristic response of large overshoot and long settling time. Hence, the mechanical amplitude of the PVDF layer could be enhanced by large overshoot when the stimulated oscillation was in a regularly repeated manner. Higher mechanical deformation could in turn generate higher electrical signals, as shown in our previous work [17]. It was reported that the electrical signals were around 151% of that based on the sensor with flat PVDF structure under static respiration measurement [17]. However, response with long settling time generated disturbed harmonic oscillation when the stimulated oscillation frequency and the natural frequency of the PVDF layer were not the same. In this situation, the measurement under static conditions (e.g., sitting or sleeping) was still acceptable because the stimulated oscillation frequency was fixed, as shown in Figure 3a. The disturbed harmonic oscillation could be filtered out by the signal conditioning post-process. When the measurement was under dynamic conditions (e.g., walking), conversely, the mechanical response was highly influenced by such disturbed harmonic oscillation with the combination of various frequencies. The generated electrical signals may not represent the actual respiration motions, as shown in Figure 3b. Therefore, the design of the previously-reported sensor patch might not be suitable for the respiration detection particularly under dynamic condition due to noise problem. The published Sensor Patch RET In order to tackle the abovementioned technical problem, the proposed PVDF-based sensor patch was developed for the respiration measurement under dynamic walking conditions. In the design, a thin PVDF sensing layer was entirely encapsulated by two elastic PDMS cover layers in order to constraint its free movements which is different from the design of the previously-reported sensor patch [17]. Based on the structure design, the PVDF sensing layer can be modeled as a mass-spring-damper mechanical system. The phenomenon of large overshoot and long settling time normally occurred in an undamped system could be, to great extent, down-regulated. Since the overshoot was reduced, the mechanical amplitude of PVDF sensing layer was accordingly reduced. Therefore, the amplitude of electrical signal output might be compromised. Nevertheless, the reduction of settling time could eliminate the disturbed harmonic oscillation, which could enable the proposed sensor patch to significantly prevent dynamic noises. In order to justify this hypothesis, experimental investigations were carried out. Figure 4a,b revealed the respiration signals generated by the proposed sensor patch under static and dynamic conditions, respectively. It can be clearly found that the respiration signals generated by the proposed sensor patch were in concordance with the commercial RET under the two operating conditions explored. This could suggest that the proposed sensor patch was able to faithfully respond to the physiological movements of respirations under both conditions. For comparison of the respiratory rates measured by the proposed sensor patch and the commercially-available device (commercial respiratory effort transducer (RET)), further experiments were conducted. In this evaluation, four individuals including two males and two females were tested with the same experimental conditions. Table 1 disclosed the measurement results obtained by the proposed sensor patch and a commercial RET under static and dynamic conditions. It was found that there was no statistical difference (p > 0.05) between both measurement techniques, indicating the proposed sensor patch holds great promise to faithfully detect respiration signals both in static and dynamic conditions. Subsequent large-scale clinical study might be required to further confirm its accuracy and clinical utility. Based on above experimental evaluations, overall, it can be concluded that, the PVDF-based sensor patches with two different designs (i.e., the previously-reported and the proposed PVDF-based sensor patch) could be selected for the respiratory measurements under different implementing conditions. For the applications situating in static conditions (e.g., sleeping or sitting), for example, the previously-reported sensor patch is suitable because it could generate higher electrical signals for improving the signal-to-noise ratio. On the other hand, the sensor patch proposed in this study could be the ideal choice for the detection of respiration under dynamic conditions (e.g., walking) because of its capability to prevent the generation of dynamic noises. As a whole, this study has presented a simple and portable PVDF-based sensor patch that is capable of detecting respiration signals under static sitting and dynamic walking conditions. These technical features make it an ideal sensing device for the monitoring of respiration in patient home care. In terms of future perspectives, a wireless signal transmission mechanism can be integrated in the sensor patch. By then, the signals generated can be transmitted to a smartphone or other hand-held devices, in which a built-in software for signal processing can be used to analyze the relevant signals. Table 1. Comparison of the respiration rates measured by the proposed sensor patch, and commercial respiratory effort transducer (RET) under static (sitting) and dynamic (walking) conditions; unit: times· min −1 . The proposed Sensor Patch ...
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Piezoelectric sensors whose sensing performances can be flexibly regulated hold significant promise for efficient signal-acquisition applications in the healthcare field. The existing methods for regulating the properties of polyvinylidene fluoride (PVDF) films mainly include material modification and structural design. Compared to material modific...
Citations
... PVDF flexible pressure sensors, characterized by high sensitivity, excellent flexibility, and strong biocompatibility, exhibit extensive potential applications in health monitoring, wearable devices, and electronic skin. In 2015, Lei et al. [15] designed a PVDF sensor patch for monitoring respiratory signals during dynamic walking. In 2018, Sekine T and collaborators [16] utilized a polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) as the sensitive layer to develop a fully printed, wearable pulse sensor capable of monitoring pulse signals on the skin. ...
Hypertension is a common cause of cardiovascular diseases, closely associated with the high mortality and disability rates of cardiovascular diseases such as stroke and coronary heart disease. Therefore, developing a comfortable and sustainable device for monitoring human pulse signals holds practical significance for the prevention and treatment of hypertension and cardiovascular diseases. PVDF flexible pressure sensors possess the characteristics of high sensitivity, good flexibility, and strong biocompatibility, thereby demonstrating extensive application potential in areas such as health monitoring, wearable devices, and electronic skins. This paper focuses on the development of a modified piezoelectric polymer and its application in an intelligent blood pressure monitoring system, demonstrating its outstanding performance and feasibility through a series of experiments. This research provides innovative material choices for the development of intelligent medical devices and offers beneficial guidance for the design and application of future intelligent health monitoring systems.
... The monitoring system has been tested under various conditions, which provides a prerequisite for wide applications in daily health monitoring. Another interesting study on the use of a PVDF polymer was published by Lei et al. [38]. In this study, a piezoelectric PVDF film encapsulated in polydimethylsiloxane was used. ...
This article explores the importance of wearable and remote technologies in healthcare. The focus highlights its potential in continuous monitoring, examines the specificity of the issue, and offers a view of proactive healthcare. Our research describes a wide range of device types and scientific methodologies, starting from traditional chest belts to their modern alternatives and cutting-edge bioamplifiers that distinguish breathing from chest impedance variations. We also investigated innovative technologies such as the monitoring of thorax micromovements based on the principles of seismocardiography, ballistocardiography, remote camera recordings, deployment of integrated optical fibers, or extraction of respiration from cardiovascular variables. Our review is extended to include acoustic methods and breath and blood gas analysis, providing a comprehensive overview of different approaches to respiratory monitoring. The topic of monitoring respiration with wearable and remote electronics is currently the center of attention of researchers, which is also reflected by the growing number of publications. In our manuscript, we offer an overview of the most interesting ones.
... In terms of signal acquisition, vibration-based sensors are major devices for BCG signals acquisition. In recent years, piezoelectric film, such as polyvinylidene fluoride (PVDF), has emerged as an ideal material for manufacturing sensors due to its thinness, flexibility, and low cost [5], and has been widely used in physiological signal detection devices [6]. These sensors convert BCG signals into electrical signals and extract heart rate information from the signals through certain algorithms. ...
Ballistocardiogram (BCG) is a non-invasive physiological signal detection method that can be used for non-contact detection of resting heart rate (RHR) and has been widely used in human health monitoring. However, the BCG signal is vulnerable to noise, making it challenging to accurately measure heart rate. In this paper, we propose a noise reduction model for the BCG signal based on Gramian Angular Field (GAF) and an improved Denoising Autoencoder (DAE), referred to as the GDAE model, to accurately detect heart rate in noise-contaminated signals. First, the Gramian Angular Field transform is used to convert the one-dimensional BCG signal into two-dimensional image information, highlighting the difference between the signal centroid information and noise information; after that, the transformed image is denoised by the Denoising Autoencoder to obtain a denoised BCG signal. After noise reduction, the heart rate of the subject is calculated using the adaptive template matching method. The test proves that under the strong noise interference, the proposed method improves the recall by 6.87% and the accuracy by 6.02% compared with the traditional method, indicating a better detection effect. Furthermore, the comparison test shows that the GDAE model has a significant noise reduction effect on the BCG signal, which improves the practicality of the BCG method for heart rate detection.
... 26 In medicine, PVDF has been widely exploited 27 for tissue engineering, 28 drug delivery, 29 the fabrication of antibacterial membranes 30 and the manufacturing of biosensors. [31][32][33] In relation to LIS systems, its fluorinated chemical nature allows for stable interactions with fluorinated lubricants without the need for further modification of surface chemistry. ...
Thrombus formation and infections caused by bacterial adhesion are the most common causes of failure in blood-contacting medical devices. Reducing interaction of pathogens by using repellent surfaces has proven to be a successful strategy in preventing device failure. However, designing scale-up methodologies to create large scale repellent surfaces remains challenging. To address this need, we have created an all-polymeric lubricant-infused system using an industrially viable swelling-coagulation solvent (S-C) method. This induces hierarchically structured micro/nano features onto the surface, enabling improved lubricant-infusion. Poly(3,3,3 - trifluoropropylmethylsiloxane) (PTFS) was used as the lubricant of choice, a previously unexplored omniphobic non-volatile silicone oil. This resulted in all-polymeric liquid-infused surfaces that are transparent and flexible with long-term stability. Repellent properties have been demonstrated using human whole blood and methicillin-resistant Staphyloccus aureus (MRSA) bacteria matrices, with lubricated surfaces showing 93% reduction in blood stains and 96.7% reduction in bacterial adherence. The developed material has the potential to prevent blood and pathogenic contamination for a range of biomedical devices within healthcare settings.
... Sensors using polyvinylidene fluoride (PVDF), a popular piezoelectric material, have been proven to be effective in detecting vital signals. Many studies have proven that PVDF is very effective in measuring the biological signals of the human body [3][4][5][6] . Using PVDF, an equipment that can be used at home was developed. ...
Cardiovascular and deep breathing diseases can be detected by measuring human signals such as heart rate, respiration, and blood pressure, which are important physiological parameters for accessing the state of the body. However, conventionally, heart and respiration rates are monitored using different sensors, which is cumbersome and can further increase the psychological burden on patients. To address these issues, this report proposes a sensor consisting of two stacked elements that can simultaneously measure heart and respiration rates. The two signals received can be expressed separately as heart and respiration rates after signal processing. The two stacked elements are composed of polyvinylidene fluoride thin film bonded to a polydimethylsiloxane substrate. One element (element 1) measures movement related to the heart, and the other (element 2) measures movement related to breathing. Elements 1 and 2 were experimentally observed to have sensitivities of 0.163 V/N and 0.209 V/N, respectively. In addition, the proposed system was compared with a commercial digital heart rate and respiration rate measurement instrument and was verified to be effective for simultaneous measurement of human vital signals with multiple sensors. In addition, the proposed system is flexible, lightweight, and inexpensive, making it convenient and economical.
... Wearable and skin-attachable piezoelectric pressure sensors (PPSs), which convert mechanical energy into electrical energy (especially voltage), offer several benefits in personal healthcare and safety systems, such as sensitive response to stress/strain, self-powered, low-cost, easily-expandable, portable, and secure properties. Therefore, PPSs have been developed for the detection of physical and physiological signals such as blood pressure [1][2][3][4][5] , respiration [6,7] , muscle motion [8,9] , heart rate [4,10,11] , joint motion [12][13][14][15] , and so on. Various piezoelectric materials, including lead zirconate titanate (Pb[Zr x Ti 1-x ]O 3 , PZT) [3] , zinc oxide (ZnO) [16,17] , barium titanate (BaTiO 3 , BTO) [8,18] , polyvinylidene fluoride (PVDF) [6,19] , and single-crystalline Group-IIInitrides (III-Ns) [10,20] , have been employed for the development of PPSs. ...
... Therefore, PPSs have been developed for the detection of physical and physiological signals such as blood pressure [1][2][3][4][5] , respiration [6,7] , muscle motion [8,9] , heart rate [4,10,11] , joint motion [12][13][14][15] , and so on. Various piezoelectric materials, including lead zirconate titanate (Pb[Zr x Ti 1-x ]O 3 , PZT) [3] , zinc oxide (ZnO) [16,17] , barium titanate (BaTiO 3 , BTO) [8,18] , polyvinylidene fluoride (PVDF) [6,19] , and single-crystalline Group-IIInitrides (III-Ns) [10,20] , have been employed for the development of PPSs. Among them, PZT has been most widely adopted due to its excellent piezoelectric properties. ...
Whereas piezoelectric pressure sensors (PPSs) have been applied in the monitoring of human body movement and physiological parameters, they show inherent limitations in wearable applications, including toxicity, degradation, and brittleness. In this study, we develop safe, stable, and mechanically flexible composite thin films consisting of polyvinylidene fluoride (PVDF), BaTiO3 nanoparticles (BTO-NPs), and textured aluminum nitride (AlN) thin film for the demonstration of wearable PPS with enhanced output performance and biocompatibility. The PPS made of BTO-NP-embedded-PVDF and AlN film on Cu foil is attached to different parts of human body to measure different output voltages depending on the physiological and physical stimulus. The simple bending (from breathing, chewing, and swallowing), joint motions (at wrist, elbow, and finger), and low- (from eyeball movement) and high-pressure applications (by squat, lunge, and walking) are measured. Our PVDF+BTO-NP/AlN-PPS (PBA-PPS) device has the potential for personal safety, healthcare, and activity monitoring applications with easy wearability.
... PVDF has also gained interest in the medical field and is used more frequently for measuring the respiratory airflow and respiratory effort [4]. The RIP (Respiratory Inductance Plethysmography) belts have been widely used these days for respiratory effort monitoring. ...
Polyvinylidene fluoride (PVDF) is known as a favorite polymer from the family of fluoropolymers due to its excellent piezoelectric properties, thermal stability, and mechanical strength. It has a good processability, and it also possess chemical resistance property to different materials such as different acids, bases, organic solvents, oil, and fat. The present study reveals an overview of the recent growth and development in the application perspective and modification of PVDF membranes, majorly focus on sensors and actuators, spin-valve devices, magnetoelectric materials, energy harvesting applications, tissue engineering, modeling engineering, and other biomedical engineering and devices. From an electronic point of view, ferroelectric polymers are insulating, polar, and possess a non-conjugated backbone; therefore, they are termed as highly insulating materials. The insulating polymers are most attractive for the study of charge transportation and storage. Such polymers also yield the best electrets for practical application because of their insulating properties and high concentration of deep trapping sites. Thus, the objective of this review is to present the physical, chemical, thermal, and mechanical properties of PVDF. This article also provides an intelligent direction in the progress of PVDF in different fields of science and technology.
Graphical abstract
... Li Tao (Lu et al., 2018) designed a four-sided desktop humanoid manipulator that can effectively analyse three dimensional tactile signals by using PVDF piezoelectric film as a tactile sensor. Lei et al. (2015) studied a PVDF sensor patch for respiratory detection in dynamic walking conditions. Using inverse piezoelectric effect of PVDF, Suaste-Gómez et al. (2016) made a PVDF bionic ear been used as a hearing aid. ...
... Li Tao (Lu et al., 2018) designed a four-sided desktop humanoid manipulator that can effectively analyse three dimensional tactile signals by using PVDF piezoelectric film as a tactile sensor. Lei et al. (2015) studied a PVDF sensor patch for respiratory detection in dynamic walking conditions. Using inverse piezoelectric effect of PVDF, Suaste-Gómez et al. (2016) made a PVDF bionic ear been used as a hearing aid. ...
... Lei et al. proposed a small size, light weight, easy to use, low cost, and portable PVDF-based sensor patch for respiration detections in both static (sitting) and dynamic (walking) condition. The sensor patch produced electrical signals from the periodical deformations for the human chest during the respiratory movements, see Figure 9 (b) (Lei et al., 2015). Pressure sensors can be also applied near to the mouth or nose area to detect the flow of breath with high accuracy (Yaghouby et al., 2016). ...
Wearable electronics are becoming increasingly important for medical applications as they have revolutionized the way physiological parameters are monitored. Ferroelectric materials show spontaneous polarization below the Curie temperature, which changes with electric field, temperature and mechanical deformation. Therefore, they have been widely used in sensor and actuator applications. In addition, these materials can be used for conversion of human-body energy into electricity for powering wearable electronics. In this paper, we review the recent advances in flexible ferroelectric materials for wearable human energy harvesting and sensing. To meet the performance requirements for medical applications, the most suitable materials and manufacturing techniques are reviewed. The approaches used to enhance performance and achieve long-term sustainability and multi-functionality by integrating other active sensing mechanisms (e.g. triboelectric and piezoresistive effects) are discussed. Data processing and transmission as well as the contribution of wearable piezoelectric devices in early disease detection and monitoring vital signs are reviewed.
