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Rapid Microfluidic Mixing Method Based on Droplet Rotation Due to PDMS Deformation

MICROMACHINES 2021年第8期12卷 901-901页

作者： Wei, Chunyang Yu, Chengzhuang Li, Shanshan Pan, Feng Li, Tiejun Wang, Zichao Li, Junwei Hebei Univ Technol Sch Mech Engn Hebei Key Lab Robot Sensing & Human Robot Interac Tianjin 300132 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300130 Peoples R China Jiangsu Key Lab Adv Food Mfg Equipment & Technol Wuxi 214122 Jiangsu Peoples R China Hebei Univ Technol Sch Sci Inst Biophys Tianjin 300401 Peoples R China Hebei Univ Technol Dept Comp Sci & Elect Engn Langfang 065000 Peoples R China

Droplet-based micromixers have shown great prospects in chemical synthesis, pharmacology, biologics, and diagnostics. When compared with the active method, passive micromixer is widely used because it relies on the droplet movement in the microchannel without extra energy, which is more concise and easier to operate. Here we present a droplet rotation-based microfluidic mixer that allows rapid mixing within individual droplets efficiently. PDMS deformation is used to construct subsidence on the roof of the microchannel, which can deviate the trajectory of droplets. Thus, the droplet shows a rotation behavior due to the non-uniform distribution of the flow field, which can introduce turbulence and induce cross-flow enhancing 3D mixing inside the droplet, achieving rapid and homogenous fluid mixing. In order to evaluate the performance of the droplet rotation-based microfluidic mixer, droplets with highly viscous fluid (60% w/w PEGDA solution) were generated, half of which was seeded with fluorescent dye for imaging. Mixing efficiency was quantified using the mixing index (MI), which shows as high as 92% mixing index was achieved within 12 mm traveling. Here in this work, it has been demonstrated that the microfluidic mixing method based on the droplet rotation has shown the advantages of low-cost, easy to operate, and high mixing efficiency. It is expected to find wide applications in the field of pharmaceutics, chemical synthesis, and biologics.

关键词： microfluidics mixing droplet rotation PDMS deformation

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Graph attention mechanism with global contextual information for multi-label image recognition

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JOURNAL OF ELECTRONIC IMAGING 2021年第6期30卷 063031-063031页

作者： Ban, Xiaoxiao Li, Peihua Wang, Qilong Zhou, Shoujun Guo, Shijie Wang, Yuanquan Hebei Univ Technol Sch Artificial Intelligence Tianjin Peoples R China Dalian Univ Technol Sch Informat & Commun Engn Dalian Liaoning Peoples R China Chinese Acad Sci Shenzhen Inst Adv Technol Shenzhen Peoples R China Hebei Univ Technol Hebei Key Lab Robot Percept & Human Robot Interac Tianjin Peoples R China

Recent works have shown that multi-label image recognition is still a challenging task in computer vision due to the complicatedness and diversity of multi-label images. However, the existing works ignore the co-occurrence correlation and global contextual information between image space and objects. We present a model to solve these problems. On the one hand, we devise the graph attention mechanism to compute the hidden representations of different categories in multi-label images. It can specify different weights to different neighbor objects and well model the label dependency. On the other hand, we iterate the global contextual information by the second-order covariance pooling to enhance nonlinear modeling capability and use basic residual network to extract features. The proposed model is thoroughly evaluated on PASCAL VOC 2007 and MS-COCO datasets. Compared with classical ML-GCN, the model can better combine the image features and label embedding. Meanwhile, experiments show that it outperforms the state-of-the-art methods such as residual multi-layer perception, EfficientNet, and vision transformer. (C) 2021 SPIE and IS&T

关键词： deep learning multi-label modeling attention mechanism high-order statistic

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Easy-to-Operate Co-Flow Step Emulsification Device for High-Throughput Three-Dimensional Cell Culture

BIOSENSORS-BASEL

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BIOSENSORS-BASEL 2022年第5期12卷 350页

作者： Wei, Chunyang Yu, Chengzhuang Li, Shanshan Li, Tiejun Meng, Jiyu Li, Junwei Hebei Univ Technol Sch Mech Engn Hebei Key Lab Robot Sensing & Human Robot Interac Tianjin 300132 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300130 Peoples R China Jiangnan Univ Jiangsu Key Lab Adv Food Mfg Equipment & Technol Wuxi 214122 Jiangsu Peoples R China Hebei Univ Technol Sch Hlth Sci & Biomed Engn Inst Biophys Tianjin 300401 Peoples R China Hebei Univ Technol Dept Comp Sci & Elect Engn Langfang 065000 Peoples R China

Cell culture plays an essential role in tissue engineering and high-throughput drug screening. Compared with two-dimensional (2D) in vitro culture, three-dimensional (3D) in vitro culture can mimic cells in vivo more accurately, including complex cellular organizations, heterogeneity, and cell-extracellular matrix (ECM) interactions. This article presents a droplet-based microfluidic chip that integrates cell distribution, 3D in vitro cell culture, and in situ cell monitoring in a single device. Using the microfluidic "co-flow step emulsification" approach, we have successfully prepared close-packed droplet arrays with an ultra-high-volume fraction (72%) which can prevent cells from adhering to the chip surface so as to achieve a 3D cell culture and make scalable and high-throughput cell culture possible. The proposed device could produce droplets from 55.29 +/- 1.52 to 95.64 +/- 3.35 p.m, enabling the diverse encapsulation of cells of different sizes and quantities. Furthermore, the cost for each microfluidic CFSE chip is approximately USD 3, making it a low-cost approach for 3D cell culture. The proposed device is successfully applied in the 3D culture of saccharomyces cerevisiae cells with an occurrence rate for proliferation of 80.34 +/- 3.77%. With low-cost, easy-to-operate, high-throughput, and miniaturization characteristics, the proposed device meets the requirements for 3D in vitro cell culture and is expected to be applied in biological fields such as drug toxicology and pharmacokinetics.

关键词： microfluidics droplet arrays 3D cell culture co-flow step emulsification lab on a chip

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Polydopamine functionalized MXene for chemiresistive gas sensing: partial oxidation and optimized chemical state pinning

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SENSORS AND ACTUATORS B-CHEMICAL 2023年第1期386卷

作者： Zhang, Ruiguang Yang, Li Liu, Guoqing Yin, Fuxing Yuan, Wenjing Guo, Shijie Hebei Univ Technol Sch Mat Sci & Engn Tianjin 300130 Peoples R China Hebei Univ Technol Sch Mech Engn State Key Lab Reliabil & Intelligence Elect Equipm Hebei Key Lab Smart Sensing & Human Robot Interact Tianjin 300401 Peoples R China

Two-dimensional MXene has been receiving attention for its outstanding properties of intrinsic metallic con-ductivity, high specific surface area and abundant surface terminations, showing great potential in gas sensing. However, it suffers from low sensing response and poor chemical stability. To address these issues, we propose a series of surface treatment to anchor interaction sites onto MXene, and to pin its optimized chemical state. interaction sites including -OH, -NH2, and -O- were functionalized through self-polymerization of dopamine and controlled oxidation of the MXene base. These functionalized groups can interact with gas molecules through hydrogen bonding;besides, multiple Schottky barriers are generated within the sensing layer, thus improving formaldehyde sensing response by over 16-fold in comparison with pristine MXene. This optimized sensing state was further pinned through a hydrophobic treatment, and the composite obtained demonstrated a long-term stability (larger than 25 days) as well as a high sensitivity.

关键词： MXene Gas sensor Surface treatment Pinning strategy

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Random Forest Feature Selection and Back Propagation Neural Network to Detect Fire Using Video

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JOURNAL OF SENSORS 2022年第1期2022卷

作者： Liang, Jin-Xing Zhao, Jian-Fu Sun, Ning Shi, Bao-Jun Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equi Tianjin 300401 Peoples R China Hebei Key Lab Robot Sensing & Human Robot Integra Tianjin 300401 Peoples R China Hebei Univ Technol Sch Mech Engn Tianjin 300401 Peoples R China Sch CITIC Heavy Ind Kaicheng Intelligent Equipmen Tangshan 063000 Peoples R China

As the most common serious disaster, fire may cause a lot of damages. Early detection and treatment of fires are of great significance to ensure public safety and to reduce losses caused by fires. However, traditional fire detectors are facing some focus issues such as low sensitivity and limited detection scenes. To overcome these problems, a video fire detection hybrid method based on random forest (RF) feature selection and back propagation (BP) neural network is proposed. The improved flame color model in RGB and HSI space and the visual background extractor (ViBe) in moving target detection algorithm are used to segment the suspected flame regions. Then, multidimensional features of flames are extracted from the suspected regions, and these extracted features are combined and selected according to the RF feature importance analysis. Finally, a BP neural network model is constructed for multifeature fusion and fire recognition. The test results on several experimental video sets show that the proposed method can effectively avoid feature interference and has an excellent recognition effect on fires in a variety of scenarios. The proposed method is applicable for fire recognition applied in video surveillance and detection robots.

关键词： Decision trees

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Printable, flexible, breathable and sweatproof bifunctional sensors based on an all-nanofiber platform for fully decoupled pressure-temperature sensing application

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CHEMICAL ENGINEERING JOURNAL 2023年第Part1期452卷

作者： Wang, Peng Yu, Wei Li, Guoxian Meng, Chuizhou Guo, Shijie Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equipm Tianjin 300401 Peoples R China Hebei Univ Technol Hebei Key Lab Smart Sensing & Human Robot Interact Tianjin 300401 Peoples R China Hebei Univ Technol Sch Mech Engn Tianjin 300401 Peoples R China

Flexible bifunctional sensors that mimic the function of human skin are essential as they provide critical interacting information with human and environment for intelligentization. However, the problem of the interference between sensing signals from different stimuli and the deficiency of comfortability for a long-time skin-attaching wearing still exist. Herein, we present an ultrathin and flexible bifunctional sensor based on two measurable parameters of pressure-induced supercapacitance and temperature-induced resistance with neglectable crosstalk between the two. The sensor consists of a planar iontronic supercapacitor underneath a serpentine resistor with assembly of total seven layers integrated on an electrospun thermoplastic polyurethane (TPU)-based nanofiber platform. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based sensing electrodes are patterned by a direct ink writing method with addition of graphene nanoflakes and Co3O4 nanoparticles to enhance the sensing performance. A high pressure sensitivity (147.19 kPa-1, 0-7 kPa;4.41 kPa-1, 25-85 kPa) and a high temperature sensitivity (0.040 degrees C-1, 25-50 degrees C;0.002 degrees C-1, 50-100 degrees C) are simultaneously achieved. The sensor also has the advantages of humidity inertness, waterproof ability and air permeability, which is breathable to obtain a wearing comfortability. Decoupled pressure-temperature sensing applications of detecting various subtle pressures by objects of different temperatures are demonstrated in a wireless and real-time mode. The proposed bifunctional sensor shows great potential in wearable healthcare monitoring.

关键词： Bifunctional sensor Flexible pressure-temperature sensing Electrospun nanofibers Breathable Sweatproof

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Flexible, stretchable, breathable and sweatproof all-nanofiber iontronic tactile sensor for continuous and comfortable knee joint motion monitoring

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NANO ENERGY 2022年第PartA期103卷

作者： Wang, Peng Liu, Jun Yu, Wei Li, Guoxian Meng, Chuizhou Guo, Shijie Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equipm Tianjin 300401 Peoples R China Hebei Univ Technol Hebei Key Lab Smart Sensing & Human Robot Interact Tianjin 300401 Peoples R China Hebei Univ Technol Sch Mech Engn Tianjin 300401 Peoples R China

Running improperly for an extended period of time will induce irreversible damage to knee joints, which can bring about excruciating pains to joggers. Wearable sensors for continual knee-monitoring are highly recom-mended. However, conventional flexible sensors built on airtight substrates are inferior in comfort when wearing for lengthy durations. Herein, a highly flexible and stretchable iontronic tactile sensor is developed on an electrospun thermoplastic polyurethane nanofiber platform. The multilayered, intertwined, nanofiber network housing numerous micro-pores/channels endows the sensor with superior air permeability, sweat inertness, thermal dissipation ability, and biocompatibility, which allows for an extended, comfortable wearing experience. Accrediting the supercapacitive sensing mechanism and porous microstructure, a performance exhibiting a high sensitivity, wide detection range, rapid response, excellent stability and repeatability can be achieved. Prag-matically, a knee-sensor prototype was developed and demonstrated running in real-time and continuously: monitoring a single point of pressure with 3 individual sensor units attached to the rim of the knee and mapping the spatial pressure distribution with an array of sensors covering the whole knee. The health status of the knee could be properly diagnosed, which would be useful for warning of potential knee injuries or to better the form of exercisers.

关键词： Flexible sensor Iontronic tactile sensor Electrospun nanofibers Breathable Sweatproof Knee joint motion monitoring

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Pressure-Driven Micro-Casting for Electrode Fabrication and Its Applications in Wear Grain Detections

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MATERIALS 2019年第22期12卷 3710页

作者： Cheng, E. Xing, Ben Li, Shanshan Yu, Chengzhuang Li, Junwei Wei, Chunyang Cheng, Cheng Hebei Univ Technol Sch Mech Engn Tianjin 300132 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300130 Peoples R China Hebei Univ Technol Hebei Key Lab Robot Sensing & Human Robot Interac Tianjin 300132 Peoples R China Hebei Univ Technol Dept Comp Sci & Elect Engn Langfang 065000 Peoples R China Hebei Univ Technol Sch Sci Inst Biophys Tianjin 300401 Peoples R China Morehead State Univ Sch Engn & Comp Sci Morehead KY 40351 USA

The microelectrode is an essential and vital part in microsensors that are largely used in industrial, chemical, and biological applications. To obtain desired microelectrodes in great quality, it is also of great necessity and significance to develop a robust method to fabricate the microelectrode pattern. This work developed a four-terminal differential microelectrode that aims at recognizing microparticles in fluids. This microelectrode pair consisted of a high height-width ratio microelectrode array fabricated using a pre-designed microelectrode pattern (a micro-scale channel) and melted liquid metal. The surface treatment of microelectrodes was also investigated to reveal its impacts on the continuality of melting metal and the quality of the fabricated microelectrode patterns. To evaluate the performance of micro-casting fabricated electrodes, a microfluidic device was packaged using a microelectrode layer and a flow layer. Then impedance cytometer experiments were performed using sample fluids with polymer particles in two different sizes in diameter (5 mu m and 10 mu m). In addition, engine oil was tested on the microelectrodes as complex samples. The number of abrasive particles in the engine oil can be collected from the developed microfluidic device for further analysis.

关键词： microfabrication melting metal surface pretreatment impedance cytometer differential amplifier wear particle detection

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A conformable, durable, adhesive welded fiber mate for on-skin strain sensing

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CHEMICAL ENGINEERING JOURNAL 2023年第1期457卷

作者： Xie, Xia Liu, Guoqing Li, Haixu Yuan, Wenjing Guo, Shijie Hebei Univ Technol Sch Mat Sci & Engn Tianjin Key Lab Mat Laminating Fabricat & Interfac Tianjin 300130 Peoples R China Hebei Univ Technol Sch Mech Engn State Key Lab Reliabil & Intelligence Elect Equipm Hebei Key Lab Smart Sensing & Human Robot Interact Tianjin 300401 Peoples R China

On-skin electronics have been attracting tremendous attentions due to their potential use for continuous, long-term physical movement detection and physiological signal monitoring. However, developing on-skin strain sensors that can be conformally attached to skin with good breathability and adhesion remains a challenge. Here, we present an ultrathin, lightweight, breathable welded fiber mate-based strain sensor that can be conformally adhered to curved human skin through a sacrificial interlayer. The modulus of the fiber mate is similar to human skin, and its thinness and softness lead to minimum mechanical constraints on skin during deformation (0.03 N at 5 % strain). The welded mate sensor exhibits large stretchability (420 %) and sensing durability due to its double-level elastic structure on both polymer chain and fiber chain levels. It can work over a wide temperature range from 0 to 40 degrees C with almost no temperature interference. After patterned into a serpentine geometry, the welded mate can also be used as a stretchable and conformal gas sensor to detect harmful gases with excellent stability against strain interference.

关键词： Welded fiber mate On-skin electronics Strain sensing Gas sensing MXene

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Graphene-wrapped bimetallic nanoparticles bifunctional electrocatalyst for rechargeable Zn-air battery

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JOURNAL OF ELECTROANALYTICAL CHEMISTRY 2022年 927卷 1页

作者： Zhu, Bo Wan, Tongtao Li, Jing Meng, Chuizhou Du, Xiaohang Liu, Guihua Guan, Yuming Hebei Univ Technol Sch Mech Engn State Key Lab Reliabil & Intelligence Elect Equipm Hebei Key Lab Smart Sensing & Human Robot Interact Tianjin 300130 Peoples R China Hebei Univ Technol Sch Chem Engn & Technol Tianjin Key Lab Chem Proc Safety Tianjin 300130 Peoples R China

Developing efficient and stable bifunctional electrocatalysts towards oxygen evolution/reduction reactions (OER/ORR) is both critical and challenging for the application of zinc-air batteries (ZABs). In this work, a reduced graphene oxide-encapsulated, metal-organic framework (MOF)-derived NiCo bimetallic nanoparti-cles-based bifunctional catalyst (NiCo@rGO) was successfully prepared. The intertwining of flaky rGO and MOF derivatives results in a large specific surface area and abundant pore structure, which is favorable for exposure of active catalytic sites and ensures high electronic conductivity of the catalyst at the same time. The cooperation of cobalt and nickel nanoparticles enriches the active centers and increases the intrinsic cat-alytic activity compared with monometallic Co nanoparticles, leading to enhanced catalytic performance. Benefited from the above advantages, NiCo@rGO exhibits efficient catalytic activities with an oxygen reduc-tion half-wave potential of 0.85 V and oxygen evolution overpotential of 460 mV at 10 mA cm-2. Furthermore, the ZABs with NiCo@rGO exhibits a open-circuit voltage of 1.49 V, a peak power density of as high as 110.45 mW cm-2 and excellent stability over 180 h. This contribution paves a practical avenue to construct bimetal-rGO composites for high-performance ZABs.

关键词： Zinc -air battery NiCo nanoparticles Reduced graphene oxide Bifunctional electrocatalyst

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