Graphene oxide/polydimethylsiloxane composite sponge for removing Pb(ii) from water

An efficient adsorbent to remove Pb(ii) from water was prepared by treating polydimethylsiloxane (PDMS) sponge with polyvinyl alcohol and then coating the sponge with graphene oxide (GO). The GO–PDMS sponge was highly hydrophilic, easily handled during and after use, and easily recycled. The kinetics and isotherms of Pb(ii) sorption onto the GO–PDMS sponge were investigated by performing batch sorption tests. The kinetics of Pb(ii) sorption onto the GO–PDMS sponge indicated that sorption equilibrium occurred rapidly (within 60 min) and that the sorption data could be described using a pseudo-second-order model. Maximum Pb(ii) sorption onto the GO–PDMS sponge occurred at pH > 5. Increasing GO loading on the PDMS sponge increased the amount of Pb(ii) that could be sorbed. The isotherm for Pb(ii) sorption onto the GO–PDMS sponge was non-linear and was well described by the Langmuir isotherm model, indicating that Pb(ii) sorption onto the GO–PDMS sponge was homogeneous and occurred through sorption of a monolayer of Pb(ii). The GO–PDMS sponge, used as a filter, removed Pb(ii) efficiently from water. The Pb(ii) removal efficiencies were more than 50% and the maximum was 85%.

A novel sorbent material for Pb(ii) sorption was created by coating graphene oxide (GO) on a pretreated PDMS sponge.     

A flexible and highly sensitive pressure sensor based on three-dimensional electrospun carbon nanofibers

High-performance flexible pressure sensors with high sensitivity are important components of the systems for healthcare monitoring, human–machine interaction, and electronic skin. Herein, a flexible and highly sensitive pressure sensor composed of ferrosoferric oxide (Fe₃O₄)/carbon nanofibers (FeOCN) was fabricated using three-dimensional electrospinning and further heat treatment methods. The obtained pressure sensor demonstrates a wide working range (0–4.9 kPa) and a high sensitivity of 0.545 kPa⁻¹ as well as an ultralow detection limit of 6 Pa. Additionally, the pressure sensor exhibits a rapid response time, good stability, high hydrophobicity, and excellent flexibility. These merits endow the pressure sensor with the ability to precisely detect wrist pulse, phonation, breathing, and finger bending in real-time. Therefore, the FeOCN pressure sensor presents a promising application in real-time healthcare monitoring.

A three-dimensional electrospun carbon nanofiber network was used to measure press strains with high sensitivity.     

基于微机电系统运动传感器在人体运动测量中的应用

背景：基于微机电系统的运动传感器以其安装简易、使用便利、成本低廉的特点给人体运动测量变革带来了契机。目的：分析总结运动传感器中适合人体运动测量的几型传感器,以及利用这些运动传感器取得的研究成果。方法：应用计算机检索CNKI和ISI数据库中2005/2011-08关于基于微机电系统运动传感器技术的文章,在标题和摘要中以＂微机电系统、运动传感器、人体运动＂或＂micro electro mechanical systems sensor,human motion,human movement＂为检索词进行检索。选择内容与微机电系统运动传感器技术在人体运动测量中的应用相关的文章,且尽量选择近5年发表或发表在权威杂志的文章。结果与结论：初检得到180篇文献,根据纳入标准选择34篇文章进行综述。人体运动测量中对各种运动传感器技术的关注和应用越来越多,运动传感器能够迅速简便地检测人体的运动信息,而其捕获的运动信息可广泛运用于各种临床领域。随着软硬件技术的不断发展将成为人体运动测量的主流手段。     

Flexible and high-performance piezoresistive strain sensors based on multi-walled carbon nanotubes@polyurethane foam

Flexible wearable pressure sensors have attracted special attention in the last 10 years due to their great potential in health monitoring, activity detection and as electronic skin. However, it is still a great challenge to develop high sensitivity, fast response, and good reliable stability through a simple and reproducible large-scale fabrication process. Here, we develop a simple and efficient method to fabricate three-dimensional (3D) light-weight piezoresistive sensing materials by coating multi-walled carbon nanotubes (MWCNTs) on the surface of polyurethane (PU) foam using a dip-spin coating process. The PU foam prepared with SEBS-g-MAH and polyether polyols has high elasticity and good stability in MWCNTs/DMF solution. Subsequently, a piezoresistive sensor was assembled with the prepared MWCNTs/PU composite foam and copper foil electrodes. The assembled pressure sensor has high sensitivity (62.37 kPa⁻¹), a wide working range (0–172.6 kPa, 80% strain), a fast response time (less than 0.6 s), and reliable repeatability (≥2000 cycles). It has shown potential application in real-time human motion detection (e.g., arm bending, knee bending), and monitoring the brightness of LED lights.

A 3D light-weight piezoresistive sensor with high sensitivity, wide working range, fast response time, and reliable repeatability was developed and can be applied to real-time human motion detection and monitoring the brightness of LED lights.     

A highly accurate flexible sensor system for human blood pressure and heart rate monitoring based on graphene/sponge

The development of wearable devices has shown tremendous dynamism, which places greater demands on the accuracy and consistency of sensors. This work reports a flexible sensing system for human health monitoring of parameters such as human pulse waveform, blood pressure and heart rate. The signal acquisition part is a vertically structured piezoresistive micro-pressure flexible sensor. To ensure accuracy, the sensors are filled with melamine sponge covered by graphene nanoconductive materials as the conductive layer, and ecoflex material acts as the flexible substrate. The flexible sensors fabricated under the 3D printing mold-assisted method exhibited high accuracy, good repeatability and remarkable response to micro-pressure. However, when used for human pulse signal measurement, the sensors are affected by unavoidable interference. In order to collect human health data accurately, signal acquisition and processing systems were constructed. The system allows for the accurate acquisition of human pulse signals, accompanied by the function of non-invasive, real-time and continuous detection of human blood pressure heart rate parameters. By comparing with an Omron blood pressure monitor, the blood pressure heart rate index error of the flexible sensing system does not exceed 3%.

We fabricated a flexible sensing system, including the preparation of sensors and construction of the signal processing computing platform, which enabled human health monitoring by collecting pulse signals.     

聚氨酯/多壁碳纳米管复合材料电纺丝支架对成纤维细胞生长的促进

应用电纺丝方法制备纤维直径为300～500nm的多壁碳纳米管/聚氨酯复合材料,以无纺膜材料作为细胞支架,选择在促进组织修复和再生中起重要作用的成纤维细胞株作为实验细胞。通过扫描电镜对多壁碳纳米管/聚氨酯无纺膜及聚氨酯无纺膜的微观形貌进行表征;通过细胞黏附实验、增殖实验以及细胞骨架发育观察,探讨无纺膜的微观纳米拓扑结构及多壁碳纳米管的复合对细胞的作用;并进一步采用双层细胞培养装置,分析多壁碳纳米管/聚氨酯无纺膜通过细胞通讯途径对在其他材料上生长的细胞生长行为的影响。实验结果表明,无纺膜中的纳米纤维网络结构和多壁碳纳米管成分不仅能够显著促进细胞的黏附和增殖,而且有利于细胞的迁移和聚集;另外,生长在多壁碳纳米管/聚氨酯无纺膜支架上的细胞可能通过旁分泌方式将某些生物大分子分泌到细胞外液中,经局部扩散作用于在其他材料上生长的细胞,促进其增殖。因此,多壁碳纳米管/聚氨酯纳米纤维无纺膜为细胞提供了接近天然细胞外基质的人造微环境,显示了该支架在引导组织修复和再生中的应用潜力。     

Humidity sensor based on poly(lactic acid)/PANI–ZnO composite electrospun fibers

The electrospinning technique has been successfully used to prepared micro-fibers of the poly(lactic acid)/polyaniline–zinc oxide (PLA/PANI–ZnO) composite. The polyaniline–zinc oxide (PANI–ZnO) nanocomposites are synthesized by hydrothermal and in situ polymerization methods. X-ray diffraction techniques are used to study the structural properties of the PLA/PANI–ZnO composite fibers and the PANI–ZnO nanocomposite. The average crystallite size of the PANI–ZnO nanocomposite is found to be 36 nm. The morphology and diameter of the composite fibers are analyzed by scanning electron microscopy (SEM). The average fiber diameter of the pure poly(lactic acid) (PLA) fiber is around 2.5 μm and that of the PLA/PANI–ZnO composite fiber is around 1.4 μm. Differential scanning calorimetry (DSC) provides the thermal properties of the PLA/PANI–ZnO composite fibers. The melting temperature (T_m) for the pure PLA is observed at 149.3 °C, and it is shifted to 153.0 °C for the PLA/PANI–ZnO composite fibers. The enhanced thermal properties of the composite fibers are due to the interaction between the polymer and the nanoparticles. The water contact angle measurements probe the surface hydrophilicity of the PLA/PANI–ZnO composite fibers. The role of the PANI–ZnO nanocomposite on the sensing behavior of PLA fibers has also been investigated. The humidity sensing properties of the composite fiber based sensor are studied in the relative humidity (RH) range of 20–90% RH. The experimental results show that the composite fiber exhibited good response (85 s) and recovery (120 s) times. These results indicate that the one-dimensional (1D) fiber structure enhances the humidity sensing properties.

The electrospinning technique has been successfully used to prepared micro-fibers of the poly(lactic acid)/polyaniline–zinc oxide (PLA/PANI–ZnO) composite for humidity sensor application.     

Physiological motion monitoring: a wearable device and adaptative algorithm for sit-to-stand timing detection

A simple wearable device for sit-to-stand timing detection was designed and constructed with rate gyroscopes and accelerometers and a dedicated adaptive algorithm. The method was validated by comparison with optoelectronic equipment. Results from the comparison showed a maximal error always lower than 2.5 x 10(-2) s for start and stop detection.     

A highly stretchable strain sensor based on CNT/graphene/fullerene-SEBS

Recently, highly stretchable strain sensors have attracted considerable attention. Identifying alternatives to sensitive unit materials and flexible substrates is critical in the fabrication of sensors. Herein, a trinary hybrid carbon material consisting of carbon nanotubes (CNTs), graphene, and fullerene was chosen due to its dense interconnections and robust mechanism. Additionally, the cost-effective fabrication of styrene ethylene butylene styrene (SEBS) provides a platform for the strong adhesion of substrates, which contributes to the strong interaction between the substrates and the sensitive unit materials. Furthermore, the intrinsically high elasticity of SEBS allows the sensors to endure large stretching ranges. Owing to the above-mentioned merits, the fabricated sensor based on CNT/graphene/fullerene-SEBS has a high conductivity of 5.179 S m⁻¹, a moderate gauge factor (GF) of 15, an optimum stretching range of 203%, a linearity of 136% (R² = 0.998), and adaptive-rate repeatability, which reveals its potential in the fields of human motion monitoring and scalable applications.

Recently, highly stretchable strain sensors have attracted considerable attention. Identifying alternatives to sensitive unit materials and flexible substrates is critical in the fabrication of sensors.     

Flexible pH sensor based on a conductive PANI membrane for pH monitoring

pH is a critical parameter used to specify the acidity or alkalinity of an aqueous solution in chemistry, food processing, and medical care. In this study, a conductimetric-type micro pH sensor has been achieved using PANI membrane fabricated on a flexible substrate film aiming to monitor wound healing. The sensor is based on the incorporation of a polyaniline (PANI) membrane, interdigital electrode, and polyimide (PI) substrate. PANI was doped with dodecyl benzene sulfonic acid (DBSA) to obtain good conductivity. The electrodes were patterned on the PI film by etching. The contact area between the PANI and interdigital electrodes improves the responsiveness of the pH sensor. A sensitivity of 58.57 mV per pH over the entire pH range from 5.45 to 8.62 was obtained experimentally, along with a superior repeatability of 8% FS (full scale) and a temperature drift of 6.8% FS. This micro flexible pH sensor aims to monitor the pH value of wound healing, which also facilitates the realization of online monitoring of the pH for telemedicine, food safety, and home health care.

A conductimetric flexible film pH sensor working in sensing materials of PANI membrane was developed for clinic wound monitoring.     

A self-supported electrode for supercapacitors based on nanocellulose/multi-walled carbon nanotubes/polypyrrole composite

A robust self-supported electrode based on nanocellulose fibers (CNF), multi-walled carbon nanotubes (CNT), and polypyrrole (PPy) was prepared by a facile combination of ultrasonic dispersion and consequent in situ polymerization. In addition, the feasibility of utilizing this ternary composite as an electrode for supercapacitors was studied. The results revealed that the obtained CNF/CNT/PPy composite exhibited a large specific capacitance of 200.8 F g⁻¹ at 0.5 A g⁻¹. Equally important, the electrode capacitance retained about 90% of its initial value after 5000 charge/discharge cycles at a current density of 1 A g⁻¹, which thus demonstrated its excellent cycling stability. The simple integration route and outstanding electrochemical properties distinguish this new composite as a prospective candidate for use as a high-performance electrode in supercapacitors.

A robust self-supported electrode was prepared by a facile combination of ultrasonic dispersion and consequent in situ polymerization.     

Construction of a non-enzymatic electrochemical sensor based on graphitic carbon nitride nanosheets for sensitive detection of procalcitonin

In this study, we established a label free and ultrasensitive electrochemical sensor based on graphitic nitride nanosheets (g-C₃N₄ NS) for procalcitonin (PCT) detection. Firstly, an easy-to-prepare and well-conducting g-C₃N₄ NS was synthesized. Next the g-C₃N₄ NS was immobilized on the electrode surface by π–π stacking, and further used to anchor the specific recognition peptide (PP). The surface morphology and structure after g-C₃N₄ NS and PP modification was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and electrochemistry. The sensing property of this sensor was evaluated by differential pulse voltammetry (DPV) and showed a detection sensitivity with a dynamic range from 0.15 to 11.7 fg mL⁻¹ with a low limit of detection (LOD) of 0.11 fg mL⁻¹. Besides, the electrochemical biosensor was successfully used to detect PCT in human serum samples, and the results suggest its potential use in clinical application.

A simple and ultra-sensitive electrochemical biosensor based on graphitic carbon nitride nanosheets (g-C₃N₄ NS) was developed for the detection of PCT. This sensor presented excellent sensing performance and demonstrates potential for clinical application.     

Highly sensitive strain sensors based on hollow packaged silver nanoparticle-decorated three-dimensional graphene foams for wearable electronics

Flexible strain sensors possess a great potential for applications in wearable electronic devices for human motion detection, health monitoring, implantable medical devices and so on. However, the development of highly sensitive strain sensors remains a challenge in the field of wearable electronics. Herein, we prepared a highly sensitive strain sensor, which was composed of a three-dimensional reduced graphene oxide foam decorated with silver nanoparticles (Ag NPs) to enhance the conductivity. Then, half-cured polydimethylsiloxane was employed to get a special “hollow packaged” structure. Thanks to the synergistic conductive effect of Ag NPs and the reduced graphene oxide flakes as well as the special “hollow packaged” structure, the as-prepared flexible strain sensor not only possessed a dramatic gauge factor of 1588 (at 50% sensing strain), but also exhibited high stability in 500 cycles of 30% strain. The mechanism of the enhancement of the sensitivity with the special “hollow packaged” structure was discussed as well. Meanwhile, the detection of the bending and rotation of wrists and the bending of fingers and arms was demonstrated, showing attractiveness in human motion detection.

Silver nanoparticle-decorated three-dimensional graphene foams were prepared and packaged with half-cured PMDS films, forming a special “hollow packaged” structure that exhibited high sensitivity for wearable strain sensor applications.     

基于多传感器融合的用于脑卒中患者的可穿戴式上肢动作识别系统

目的:研究一种用于脑卒中患者上肢动作康复评估的可穿戴式的基于多传感器融合的上肢动作的自动识别系统。方法:提出一种基于多传感器融合的可穿戴上肢动作识别系统,以实现上肢动作的自动识别。系统硬件包含一个主节点和三个从节点,其中主节点由一个WIFI模块和一个微处理器构成,从节点由一个高灵敏度加速度计和一个微处理器构成。从节点采集上肢动作的加速度信号,传输至主节点,再由主节点的WIFI模块无线传输至PC端。这样的系统硬件具有功耗低、微型化、可拓展性强等特点。系统软件基于Adaboost的动作分类算法,通过分析接收到的上肢动作的加速度信号,自动判断不同的三种上肢动作。结果:系统对三种不同的上肢动作能够实现自动识别,识别准确率高达97.99%。结论:该可穿戴式系统在脑卒中患者上肢动作康复评估中具有良好的应用价值。     

A label-free RTP sensor based on aptamer/quantum dot nanocomposites for cytochrome c detection

Given the outstanding room-temperature phosphorescence (RTP) of Mn–ZnS quantum dots (QDs) and the specific recognition performance of the aptamer, we built phosphorescent composites from aptamers conjugated with polyethyleneimine quantum dots (PEI-QDs) and applied them to cytochrome c (Cyt c) detection. Specifically, QDs/CBA composites were generated from the electrostatic interaction between the positively-charged PEI-QDs and the negatively-charged Cyt c binding aptamer (CBA). With the presence of Cyt c, the Cyt c can specifically bind with the QDs/CBA composites, and quench the RTP of QDs through photoinduced electron-transfer (PIET). Thereby, an optical biosensor for Cyt c detection was built, which had a detection range of 0.166–9.96 μM and a detection limit of 0.084 μM. This aptamer-mediated phosphorescent sensor with high specificity and operational simplicity can effectively avoid the interference of scattering light from complex substrates. Our findings offer a new clue for building biosensors based on QDs and aptamers.

In this study, the nanocomposites from polyethyleneimine-capped Mn-doped ZnS QDs (PEI-QDs) and Cyt c binding aptamer (CBA) were prepared and used as Cyt c RTP sensors..     

An electrochemical sensor based on a MOF/ZnO composite for the highly sensitive detection of Cu(ii) in river water samples

Cu(ii) ions are one of the most common forms of copper present in water and can cause bioaccumulation and toxicity in the human body; therefore, sensitive and selective detection methods are required. Herein, a copper ion sensor based on a UiO-66-NH₂/ZnO composite material is proposed. The UiO-66-NH₂/ZnO nanocomposite was prepared by an ultrasonic mixing method. The morphology and structure of the nanocomposite were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The sensitivity to Cu(ii) is 6.46 μA μM⁻¹ and the detection limit is 0.01435 μM. The composite material is rich in –OH and –NH₂ groups, which are active sites for Cu(ii) adsorption. The UiO-66-NH₂/ZnO-modified electrode has good repeatability and anti-interference ability. The sensor was successfully used for the determination of Cu(ii) in an actual water sample.

Cu(ii) ions are one of the most common forms of copper present in water and can cause bioaccumulation and toxicity in the human body; therefore, sensitive and selective detection methods are required.     

Highly dispersed and stable nano zero-valent iron doped electrospun carbon nanofiber composite for aqueous hexavalent chromium removal

In this work, a nZVI doped electrospun carbon nanofiber (nZVI-CNF) composite was prepared and applied for aqueous hexavalent chromium (Cr(vi)) removal. Firstly, FeCl₃/PAN nanofibers were prepared by a simple electrospinning method; Then, nZVI-CNFs were obtained by carbonization of FeCl₃/PAN nanofibers at 800 °C. The surface morphology and internal structure of nZVI-CNFs were characterized by SEM and TEM, showing that the uniformly dispersed nZVI particles were well integrated into the carbon layer structure. The Cr(vi) removal efficiency of nZVI-CNFs was 91.5% with a Cr(vi) concentration of 10 mg L⁻¹ and the mechanism was further studied by XRD and XPS. Meanwhile, the nZVI-CNFs exhibited good stability over a wide range of pH values from 4–8 and a long time placement stability. Furthermore, nZVI-CNFs can be used as a filter membrane for continuous treatment of wastewater, suggesting great potential for practical application.

Improving the dispersion and stability of nano zero-valent iron (nZVI) is very important for its practical application.     

Chronoampermetric detection of enzymatic glucose sensor based on doped polyindole/MWCNT composites modified onto screen-printed carbon electrode as portable sensing device for diabetes

Doped-polyindole (dPIn) mixed with multi-walled carbon nanotubes (MWCNTs) were coated on a screen-printed electrode to improve the electroactive surface area and current response of the chronoamperometric enzymatic glucose sensor. Glucose oxidase mixed with chitosan (CHI-GOx) was immobilized on the electrode. (3-Aminopropyl) triethoxysilane (APTES) was used as a linker between the CHI-GOx and the dPIn. The current response of the glucose sensor increased with increasing glucose concentration according to a power law relation. The sensitivity of the CHI-GOx/APTES/dPIn was 55.7 μA mM⁻¹ cm⁻² with an LOD (limit of detection) of 0.01 mM, where the detectable glucose concentration range was 0.01–50 mM. The sensitivity of the CHI-GOx/APTES/1.5%MWCNT-dPIn was 182.9 μA mM⁻¹ cm⁻² with an LOD of 0.01 mM, where the detectable glucose concentration range was 0.01–100 mM. The detectable concentration ranges of glucose well cover the glucose concentrations in urine and blood. The fabricated enzymatic glucose sensors showed high stability during a storage period of four weeks and high selectivity relative to other interferences. Moreover, the sensor was successfully demonstrated as a continuous or step-wise glucose monitoring device. The preparation method employed here was facile and suitable for large quantity production. The glucose sensor fabricated here, consisting of the three-electrode cell of SPCE, were simple to use for glucose detection. Thus, it is promising to use as a prototype for real glucose monitoring for diabetic patients in the future.

The enzymatic glucose sensor based on a dPIn and dPIn/MWCNT modified screen-printed carbon electrode with a facile method possessed good glucose response. The detectable glucose concentration range covers well the glucose concentrations in urine and blood.     

Sensitive electrochemical sensor based on poly(l-glutamic acid)/graphene oxide composite material for simultaneous detection of heavy metal ions

Heavy metal pollution can be toxic to humans and wildlife, thus it is of great significance to develop rapid and sensitive methods to detect heavy metal ions. Here, a novel type of electrochemical sensor for the simultaneous detection of heavy metal ions has been prepared by using poly(l-glutamic acid) (PGA) and graphene oxide (GO) composite materials to modify the glassy carbon electrode (GCE). Due to the good binding properties of poly(l-glutamic acid) (PGA) for the heavy metal ions (such as Cu²⁺, Cd²⁺, and Hg²⁺) as well as good electron conductivity of graphene oxide (GO), the heavy metal ions, Cu²⁺, Cd²⁺, and Hg²⁺ in aqueous solution can be accurately detected by using differential pulse anodic stripping voltammetry method (DPASV). Under the optimized experiment conditions, the modified GCE shows excellent electrochemical performance toward Cu²⁺, Cd²⁺, and Hg²⁺, and the linear range of PG/GCE for Cu²⁺, Cd²⁺, and Hg²⁺ is 0.25–5.5 μM, and the limits of detection (LODs, S/N ≥ 3) Cu²⁺, Cd²⁺, and Hg²⁺ are estimated to be 0.024 μM, 0.015 μM and 0.032 μM, respectively. Moreover, the modified GCE is successfully applied to the determination of Cu²⁺, Cd²⁺, and Hg²⁺ in real samples. All obtained results show that the modified electrode not only has the advantages of simple preparation, high sensitivity, and good stability, but also can be applied in the field of heavy metal ion detection.

A novel electrochemical sensor with high stability and good reproducibility for the simultaneous detection of heavy metal ions was prepared by using PGA/GO to modify the GCE, showing high sensitivity of superior to most of the reported values.     

Turn-on signal fluorescence sensor based on DNA derived bio-dots/polydopamine nanoparticles for the detection of glutathione

A convenient, fast, sensitive and highly selective fluorescence sensor for the detection of glutathione (GSH) based on DNA derived bio-dots (DNA bio-dots)/polydopamine (PDA) nanoparticles was constructed. The fluorescent switch of DNA bio-dots was induced to turn off because of fluorescence resonance energy transfer (FRET) reactions between DNA bio-dots and PDA. The presence of GSH blocked the spontaneous oxidative polymerization of dopamine (DA) to PDA, leading the fluorescent switch of DNA bio-dots to be “turned on”. The degree of fluorescence recovery of DNA bio-dots is linearly correlated with the concentration of GSH within the range of 1.00–100 μmol L⁻¹, and the limit of detection (LOD) is 0.31 μmol L⁻¹ (S/N = 3, n = 9). Furthermore, the fluorescence sensor was successfully used to quantify GSH in human urine and glutathione whitening power, indicating the fluorescence sensor has potential in the detection of human body fluids and pharmaceutical preparations.

The turn-on fluorescence signal mechanism for detection of GSH.