GO/CNT-OH/Nafion Nanocomposite Humidity Sensor Based on the LC Wireless Method.

In recent years, LC resonant sensors have gained widespread attention for their extensive applications in industries such as pharmaceutical storage and food transportation. A wireless passive sensor with a good sensing performance is proposed based on a GO/CNT-OH/Nafion nanocomposite. The sensor was fabricated via inkjet printing technology, and the surface morphology of the GO/CNT-OH/Nafion nanocomposite was characterized by SEM measurement. It is found that the MWCNTs support the GO layer and the hydrophobic chains of Nafion interact with the hydrophobic layer of GO, resulting in a larger cavity and hydrophilic surface of the entire material. This structure well reflects the fact that the mixing of MWCNTs and Nafion provides the entire material with a stronger water absorption. The experimental study shows that the proposed humidity sensor has a frequency variation of 103 kHz/%RH at low humidity (30-60% RH) and a sensitivity of 931 kHz/%RH at high humidity (60-95% RH), while the sensitivity value from 30-95% RH is 547 kHz/% RH. The response time and recovery time are 110 s and 115 s, respectively. In addition, the tests showed that the GO/CNT-OH/Nafion nanocomposite applied to the humidity sensor had a maximum humidity hysteresis of about 3% RH at 30-95% RH, the resonant frequency remained basically unchanged after 50 h of testing, and the whole sensor possessed a good stability. After conducting several repeated experiments, it was found that the resonant frequency error of the whole sensor was low and did not affect the overall sensing test, which proved the reproducible preparation of the sensor. Finally, the humidity-sensing mechanism of the proposed sensor was analyzed in this paper, and it was found that GO enhanced the hygroscopic properties of GO/CNT-OH/Nafion nanocomposite when it was supported by MWCNT-OH and included uniformly dispersed Nafion. Therefore, our proposed humidity sensor is suitable for humidity detection above 30% RH in both sealed and open environments.

Finite Element Analysis Model of Electronic Skin Based on Surface Acoustic Wave Sensor.

In recent years, with the rapid development of flexible electronic devices, researchers have a great interest in the research of electronic skin (e-skin). Traditional e-skin, which is made of rigid integrated circuit chips, not only limits the overall flexibility, but also consumes a lot of power and poses certain security risks to the human body. In this paper, a wireless passive e-skin is designed based on the surface acoustic wave sensor (SAWS) of lithium niobate piezoelectric film. The e-skin has the advantages of small size, high precision, low power consumption, and good flexibility. With the multi-sensing function of stress, temperature, and sweat ion concentration, etc., the newly designed e-skin is a sensor platform for a wide range of external stimuli, and the measurement results can be directly presented in frequency. In order to explore the characteristic parameters and various application scenarios of the SAWS, finite element analysis is carried out using the simulation software; the relationship between the SAWS and various influencing factors is explored, and the related performance curve is obtained. These simulation results provide important reference and experimental guidance for the design and preparation of SAW e-skin.

Wearable biosensors for real-time sweat analysis and body motion capture based on stretchable fiber-based triboelectric nanogenerators.

Carbon neutrality is a global green energy revolution meaning that the carbon dioxide can make ends meet. However, with the mushroom of the fifth generation wireless systems (5G) and the Internet of Things (IoT), it is a great challenge for powering the ubiquitous distributed devices, because the battery production and high overhead maintenance may bring more carbon emissions. Here, we present wearable biosensors for real-time sweat analysis and body motion capture based on stretchable fiber-based triboelectric nanogenerators (F-TENG). The F-TENG is made of stretchable conductive fiber (Ecoflex coating with polyaniline (PANI)) and varnished wires. Based on the coupling effect of triboelectric effect and enzymatic reaction (surface-triboelectric coupling effect), the wearable biosensors can not only precisely sense the motion states, but also detect glucose, creatinine and lactate acid in sweat in real-time. Importantly, the wearable devices can self-drive without any external power source and the response against glucose, creatinine and lactate acid can be up to 103%, 125% and 38%, respectively. On this basis, applications in biosensing and wireless communication have been demonstrated. This work exhibits a prospective potential application of F-TENG in IoT for diverse use.

Assigning viscoelastic and hyperelastic properties to the middle-ear soft tissues for sound transmission.

A finite element model of the human ear considering viscoelasticity and hyperelasticity of the middle-ear (ME) soft tissues is developed in this paper. The present model is validated by comparing the static and dynamic responses to experimental data. The model-derived results are in good agreement with existing measurements. On this basis, the dynamic response of the ME under static pressure is re-evaluated. The results show that the static pressure mainly affects the low-frequency responses of the ME below 1000 Hz. In the case of static pressure preloading, the low-frequency displacement of the tympanic membrane and the stapes footplate (SF) and the ME gain are decreased, while the reverse ME impedance is increased. This is because the effective stiffness of the ME is increased due to large deformation and material nonlinearity, resulting in a decrease in the forward response of the ME at frequencies below 1000 Hz. Furthermore, the contribution of viscoelasticity to the ME sound transmission is also discussed. With the consideration of viscoelasticity, the magnitude of the SF displacement increases at frequencies above 3000 Hz, and the phase is mainly increased in the frequency band of 2000-5000 Hz. Moreover, viscoelasticity is more important for the SF displacement under static pressure. Given that only one type of material property (hyperelasticity or viscoelasticity) is considered in most published models, the consideration of both viscoelasticity and hyperelasticity helps to establish an accurate human ear model.

Rs5498 polymorphism may be a risk factor for coronary heart disease in Chinese population: evidence from a meta-analysis involving 5537 subjects.

Despite large numbers of studies from Chinese population related to the association between rs5498 polymorphism and coronary heart disease (CHD) risk, the results are inconsistent probably due to the difference in the nationalities. To further evaluate the impact of the rs5498 polymorphism on CHD risk of different nationalities population, we performed this meta-analysis. We comprehensively searched the eligible studies for the present meta-analysis through China National Knowledge Infrastructure (CNKI), PubMed, EMBASE databases. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were obtained to evaluate the strength of the association between rs5498 polymorphism and CHD risk. Finally, a total of 18 studies including 5537 subjects met the inclusion criteria. The pooled result showed that the rs5498 polymorphism was significantly associated with an increased risk of CHD in allele comparison model (OR=1.43, 95% CI=1.17-1.73, P=0.000), homozygote model (OR=1.23, 95% CI=1.03-1.46, P=0.000), heterozygote model (OR=1.23, 95% CI=1.03-1.46, P=0.018), dominant model (OR=1.45, 95% CI=1.21-1.74, P=0.001) and recessive model (OR=2.17, 95% CI=1.70-2.77, P=0.002). But subgroup analysis only supported the results from data of Han and Zhuang population in South China and North China. We did not find any evidences revealing some relationship between them in the Uygur population of Northwest China. Totally, the results of our meta-analysis indicate that the rs5498 polymorphism may be associated with coronary heart disease in Han and Zhuang population but not in Uyghur population. A large number of well-designed and multiracial studies should be conducted to re-evaluate the relationship.