Two-Dimensional Nanomaterial-Based Flexible Sensors for Blood Pressure Monitoring: History
View Latest Version
Please note this is an old version of this entry, which may differ significantly from the current revision.
Contributor:
Siti Nor Ashikin Ismail
,
Nazrul Anuar Nayan
,
Muhammad Aniq Shazni Mohammad Haniff
,
Rosmina Jaafar
,
Zazilah May

Flexible sensors have been extensively employed in wearable technologies for physiological monitoring given the technological advancement in recent years. Conventional sensors made of silicon or glass substrates may be limited by their rigid structures, bulkiness, and incapability for continuous monitoring of vital signs, such as blood pressure (BP). Two-dimensional (2D) nanomaterials have received considerable attention in fabrication of flexible sensors due to their large surface area-to-volume ratio, high electrical conductivity, cost-effectiveness, flexibility, and lightweight.

  • flexible
  • sensors
  • blood pressure
  • 2D nanomaterials
  • wearable

1. Introduction

Physiological monitoring offers deep understanding to evaluate the health state of an individual [1]. In recent years, several attempts have been made to modify existing sensors for developing wearable point-of-care systems that are suitable for personalized health monitoring [2][3]. The widespread use of wearable sensors in healthcare have heightened the need for non-invasive, continuous, and real-time monitoring of vital signs, such as blood pressure (BP). Wearable technologies play a significant role in improving human life quality through accurate disease prediction, timely treatment, reduced medical burden, and improved longevity [4][5][6][7][8]. A rapid development of wearable devices has occurred since a decade ago; these devices are not limited to smartwatches [9] and fitness bands [10], and other sensing devices, such as skin patches [11][12][13] and electronic tattoos (e-tattoo) [14][15][16], are gaining increased research attention because they are more appealing to users. Previous works demonstrated how flexible sensors enable a wide pressure detection range [17][18][19].
The advent of flexible materials has led to the plethora of studies on two-dimensional (2D) nanomaterials as promising candidates for the development of sensing elements in flexible sensors. The extensive exploitation of these materials, particularly since the successful exploration of graphene (Gr) by Novoselov et al. [20] in 2004, has inspired the discovery of other similar sheet-like structures, such as transition metal dichalcogenides (TMDs) and transition metal carbides and nitrides (MXenes).
In contrast to other candidates, such as silver (Ag) and copper (Cu), 2D nanomaterials have a number of attractive features, such as larger surface-area-to-volume ratio, higher electrical conductivity, cost effectiveness, flexibility, and lighter weight [21][22][23][24][25][26][27], which confer sensors with excellent wearable sensing performance. Further, conventional sensors are mainly fabricated based on silicone (Si) or glass substrates, making them rigid, bulky, and incapable for physiological monitoring [28][29][30], which in turn degrade the sensor performance. The two tools currently used for BP measurement are the arterial catheter and the sphygmomanometer. The former is the gold standard in BP monitoring and mainly employed to measure continuous and accurate BP readings of critical patients [31]. A major problem of this modality is that patients often feel pain from invasive catheter insertion [32] and trained personnel are required to perform the measurement [33]. The latter is non-invasive, more practical, and has expanded usability outside clinical settings. Although various cuff-based BP monitors are available on the market, their use has been associated with certain drawbacks, such as intermittent measurements, calibration issues, motion sensitivity, and whitecoat effect [34][35][36][37], leading to inaccurate detection. Current studies show an increasing trend of developing non-invasive and cuffless BP sensors by using photoplethysmogram and electrocardiogram (ECG); however, these techniques are prone to produce motion artifacts, BP variations across devices, and shallow penetration depth into the deep artery [38][39][40].
The continuous development of 2D wearable nanomaterial-based technologies is needed to overcome the aforementioned challenges and offer a non-invasive and continuous BP monitoring system with great skin conformability, biocompatibility, improved efficiency, and accurate results.

2. Transduction Mechanisms

2.1. Piezoelectric Mechanism

The piezoelectric effect was discovered by the Curie brothers in 1880 [41]. The study of piezoelectric has grown significantly since the employment of quartz crystals in sonar [42]. It was then replaced by inorganic piezoelectric materials, such as barium titanate and lead zirconate titanate (PZT), which exhibit distinguished piezoelectric characteristics [43].
Piezoelectric sensor is based on electrical signals generated when deformation occurs on non-centrosymmetric materials. When these materials experience stress, the crystal structure becomes dislocated, causing the accumulation of positive and negative charges across the faces. As a result, net polarization is formed throughout the crystal structure. Significant potential difference is observed when current is applied to the sensing system.
The advantage of using a piezoelectric sensor is that it can measure dynamic signals. Moreover, it performs best in terms of sensitivity, fast response time, and low power consumption. The piezoelectric behavior of 2D nanomaterials has gained considerable interest since it was reported in 2014 [44]. However, the main disadvantages of this sensor are its inability to monitor static signals, low sensitivity for detection of low pressure, and use of extremely harmful lead-based materials.

2.2. Capacitive Mechanism

The capacitive effect of an Si-based sensor was first studied by Michael Faraday in 1831 [45]. The capacitive transduction mechanism differs from piezoelectric and piezoresistive mechanisms in that no pressure is applied to introduce deformation, but it instead involves the contact between two plates. The parallel-plate capacitor is a typical arrangement of a capacitive sensor, wherein two plates are separated from each other by a dielectric layer. A Si-based organic polymer known as polydimethylsilixone (PDMS) has been widely investigated as a dielectric layer in capacitive sensors due to its great flexibility, biocompatibility, and low toxicity [46][47]. A reduction in separation distance between plates leads to a change in capacitance [48].

Capacitive sensor has a number of advantages over piezoelectric-based sensor in terms of lower power consumption, wider detection range, and higher sensitivity for detection of low pressure. However, this sensor has slow response time, expensive fabrication procedure, and power source dependency. 

2.3. Piezoresistive Mechanism

The piezoresistive effect is not a recent discovery, given that its first experimental demonstration was carried out in 1954 by Smith [49]. The resistivity of a material was identified as the main factor contributing to the change in resistance [50]. The contact area of dielectric materials is expanded by imposing mechanical stimulation, thus allowing the formation of more conductive channels [51]. This phenomenon changes the material resistivity and causes variations in electrical signals [52]. Gr and carbon nanotubes are frequently exploited in the development of piezoresistive flexible sensors. When the applied stress is removed, the resistance returns to its original state.

The piezoresistive effect has been widely investigated and used in a broad range of fields, such as microelectromechanical systems. Various piezoresistive flexible sensors have been proposed to monitor the physiology of an individual owing to its ease of fabrication, simplicity in structure, cost-effectiveness, capability for detection of static and dynamic signals, low power consumption, biocompatibility, and wide pressure-sensing range. However, this type of sensor suffers from low sensitivity for detection of low pressure and power source dependency.

2.4. Triboelectric Mechanism

The discovery of the triboelectric effect began to emerge about 2600 years ago [53]. This effect involves the generation of electrical signals as a result of the surface contact between two triboelectric materials. When these materials are in contact with each other, charges will overlap and align according to polarity across the surface. When the applied stress is slowly removed, the contact electrification of the materials reduces, and a potential difference can be measured as a result of electrostatic induction. This phenomenon allows the charges to flow until a net equilibrium is achieved, thereby generating electrical signals [54]. The development of triboelectric nanogenerators in 2012 is one of the first studies that explored the triboelectric effect in sensors [55].

Triboelectric sensor exhibits excellent properties for wearable applications, particularly physiological monitoring, due to its ability to self-power and detect dynamic signals, lightweight, and low fabrication cost. However, when this sensor is employed to monitor the vital signs of individuals, several issues, such as biocompatibility, biodegradability, and short service lifetime, occur.

Therefore, identifying the type of vital signs being monitored is crucial prior to the fabrication of flexible sensors. For instance, sensors developed in the form of patches are more suitable for continuous BP monitoring because they exhibit greater flexibility on the skin and comfortable for long wear. Piezoresistive sensor has attracted much research attention in the field of health monitoring system through wearable flexible sensors due to advantages including dynamic sensing, low cost and power consumption, and biocompatibility.

3. Sensing Performance Parameters

Sensing performance is another significant aspect of developing wearable flexible sensors. Several key performance parameters of sensors are discussed. Sensitivity, or gauge factor (GF), defines the minimum input that is needed to create changes in electrical signals as a response to mechanical stimuli [56]. Limit of detection (LOD) describes the lowest pressure that can be detected by the sensor to generate electrical signals at the ground pressure of 0 Pa [57]. Response time is the time taken by a sensor to produce detectable changes in electrical signals in response to stress [44].
The stretchability of a sensor refers to its ability to retain internal conductive network connection and resist permanent deformation under external stress [58]. A sensor should maintain a trade-off between high sensitivity and good stretchability to ensure that the original device structure is maintained without neglecting subtle pressure detection under applied stress [59]. Linearity refers to the direct proportional relationship between electrical signals and mechanical stimuli within the set range limits. This parameter is represented by the coefficient of determination (R2), whereby the parameters are considered to achieve good linearity when the R2 value reaches 1 [52]. Detection range indicates the minimum and maximum pressure values that can be detected by the sensor.
These parameters should be considered during the device engineering phase to develop a flexible sensor for monitoring BP continuously and with great accuracy. High sensitivity, low LOD, fast response time, excellent stretchability, good linearity, and broad detection range are some of the desirable properties to realize wearable BP monitoring systems for future personalized medicine.

4. Two-Dimensional Nanomaterials for Flexible Sensors

4.1. Graphene (Gr)

Gr is a class of 2D nanomaterials known as an allotrope of carbon and arranged in a hexagonal lattice structure [60][61][62]. Gr is a zero-band gap material with exceptional characteristics such as being ultrathin, light weight, and stronger than steel, and having high electron mobility [63][64][65]. Pristine Gr has the least crystalline defect, high purity, and thermal conductivity. Gr and its derivatives are in huge demand in multiple fields [66], such as in coatings [67], biosensors [68], batteries [69], and membranes [70]. Several attempts were conducted to modify the morphology of pristine Gr to tailor its practical applications through bandgap engineering [71].

Due et al. [72] successfully fabricated a wearable piezoresistive sensor by facile preparation methods. Gr was grown on a non-woven fabric (GNWF) substrate to produce a wearable sensor that is compatible with cloth. The sensor had excellent sensitivity of around 0.057 kPa-1 and GF of -7.1 at the applied strain of 1% for 10,000 cycles. Ai et al. [73] demonstrated a piezoresistive sensor based on reduced-graphene-oxide (rGO) sandwiched in between PDMS films. This sensor was tested on a healthy subject and successfully detected pulse waveform, including the diastolic tail in which tonometry method failed to sense. The results showed that this flexible sensor can be further extended into health wearables to monitor BP continuous with 50.9 kPa-1 sensitivity, 3 Pa LOD, ~1 µW power consumption, 50 ms response time, and high durability. Luo et al. [74] presented a piezocapacitive sensor that was micro-fabricated with graphene nanowalls (GNW), PDMS, and zinc oxide (ZnO) to monitor pulse for wearable applications. The proposed technique exhibited improved sensing performance with 22.3 kPa-1 sensitivity, 25 ms response time, and 22 kPa sensing range. Wu et al. [75] developed a Gr-based piezoresistive sensor by using laser scribing method for monitoring BP. The sensor showed an average sensitivity of 12.3 kPa-1 and enabled different BP measurement locations, which is advantageous for non-invasive monitoring,

Gr has the disadvantages of high fabrication cost and lack of well-established synthesis methodologies, contributing to the challenging preparation of monolayer with excellent quality, controllable thickness, and mass-produced Gr [76]. Albeit the continuous switching behavior of Gr, making it difficult for energy-storage devices, this problem can be addressed by opening the bandgap with regard to the favorable on–off switching properties.

4.2. Transition Metal Dichalcogenides (TMD)

The discovery of other 2D nanomaterials has become more popular since the successful findings in 2004. TMDs have gained increased attention for 2D nanomaterials because their crystal structures are similar to those of graphite. The acronym of TMDs is derived from MX2, where M describes the transition metal from groups 4 to 11, such as molybdenum (Mo) and stannum (Sn). Meanwhile, X represents the elements of group 16, such as sulfur (S) and selenium (Se), which are known as chalcogens [65]. The heterostructure engineering of TMDs is possible due to their weak van der Waals interlayer interaction and easily tunable bandgap, which are not found in Gr [77][78]. TMDs exhibit good electronic and optical properties and are suitable for biosensors [79], light-emitting diodes [80], and memory devices [81]. Besides the widely used Gr, progress has been achieved in developing flexible sensors based on TMDs for designing biomedical devices.

For instance, Qiu et al. [82] proposed a piezoelectric MoS2 sensor by forming conductive networks between MoS2 nanosheets and Ag nanofibers in an elastic conductive film. The developed sensor possessed significant potential as health wearables due to its ability to detect systolic and diastolic peaks, sensitivity of 3, 3000, 0–13% strain range, and relatively fast response of ∼850 ms for stretching and relaxation time. Furthermore, Tannarana et al. [83] reported a wearable multimodal sensor developed from SnSe2 nanosheets grown on paper substrate through liquid-phase exfoliation. The sensor exhibited excellent sensing performance with 868% responsivity, 1.79 kPa-1, 100 ms response time, 2–100 kPa detection range, and 5, 000 cycles of loading pressure. Moreover, Pataniya et al. [84] manufactured a flexible piezoresistive sensor based on MoS2 nanosheets by using a cellulose paper as substrate. The sensor had high sensitivity of 18.42 kPa-1 for low-pressure range, sensing range of 0.001–0.5 kPa, and fast response time. The time difference between systolic and diastolic peaks measured was 260 ms, which is in agreement with previous studies.

TMDs have shown potential for flexible sensors to monitor vital signs; however, the current synthesis techniques are yet scalable and reliable for producing monolayers that are defect free and have controllable thickness and excellent quality [85][86][87].

4.3. Transition Metal Carbides and Nitrides (MXene)

Gogotsi and his team [88] conducted the first experiment on MXenes in 2011 by using hydrofluoric acid (HF) to exfoliate three-dimensional titanium aluminum (Al) carbide (Mn+1AlXn) and produce layers of 2D titanium carbide (Mn+1XnTx). M represents transition metals, such as Mo, titanium (Ti), and niobium (Nb); X denotes carbon/nitrogen; and T refers to functional termination groups, such as hydroxyl (-OH), fluorine (-F), and oxygen (-O) [89]. As the name reflects the elements, these materials comprise multi-layers of transition metal carbides, nitrides, and carbonitrides [90]. Recently, MXene has been found to be an ideal candidate for a wide range of applications, such as batteries [91], conductive fillers [92], supercapacitors [93], and solar cells [94].
A growing trend on the development of MXenes-based wearable sensors has occurred due to their superior electrical conductivity, peculiar multilayer structure, and large surface-area-to-volume ratio [95]. For instance, the abundant functional termination groups and the hydrophilic surface in MXenes’ nanostructures confer them with great capability to mix with polymers. The interlayer spacing in between MXene multilayers and the hybridization with polymers in flexible devices would significantly enhance sensor performance including enhanced sensitivity and greater electrical conductivity [96][97].

A novel flexible piezoresistive sensor based on Ti3C2Tx/PDMS developed by Cheng et al. [98] using simple abrasive paper stencil printing to detect the pulse wave of an individual. The sensor detected three important peaks of pulse waveform and achieved sensitivity of 151.4 kPa-1, response time of <130 ms, and LOD of 4.4 Pa. The sensor’s response showed high competency in continuous health monitoring. Li et al. [99] developed Ti3C2Tx flexible piezoresistive sensor on poly (vinylidene fluoride) trifluoroethylene (P(VDF-TrFE)) substrate by spin coating. The prepared sensor successfully detected the pulse wave peaks and exhibited excellent properties, with 817.4 kPa-1 sensitivity, 16 ms response time, and 0.072–0.74 Pa detection range. Su et al. [100] fabricated a flexible piezoresistive sensor based on Ti3C2Tx by using honeycomb approach on PDMS conductive film. The sensor had sensitivity of 0.61 kPa-1, response time of 160 ms, and detection range of 0–50 kPa. Not only that, radial pulse waveforms were detected in real-time using this sensor.

Although Mxene can be regarded as an ideal candidate for flexible sensing application, it has several disadvantages that can affect its long-term stability. MXene films have greater tendency to experience fracture due to poor mechanical properties caused by the weak van der Waals interaction in MXene nanosheets [101][102]. Moreover, the exfoliation of the Al layer from the MAX phase by using HF etchant may introduce nanosheet restacking, leading to easy oxidation in the ambient environment and reduced biocompatibility [103].

In summary, 2D nanomaterials exhibit potential as functional materials in flexible sensors due to their large surface area-to-volume ratio, which leads to high sensitivity, fast response time, and wide detection range. Although a number of studies have reported on flexible sensors utilizing these nanomaterials, well-grounded conceptual and methodological approaches for continuous BP monitoring are lacking. Majority of these studies on wearable applications have focused only on human activity detection. Few studies have attempted to validate the BP readings obtained from the proposed sensors with those from a commercial cuff sphygmomanometer. 

5. Wearable Blood Pressure Monitoring

BP is an essential vital sign in human health monitoring, and its complex dynamics make it difficult to understand. Based on the American Heart Association, the normal systolic BP (SBP) and diastolic BP (DBP) of healthy people are ≤120 and 80 mmHg, respectively [104]. Individuals with BP readings beyond the normal range are considered as hypertensive [105], while those with readings lower than the baseline are considered normotensive [106]. A BP pulse waveform consists of three main peaks, namely, percussion wave (P wave), tidal wave (T wave), and diastolic wave (D wave). In general, P wave is the early SBP, T wave is the late SBP, and D wave is the DBP [107].
Arterial catheterization is the gold standard for continuous measurement of BP, yet it is invasive and widely employed only on critically ill patients. Meanwhile, sphygmomanometers can monitor BP unobtrusively but suffer from several limitations, such as intermittent readings and non-portability. In this regard, wearable flexible sensors are expected to pave new routes toward remote health monitoring as the future of telemedicine. 
Noh et al. [72] integrated four components, namely, ECG, ballistocardiogram (BCG), flexible electronic circuits, and a ferroelectric film, in a sensing platform. Silver paste was used to sandwich the ferroelectric layer in between the ECG and BCG through a screen-printing method. Three healthy subjects were selected to participate in the study. Simultaneous measurements were conducted using the developed sensor and a reference device, Finapres. The sensor showed comparable SBP values from both devices with the mean error and standard deviation of −0.16 and 4.12 mmHg, respectively. Although this work did not measure DBP, the results were promising and proved the feasibility of a flexible BP patch as an alternative to the current sphygmomanometer for continuous BP monitoring.

Dagdeviren et al. [108] fabricated a piezoelectric pressure sensor by using PZT and Si substrate for long-term BP monitoring. Here, the design of the sensor played a significant role as the PZT is more susceptible to the deformation than the Si substrate, allowing the sensor to be skin-mounted. The average SBP and DBP readings of three volunteers recorded using this device are in agreement with the cuff BP values, with averages of 110 and 65 mmHg for SBP and DBP, respectively. The sensor can stretch up to 30% of its size and has 0.1 ms response time, 25 µm thickness, and 0.005 Pa LOD. The developed sensor can be beneficial for continuous monitoring of human health. Luo et al. [109] documented a skin patch that can monitor continuous BP non-invasively. The sensing mechanism is based on the piezoresistive properties of carbon-made textile and epidermal ECG sensors. Compared with the cuff BP monitor, the fabricated sensor had small deviations of 6.5 ± 4.9 and -0.4 ± 3.9 mmHg for SBP and DBP, respectively, as well as low power consumption of 3 nW. Hence, the sensor has potential to be integrated in health wearables.

Wang et al. [110] reported an ultrasonic wearable sensor for continuous monitoring BP. Piezoelectric composites and thin Si layer were used as the sensing element and elastomer, respectively. Ultrasonic waves were employed to provide deeper penetration for BP detection. The proposed sensor had remarkable results and exhibited superior properties over tonometry modality for long-term monitoring of BP with up to 60% stretchability, 23.6 mW power consumption, and ~5 Pa loading pressure on the skin. Sempionatto et al. [111] extended the work by Wang et al. by developing ultrasonic electrochemical sensors based on PZT and printed polymer composites for monitoring BP and other physiological parameters, such as heart rate (HR), glucose, and lactate. Participants were given different stimuli, including food and drink, as well as physical activities, before and after measurement of the parameters. The developed epidermal sensor exhibited satisfactory performance when validated with cuff BP readings, thus demonstrating its suitability as a multimodal sensing device for wearable BP application.

Laurila et al. [112] proposed inkjet and blade coating fabrication methods for developing an e-tattoo sensor with piezoelectric properties. The fabricated device is the thinnest fully printed piezoelectric sensor with 4.2 µm thickness. The sensor showed improved sensitivity of ~50 times than the reference BP monitor that exploits the arterial tonometry principle. The biomedical company Vivalink introduced the first commercial multi-sensing patch to monitor BP continuously and remotely [130]. The sensor detected various vital signs such as SBP, DBP, and HR with the universal regulatory clearance. This technology features small design, wireless connection, real-time monitoring, and water resistance.

Long-term remote BP monitoring is feasible and relatively accurate with the emergence of advanced technologies and 2D nanomaterials. The ground-breaking research efforts are significant for the early diagnosis and prognosis of health complications such as cardiovascular diseases (CVD). The detection of CVD continues to be a challenge for physicians, and late-stage diagnosis often leads to stroke incidence and mortality. Continuous BP monitoring using wearables, such as epidermal patches and e-tattoos, enables timely treatment for high-risk patients, particularly those with hypertension as it is an underlying risk factor of CVD. This monitoring system is expected to facilitate real-time BP monitoring through automated notification of abnormal BP readings, triaging perioperative patients, and mitigating motion artifacts in other cuffless BP monitors.

6. Challenges and Future Outlooks

Despite the successful development of laboratory-based cuffless sensors for continuous BP monitoring, further improvements are required to address their limitations prior to reaching market readiness and clinical acceptability. Thus far, the synthesis of 2D nanomaterials remains a major challenge in wearable sensing implementation. Current techniques suffer from weaknesses that hinder their abilities to fabricate a high quality and zero-defect sensing layer. To address this issue, scholars should develop new surface modification techniques with the benefits of low fabrication cost and mass production of 2D nanomaterials.

Another key challenge for the implementation of wearable is biodegradability, which is a growing health concern worldwide. For instance, the use of toxic chemicals, such as HF acid, to produce 2D nanomaterials can cause adverse effects on the environment and humans through release of chemical wastes and emission of poisonous gases. Therefore, continuous research efforts are needed to fabricate wearable sensors based on 2D nanomaterials that contain non-harmful by-products and are safe for humans.

Monitoring of BP is technically challenging because it involves manual handling task. In the future, the potential use of artificial intelligence (AI) should be explored because it is at the forefront of smart wearables for continuous physiological monitoring. Aspects that should be investigated are the integration of machine learning, as a subset of AI, to enhance the performance of wearable sensors through the prediction of vital signs, generation of precise outputs, real-time monitoring and seamless transmission of signals.

Despite the potential of 2D nanomaterials in flexible sensors, their commercial applications to wearable BP devices are still far from being achieved. One of the challenges is the stability of 2D nanomaterials when integrated into wearable technologies, leading to difficulty in large-scale production. This problem has inspired researchers to work on wearables with improved sensor performance through available and emerging techniques.

This entry is adapted from the peer-reviewed paper 10.3390/nano13050852

References

  1. Wu, W.; Haick, H. Materials and wearable devices for autonomous monitoring of physiological markers. Adv. Mat. 2018, 30, e1705024.
  2. Wang, X.; Liu, Z.; Zhang, T. Flexible sensing electronics for wearable/attachable health monitoring. Small 2017, 13, 1602790.
  3. Guk, K.; Han, G.; Lim, J.; Jeong, K.; Kang, T.; Lim, E.-K.; Jung, J. Evolution of wearable devices with real-time disease monitoring for personalized healthcare. Nanomaterials 2019, 9, 813.
  4. Tolba, A.; Said, O.; Al-Makhadmeh, Z. MDS: Multi-level decision system for patient behavior analysis based on wearable device information. Comput. Commun. 2019, 147, 180–187.
  5. Jalal, A.; Batool, M.; Kim, K. Stochastic recognition of physical activity and healthcare using tri-axial inertial wearable sensors. Appl. Sci. 2020, 10, 7122.
  6. Tang, N.; Zheng, Y.; Cui, D.; Haick, H. Multifunctional dressing for wound diagnosis and rehabilitation. Adv. Healthc. Mater. 2021, 10, 2101292.
  7. Durán-Vega, L.A.; Santana-Mancilla, P.C.; Buenrostro-Mariscal, R.; Contreras-Castillo, J.; Anido-Rifón, L.E.; García-Ruiz, M.A.; Montesinos-López, O.A.; Estrada-González, F. An IoT system for remote health monitoring in elderly adults through a wearable device and mobile application. Geriatrics 2019, 4, 34.
  8. Ahmad, W.N.W.; Adib, M.A.H.M.; Ahmad, Z.; Zaihidee, F.M.; Txi, M.R.S. Integration of the Health Monitoring System with IoT Application in Sports Technology: A Review. J. Kejuruter. 2022, 5, 101–109.
  9. Wen, D.; Zhang, X.; Liu, X.; Lei, J. Evaluating the consistency of current mainstream wearable devices in health monitoring: A comparison under free-living conditions. J. Med. Internet Res. 2017, 19, e68.
  10. Haghayegh, S.; Khoshnevis, S.; Smolensky, M.H.; Diller, K.R.; Castriotta, R.J. Accuracy of wristband fitbit models in assessing sleep: Systematic review and meta-analysis. J. Med. Internet Res. 2019, 21, e16273.
  11. Lee, Y.; Chung, J.W.; Lee, G.H.; Kang, H.; Kim, J.-Y.; Bae, C.; Yoo, H.; Jeong, S.; Cho, H.; Kang, S.-G.; et al. Standalone real-time health monitoring patch based on a stretchable organic optoelectronic system. Sci. Adv. 2021, 7, eabg9180.
  12. Leal, C.; Lopes, P.A.; Serra, A.; Coelho, J.F.J.; de Almeida, A.T.; Tavakoli, M. Untethered disposable health monitoring electronic patches with an integrated Ag2O−Zn battery, a AgInGa current collector, and hydrogel electrodes. ACS Appl. Mater. Interfaces 2020, 12, 3407–3414.
  13. Nakata, S.; Arie, T.; Akita, S.; Takei, K. Wearable, flexible, and multifunctional healthcare device with an ISFET Chemical sensor for simultaneous sweat pH and skin temperature monitoring. ACS Sens. 2017, 2, 443–448.
  14. Chen, Y.; Zhou, G.; Yuan, X.; Li, C.; Liu, L.; You, H. Substrate-free, ultra-conformable PEDOT: PSS E-tattoo achieved by energy regulation on skin. Biosens. Bioelectron. 2022, 206, 114118.
  15. Laurila, M.M.; Peltokangas, M.; Montero, K.L.; Verho, J.; Haapala, M.; Oksala, N.; Vehkaoja, A.; Mäntysalo, M. Self-powered, high sensitivity printed e-tattoo sensor for unobtrusive arterial pulse wave monitoring. Nano Energy 2022, 102, 107625.
  16. Wang, Y.; Qiu, Y.; Ameri, S.K.; Jang, H.; Dai, Z.; Huang, Y.A.; Lu, N. Low-cost, μm-thick, tape-free electronic tattoo sensors with minimized motion and sweat artifacts. NPJ Flex. Electron. 2018, 2, 6.
  17. Doshi, S.M.; Thostenson, E.T. Thin and flexible carbon nanotube-based pressure sensors with ultrawide sensing range. ACS Sens. 2018, 3, 1276–1282.
  18. Zhong, M.; Zhang, L.; Liu, X.; Zhou, Y.; Zhang, M.; Wang, Y.; Yang, L.; Wei, D. Wide linear range and highly sensitive flexible pressure sensor based on multistage sensing process for health monitoring and human-machine interfaces. J. Chem. Eng. 2021, 412, 128649.
  19. Yang, D.; Guo, H.; Chen, X.; Wang, L.; Jiang, P.; Zhang, W.; Zhang, L.; Wang, Z.L. A flexible and wide pressure range triboelectric sensor array for real-time pressure detection and distribution mapping. J. Mater. Chem. A 2020, 8, 23827–23833.
  20. Novoselov, K.S.; Geim, A.K.; Morozov, S.V.; Jiang, D.; Zhang, Y.; Dubonos, S.V.; Grigorieva, I.V.; Firsov, A.A. Electric field effect in atomically thin carbon films. Science 2004, 306, 666–669.
  21. Sheng, L.; Liao, T.; Kou, L.; Sun, Z. Single-crystalline ultrathin 2D TiO2 nanosheets: A bridge towards superior photovoltaic devices. Mater. Today Energy 2017, 3, 32–39.
  22. Zong, B.; Xu, Q.; Li, Q.; Fang, X.; Chen, X.; Liu, C.; Zang, J.; Bo, Z.; Mao, S. Novel insights into the unique intrinsic sensing behaviors of 2D nanomaterials for volatile organic compounds: From graphene to MoS2 and black phosphorous. J. Mater. Chem. A 2021, 9, 14411–14421.
  23. Liu, D.; Zhang, S.; Wang, J.; Peng, T.; Li, R. Direct Z-Scheme 2D/2D photocatalyst based on ultrathin g-C3N4 and WO3 nanosheets for efficient visible-light-driven H2 generation. ACS Appl. Mater. Interfaces 2019, 11, 27913–27923.
  24. Feng, R.; Lei, W.; Sui, X.; Liu, X.; Qi, X.; Tang, K.; Liu, G.; Liu, M. Anchoring black phosphorus quantum dots on molybdenum disulfide nanosheets: A 0D/2D nanohybrid with enhanced visible−and NIR−light photoactivity. Appl. Catal. B Environ. 2018, 238, 444–453.
  25. Zong, L.; Li, X.; Zhu, L.; You, J.; Li, Z.; Gao, H.; Li, M.; Li, C. Photo-responsive heterojunction nanosheets of reduced graphene oxide for photo-detective flexible energy devices. J. Mater. Chem. A 2019, 7, 7736–7744.
  26. Guiney, L.M.; Mansukhani, N.D.; Jakus, A.E.; Wallace, S.G.; Shah, R.N.; Hersam, M.C. Three-dimensional printing of cytocompatible, thermally conductive hexagonal boron nitride nanocomposites. Nano Lett. 2018, 18, 3488–3493.
  27. Hamzah, A.A.; Selvarajan, R.S.; Majlis, B.Y. Graphene for biomedical applications: A review. Sains Malays. 2017, 46, 1125–1139.
  28. Chen, J.; Ding, P.; Pan, R.; Xuan, W.; Guo, D.; Ye, Z.; Yin, W.; Jin, H.; Wang, X.; Dong, S.; et al. Self-powered transparent glass-based single electrode triboelectric motion tracking sensor array. Nano Energy 2017, 34, 442–448.
  29. Li, Q.; Zhang, L.N.; Tao, X.M.; Ding, X. Review of flexible temperature sensing networks for wearable physiological monitoring. Adv. Healthc. Mater. 2017, 6, 1601371.
  30. Huynh, T.-P.; Haick, H. Autonomous flexible sensors for health monitoring. Adv. Mater. 2018, 30, 1802337.
  31. Ribas Ripoll, V.; Vellido, A. Blood pressure assessment with differential pulse transit time and deep learning: A proof of concept. Kidney Dis. 2019, 5, 23–27.
  32. Le, T.; Ellington, F.; Lee, T.-Y.; Vo, K.; Khine, M.; Krishnan, S.K.; Dutt, N.; Cao, H. Continuous non-invasive blood pressure monitoring: A methodological review on measurement techniques. IEEE Access 2020, 8, 212478–212498.
  33. Quan, X.; Liu, J.; Roxlo, T.; Siddharth, S.; Leong, W.; Muir, A.; Cheong, S.-M.; Rao, A. Advances in non-invasive blood pressure monitoring. Sensors 2021, 21, 4273.
  34. Stewart, J.; Stewart, P.; Walker, T.; Horner, D.V.; Lucas, B.; White, K.; Muggleton, A.; Morris, M.; Selby, N.M.; Taal, M.W. A Feasibility study of non-invasive continuous estimation of brachial pressure derived from arterial and venous lines during dialysis. IEEE J. Transl. Eng. Health Med. 2020, 9, 2700209.
  35. Shoji, T.; Nakagomi, A.; Okada, S.; Ohno, Y.; Kobayashi, Y. Invasive validation of a novel brachial cuff-based oscillometric device (SphygmoCorXCEL) for measuring central blood pressure. J. Hypertens. 2017, 35, 69–75.
  36. He, H.; Pang, Y.; Cui, K. Study on signal processing and uniform deflation of wrist electronic sphygmomanometer. Int. Core J. Eng. 2022, 8, 782–792.
  37. Mirdamadi, A.; Etebari, M. Comparison of manual versus automated blood pressure measurement in intensive care unit, coronary care unit, and emergency room. ARYA Atheroscler. 2017, 13, 29–34.
  38. Dal Pont, M.P.; Marques, J.L.B. Reflective photoplethysmography acquisition platform with monitoring modules and noninvasive blood pressure calculation. IEEE Trans. Instrum. Meas. 2020, 69, 5649–5657.
  39. Ray, D.; Collins, T.; Woolley, S.; Ponnapalli, P. A review of wearable multi-wavelength photoplethysmography. IEEE Rev. Biomed. Eng. 2021, 16, 136–151.
  40. Chandrasekhar, A.; Yavarimanesh, M.; Natarajan, K.; Hahn, J.-O.; Mukkamala, R. PPG sensor contact pressure should be taken into account for cuff-less blood pressure measurement. IEEE Trans. Biomed. Eng. 2020, 67, 3134–3140.
  41. Stapleton, A.; Ivanov, M.S.; Noor, M.R.; Silien, C.; Gandhi, A.A.; Soulimane, T.; Kholkin, A.L.; Tofail, S.A.M. Converse piezoelectricity and ferroelectricity in crystals of lysozyme protein revealed by piezoresponse force microscopy. Ferroelectrics 2018, 525, 135–145.
  42. De Souza Marinho, D.; Pinto, F.R.; Baptista, E.R. Piezoelectric effect as an energy generator: A describal historic of its performance. Int. J. Adv. Eng. Res. Sci. 2019, 6, 228–232.
  43. Ico, G.; Myung, A.; Kim, B.S.; Myung, N.V.; Nam, J. Transformative piezoelectric enhancement of P(VDF-TrFE) synergistically driven by nanoscale dimensional reduction and thermal treatment. Nanoscale 2018, 10, 2894–2901.
  44. Yang, T.; Xie, D.; Li, Z.; Zhu, H. Recent advances in wearable tactile sensors: Materials, sensing mechanisms, and device performance. Mater. Sci. Eng. R Rep. 2022, 115, 1–37.
  45. Osoinach, B. Proximity Capacitive Sensor Technology for Touch Sensing Applications. Available online: Cache.freescale.com/files/sensors/doc/white_paper/PROXIMITYWP.pdf (accessed on 5 November 2022).
  46. Berggren, C.; Bjarnason, B.; Johansson, G. Capacitive biosensors. Electroanalysis 2001, 13, 173–180.
  47. Lin, L.; Chung, C.-K. PDMS Microfabrication and design for microfluidics and sustainable energy application: Review. Micromachines 2021, 12, 1350.
  48. Tang, C.; Liu, Z.; Li, L. Mechanical sensors for cardiovascular monitoring: From battery-powered to self-powered. Biosensors 2022, 12, 651.
  49. Verma, P.; Punetha, D.; Pandey, S.K. Sensitivity optimization of MEMS based piezoresistive pressure sensor for harsh environment. Silicon 2020, 12, 2663–2671.
  50. Bao, M. Analysis and Design Principles of MEMS Devices; Elsevier Science: Amsterdam, The Netherlands, 2005.
  51. Duan, L.; D’hooge, D.; Cardon, L. Recent progress on flexible and stretchable piezoresistive strain sensors: From design to application. Prog. Mater. Sci. 2020, 114, 100617.
  52. Wang, Z.L. From contact electrification to triboelectric nanogenerators. Rep. Prog. Phys. 2021, 84, 096502.
  53. Tao, J.; Bao, R.; Wang, X.; Peng, Y.; Li, J.; Fu, S.; Pan, C.; Wang, Z.L. Self-powered tactile sensor array systems based on the triboelectric effect. Adv. Funct. Mater. 2018, 29, 1806379.
  54. Askari, H.; Khajepour, A.; Khamesee, M.B.; Saadatnia, Z.; Wang, Z.L. Piezoelectric and triboelectric nanogenerators: Trends and impacts. Nano Today 2018, 22, 10–13.
  55. Qiu, A.; Li, P.; Yang, Z.; Yao, Y.; Lee, I.; Ma, J. A path beyond metal and silicon:Polymer/nanomaterial composites for stretchable strain sensors. Adv. Func. Mat. 2019, 29, 1806306.
  56. Zhang, Y.; Yang, J.; Hou, X.; Li, G.; Wang, L.; Bai, N.; Cai, M.; Zhao, L.; Wang, Y.; Zhang, J.; et al. Highly stable flexible pressure sensors with a quasi-homogeneous composition and interlinked interfaces. Nat. Commun. 2022, 13, 1317.
  57. Li, C.; Huang, K.; Yuan, T.; Cong, T.; Fan, Z.; Pan, L. Fabrication and conductive mechanism analysis of stretchable electrodes based on PDMS-Ag nanosheet composite with low resistance, stability, and durability. Nanomaterials 2022, 12, 2628.
  58. Pan, S.; Liu, Z.; Wang, M.; Jiang, Y.; Luo, Y.; Wan, C.; Qi, D.; Wang, C.; Ge, X.; Chen, X. Mechanocombinatorially screening sensitivity of stretchable strain sensors. Adv. Mater. 2019, 31, 1903130.
  59. Chakraborty, B.; Ray, P.; Garg, N.; Banerjee, S. High capacity reversible hydrogen storage in titanium doped 2D carbon allotrope Ψ-graphene: Density Functional Theory investigations. Int. J. Hydrog. Energy 2021, 46, 4154–4167.
  60. Kumar, R.; Youssry, S.M.; Soe, H.M.; Abdel-Galeil, M.M.; Kawamura, G.; Matsuda, A. Honeycomb-like open-edged reduced-graphene-oxide-enclosed transition metal oxides (NiO/Co3O4) as improved electrode materials for high-performance supercapacitor. J. Energy Storage 2020, 30, 101539.
  61. Zulkepli, N.; Yunas, J.; Mohamed, M.A.; Sirat, M.S.; Hamzah, A.A. Atmospheric pressure chemical vapour deposition growth of graphene for the synthesis of SiO2 based graphene ball. Sains Malays. 2022, 51, 1927–1932.
  62. Zhang, H. Ultrathin two-dimensional nanomaterials. ACS Nano 2015, 9, 9451–9469.
  63. Olabi, A.G.; Wilberforce, T.; Sayed, E.T.; Elsaid, K.; Rezk, H.; Abdelkareem, M.A. Recent progress of graphene based nanomaterials in bioelectrochemical systems. Sci. Total Environ. 2020, 749, 141225.
  64. Cui, H.; Guo, Y.; Ma, W.; Zhou, Z. 2 D materials for electrochemical energy storage: Design, preparation, and application. ChemSusChem 2020, 13, 1155–1171.
  65. Shazni, M.A.; Lee, M.W.; Lee, H.W. Highly-sensitive graphene-based flexible pressure sensor platform. Sains Malays. 2017, 46, 1155–1161.
  66. Zhang, H.; Ren, S.; Pu, J.; Xue, Q. Barrier mechanism of multilayers graphene coated copper against atomic oxygen irradiation. Appl. Surf. Sci. 2018, 444, 28–35.
  67. Govindasamy, M.; Jian, C.-R.; Kuo, C.-F.; Hsieh, A.-H.; Sie, J.-L.; Huang, C.-H. A chemiresistive biosensor for detection of cancer biomarker in biological fluids using CVD-grown bilayer graphene. Microchim. Acta 2022, 189, 374.
  68. Shen, C.; Li, X.; Li, N.; Xie, K.; Wang, J.-G.; Liu, X.; Wei, B. Graphene-boosted, high-performance aqueous Zn-ion battery. ACS Appl. Mater. Interfaces 2018, 10, 25446–25453.
  69. Li, G.; Law, W.-C.; Chan, K.C. Floating, highly efficient, and scalable graphene membranes for seawater desalination using solar energy. Green Chem. 2018, 20, 3689–3695.
  70. Burdanova, M.G.; Kharlamova, M.V.; Kramberger, C.; Nikitin, M.P. Applications of Pristine and Functionalized Carbon Nanotubes, Graphene, and Graphene Nanoribbons in Biomedicine. Nanomaterials 2021, 11, 3020.
  71. Wang, Q.H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J.N.; Strano, M.S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nat. Nanotech. 2012, 7, 699–712.
  72. Park, J.; Hwang, J.C.; Kim, G.G.; Park, J.-U. Flexible electronics based on one-dimensional and two-dimensional hybrid nanomaterials. InfoMat 2019, 2, 33–56.
  73. Naghdi, S.; Rhee, K.Y.; Hui, D.; Park, S.J. A Review of Conductive Metal Nanomaterials as Conductive, Transparent, and Flexible Coatings, Thin Films, and Conductive Fillers: Different Deposition Methods and Applications. Coatings 2018, 8, 278.
  74. Kamyshny, A.; Magdassi, S. Conductive Nanomaterials for Printed Electronics. Small 2014, 10, 3515–3535.
  75. Xie, J.; Chen, Q.; Shen, H.; Li, G. Wearable graphene devices for sensing. J. Electrochem. Soc. 2020, 167, 037541.
  76. Prakash, J.; Prema, D.; Venkataprasanna, K.S.; Balagangadharan, K.; Selvamurugan, N.; Venkatasubbu, G.D. Nanocomposite chitosan film containing graphene oxide/hydroxyapatite/gold for bone tissue engineering. Int. J. Biol. Macromol. 2020, 154, 62–71.
  77. Derakhshi, M.; Daemi, S.; Shahini, P.; Habibzadeh, A.; Mostafavi, E.; Ashkarran, A.A. Two-dimensional nanomaterials beyond graphene for biomedical applications. J. Funct. Biomater. 2022, 13, 27.
  78. Chand, R.; Ramalingam, S.; Neethirajan, S. A 2D transition-metal dichalcogenide MoS2 based novel nanocomposite and nanocarrier for multiplex miRNA detection. Nanoscale 2018, 10, 8217–8225.
  79. Andrzejewski, D.; Myja, H.; Heuken, M.; Grundmann, A.; Kalisch, H.; Vescan, A.; Kümmell, T.; Bacher, G. Scalable large-area p–i–n light-emitting diodes based on WS2 monolayers grown via MOCVD. ACS Photonics 2019, 6, 1832–1839.
  80. Zhang, F.; Zhang, H.; Krylyuk, S.; Milligan, C.A.; Zhu, Y.; Zemlyanov, D.Y.; Bendersky, L.A.; Burton, B.P.; Davydov, A.V.; Appenzeller, J. Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories. Nat. Mater. 2018, 18, 55–61.
  81. Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M.W. Two-dimensional nanocrystals produced by exfoliation of Ti3AlC2. Adv. Mater. 2011, 23, 4248–4253.
  82. Zulkepli, N.; Yunas, J.; Mohamed, M.A.; Sirat, M.S.; Hamzah, A.A. Atmospheric pressure chemical vapour deposition growth of graphene for the synthesis of SiO2 based graphene ball. Sains Malays. 2022, 51, 1927–1932.
  83. Zhang, H. Ultrathin two-dimensional nanomaterials. ACS Nano 2015, 9, 9451–9469.
  84. Olabi, A.G.; Wilberforce, T.; Sayed, E.T.; Elsaid, K.; Rezk, H.; Abdelkareem, M.A. Recent progress of graphene based nanomaterials in bioelectrochemical systems. Sci. Total Environ. 2020, 749, 141225.
  85. Cui, H.; Guo, Y.; Ma, W.; Zhou, Z. 2 D materials for electrochemical energy storage: Design, preparation, and application. ChemSusChem 2020, 13, 1155–1171.
  86. Shazni, M.A.; Lee, M.W.; Lee, H.W. Highly-sensitive graphene-based flexible pressure sensor platform. Sains Malays. 2017, 46, 1155–1161.
  87. Zhang, H.; Ren, S.; Pu, J.; Xue, Q. Barrier mechanism of multilayers graphene coated copper against atomic oxygen irradiation. Appl. Surf. Sci. 2018, 444, 28–35.
  88. Okubo, M.; Sugahara, A.; Kajiyama, S.; Yamada, A. MXene as a charge storage host. Acc. Chem. Res. 2018, 51, 591–599.
  89. Deysher, G.; Shuck, C.E.; Hantanasirisakul, K.; Frey, N.C.; Foucher, A.C.; Maleski, K.; Sarycheva, A.; Shenoy, V.B.; Stach, V.B.; Anasori, V.B.; et al. Synthesis of Mo4VAlC4 MAX phase and two-dimensional Mo4VC4 MXene with five atomic layers of transition metals. ACS Nano 2020, 14, 204–217.
  90. Lv, G.; Wang, J.; Shia, Z.; Fan, L. Intercalation and delamination of two-dimensional MXene (Ti3C2Tx) and application in sodium-ion batteries. Mater. Lett. 2018, 219, 45–50.
  91. Ma, W.; Yang, K.; Wang, H.; Li, H. Poly(vinylidene fluoride-co-hexafluoropropylene)-MXene nanosheet composites for microcapacitors. Appl. Nano Mater. 2020, 3, 7992–8003.
  92. Ayman, I.; Rasheed, A.; Ajmal, S.; Rehman, A.; Ali, A.; Shakir, I.; Warsi, M.F. CoFe2O4 nanoparticle-decorated 2D MXene: A novel hybrid material for supercapacitor applications. Energy Fuels 2020, 34, 7622–7630.
  93. Wang, J.; Cai, Z.; Lin, D.; Chen, K.; Zhao, L.; Xie, F.; Su, R.; Xie, W.; Liu, P.; Zhu, R. Plasma oxidized Ti3C2Tx MXene as electron transport layer for efficient perovskite solar cells. Appl. Mater. Interfaces 2021, 13, 32495–32502.
  94. Ma, C.; Ma, M.; Si, C.; Ji, X.; Wan, P. Flexible MXene-based composites for wearable devices. Adv. Func. Mat. 2021, 31, 2009524.
  95. Parajuli, D.; Murali, N.; Devendra, K.C.; Karki, B.; Samatha, K.; Kim, A.A.; Park, M.; Pant, B. Advancements in MXene-polymer nanocomposites in energy storage and biomedical applications. Polymers 2022, 14, 3433.
  96. Wang, X.; Bannenberg, L. Design and characterization of 2D MXene-based electrode with high-rate capability. MRS Bull. 2021, 46, 755–766.
  97. Ovbiagele, B.; Diener, H.; Yusuf, S.; Martin, R.H.; Cotton, D.; Vinisko, R.; Donnan, G.A.; Bath, P.M.; PRoFESS Investigators. Level of systolic blood pressure within the normal range and risk of recurrent stroke. JAMA 2011, 306, 2137–2144.
  98. Wang, Q.H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J.N.; Strano, M.S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nat. Nanotech. 2012, 7, 699–712.
  99. Derakhshi, M.; Daemi, S.; Shahini, P.; Habibzadeh, A.; Mostafavi, E.; Ashkarran, A.A. Two-dimensional nanomaterials beyond graphene for biomedical applications. J. Funct. Biomater. 2022, 13, 27.
  100. Chand, R.; Ramalingam, S.; Neethirajan, S. A 2D transition-metal dichalcogenide MoS2 based novel nanocomposite and nanocarrier for multiplex miRNA detection. Nanoscale 2018, 10, 8217–8225.
  101. Andrzejewski, D.; Myja, H.; Heuken, M.; Grundmann, A.; Kalisch, H.; Vescan, A.; Kümmell, T.; Bacher, G. Scalable large-area p–i–n light-emitting diodes based on WS2 monolayers grown via MOCVD. ACS Photonics 2019, 6, 1832–1839.
  102. Zhang, F.; Zhang, H.; Krylyuk, S.; Milligan, C.A.; Zhu, Y.; Zemlyanov, D.Y.; Bendersky, L.A.; Burton, B.P.; Davydov, A.V.; Appenzeller, J. Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories. Nat. Mater. 2018, 18, 55–61.
  103. Qiu, D.; Chu, Y.; Zeng, H.; Xu, H.; Dan, G. Stretchable MoS2 electromechanical sensors with ultrahigh sensitivity and large detection range for skin-on monitoring. ACS Appl. Mater. Interfaces 2019, 11, 37035–37042.
  104. Mohamed, A.; Marciniak, M.; Williamson, W.; Huckstep, O.J.; Lapidaire, W.; Mccance, A.; Neubauer, S.; Leeson, P.; Lewandowski, A.J. Association of systolic blood pressure elevation with disproportionate left ventricular remodeling in very preterm-born young adults: The preterm heart and elevated blood pressure. JAMA Cardiol. 2021, 6, 821–829.
  105. Ismail, S.N.A.; Nayan, N.A.; Jaafar, R.; May, Z. Recent Advances in Non-Invasive Blood Pressure Monitoring and Prediction Using a Machine Learning Approach. Sensors 2022, 22, 6195.
  106. Yang, G.; Pang, G.; Pang, Z.; Gu, Y.; Mäntysalo, M.; Yang, H. Non-invasive flexible and stretchable wearable sensors with nano-based enhancement for chronic disease care. IEEE Rev. Biomed. Eng. 2019, 12, 34–71.
  107. Noh, S.; Yoon, C.; Hyun, E.; Yoon, H.N.; Chung, T.J.; Park, K.S.; Kim, H.C. Ferroelectret film-based patch-type sensor for continuous blood pressure monitoring. Electron. Lett. 2014, 50, 143–144.
  108. Okubo, M.; Sugahara, A.; Kajiyama, S.; Yamada, A. MXene as a charge storage host. Acc. Chem. Res. 2018, 51, 591–599.
  109. Deysher, G.; Shuck, C.E.; Hantanasirisakul, K.; Frey, N.C.; Foucher, A.C.; Maleski, K.; Sarycheva, A.; Shenoy, V.B.; Stach, V.B.; Anasori, V.B.; et al. Synthesis of Mo4VAlC4 MAX phase and two-dimensional Mo4VC4 MXene with five atomic layers of transition metals. ACS Nano 2020, 14, 204–217.
  110. Lv, G.; Wang, J.; Shia, Z.; Fan, L. Intercalation and delamination of two-dimensional MXene (Ti3C2Tx) and application in sodium-ion batteries. Mater. Lett. 2018, 219, 45–50.
  111. Ma, W.; Yang, K.; Wang, H.; Li, H. Poly(vinylidene fluoride-co-hexafluoropropylene)-MXene nanosheet composites for microcapacitors. Appl. Nano Mater. 2020, 3, 7992–8003.
  112. Laurila, M.M.; Peltokangas, M.; Montero, K.L.; Verho, J.; Haapala, M.; Oksala, N.; Vehkaoja, A.; Mäntysalo, M. Self-powered, high sensitivity printed e-tattoo sensor for unobtrusive arterial pulse wave monitoring. Nano Energy 2022, 102, 107625.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
This entry is offline, you can click here to edit this entry!
Video Production Service
Feedback