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Microfluidics Temperature Compensating and Monitoring Based on Liquid Metal Heat Transfer

MICROMACHINES 2022年第5期13卷 792-792页

作者： Meng, Jiyu Yu, Chengzhuang Li, Shanshan Wei, Chunyang Dai, Shijie Li, Hui Li, Junwei Hebei Univ Technol Sch Mech Engn Hebei Key Lab Smart Sensing & Human Robot Interac Tianjin 300130 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300401 Peoples R China Hebei Univ Technol Sch Hlth Sci & Biomed Engn Tianjin 300401 Peoples R China

Microfluidic devices offer excellent heat transfer, enabling the biochemical reactions to be more efficient. However, the precision of temperature sensing and control of microfluids is limited by the size effect. Here in this work, the relationship between the microfluids and the glass substrate of a typical microfluidic device is investigated. With an intelligent structure design and liquid metal, we demonstrated that a millimeter-scale industrial temperature sensor could be utilized for temperature sensing of micro-scale fluids. We proposed a heat transfer model based on this design, where the local correlations between the macro-scale temperature sensor and the micro-scale fluids were investigated. As a demonstration, a set of temperature-sensitive nucleic acid amplification tests were taken to show the precision of temperature control for micro-scale reagents. Comparations of theoretical and experimental data further verify the effectiveness of our heat transfer model. With the presented compensation approach, the slight fluorescent intensity changes caused by isothermal amplification polymerase chain reaction (PCR) temperature could be distinguished. For instance, the probability distribution plots of fluorescent intensity are significant from each other, even if the amplification temperature has a difference of 1 degrees C. Thus, this method may serve as a universal approach for micro-macro interface sensing and is helpful beyond microfluidic applications.

关键词： heat transfer microfluidics liquid metal measurement temperature monitoring PCR

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Tailorable Capacitive Tactile Sensor Based on Stretchable and Dissolvable Porous Silver Nanowire/Polyvinyl Alcohol Nanocomposite Hydrogel for Wearable human Motion Detection

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ADVANCED MATERIALS INTERFACES 2021年第20期8卷

作者： Wang, Peng Li, Guoxian Liu, Jun Hou, Zhanrui Meng, Chuizhou Guo, Shijie Liu, Changhong Fan, Shoushan Hebei Univ Technol Sch Mech Engn Hebei Key Lab Smart Sensing & Human Robot Interac State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300401 Peoples R China Tsinghua Univ Dept Phys Tsinghua Foxconn Nanotechnol Res Ctr Beijing 100084 Peoples R China

Recently, advanced flexible tactile sensors have been widely studied for human motion detection, which is an essential part of human healthcare monitoring. New types of materials with novel composition and structures play a significant role in sensing performance improvement. Herein, a stretchable and dissolvable porous silver nanowire (Ag NW)/polyvinyl alcohol (PVA) nanocomposite hydrogel is fabricated through a facile foaming and freezing-thawing combined approach. The PVA gel is foamed with lots of tailorable micropores to achieve much enhanced stretchability and compressibility. Ag NWs are uniformly embedded inside PVA matrix to increase the permittivity upon introduction of numerous microcapacitors. Incorporated with carbon nanotube network electrodes, a capacitive tactile sensor is developed with high sensitivity (1.9 kPa(-1)), wide detection range (250 kPa), quick response time (25 ms), and remarkable stability over 10 000 loading/unloading cycles. Wearable sensing demonstration of detecting various human motions is performed. The hydrogel-based sensor can be dissolved in hot water within minutes with recycling use of electrode material, which is environmentally friendly. A large-area integrated sensor sheet can be made upon one fabrication process followed by cut into small sensor devices with desired shapes, indicating potential customized mass production. The proposed microporous nanocomposite hydrogel-based sensor is promising in wearable sensing applications.

关键词： hydrogel-based sensors nanocomposite dielectrics polyvinyl alcohol hydrogels silver nanowires stretchable sensors tactile sensors

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A Cost-Effective Nucleic Acid Detection System Using a Portable Microscopic Device

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MICROMACHINES 2022年第6期13卷 869-869页

作者： Yu, Chengzhuang Li, Shanshan Wei, Chunyang Dai, Shijie Liang, Xinyi Li, Junwei Hebei Univ Technol Sch Mech Engn Hebei Key Lab Smart Sensing & Human Robot Interac Tianjin 300130 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300130 Peoples R China Hebei Univ Technol Inst Biophys Sch Hlth Sci & Biomed Engn Tianjin Peoples R China

A fluorescence microscope is one of the most important tools for biomedical research and laboratory diagnosis. However, its high cost and bulky size hinder the application of laboratory microscopes in space-limited and low-resource applications. Here, in this work, we proposed a portable and cost-effective fluorescence microscope. Assembled from a set of 3D print components and a webcam, it consists of a three-degree-of-freedom sliding platform and a microscopic imaging system. The microscope is capable of bright-field and fluorescence imaging with micron-level resolution. The resolution and field of view of the microscope were evaluated. Compared with a laboratory-grade inverted fluorescence microscope, the portable microscope shows satisfactory performance, both in the bright-field and fluorescence mode. From the configurations of local resources, the microscope costs around USD 100 to assemble. To demonstrate the capability of the portable fluorescence microscope, we proposed a quantitative polymerase chain reaction experiment for meat product authenticating applications. The portable and low-cost microscope platform demonstrates the benefits in space-constrained environments and shows high potential in telemedicine, point-of-care testing, and more.

关键词： portable fluorescence microscope meat products authenticating

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

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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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Thorax Dynamic Modeling and Biomechanical Analysis of Chest Breathing in Supine Lying Position

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JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 2022年第10期144卷 101004-101004页

作者： Zhao, Xingli Guo, Shijie Xiao, Sen Song, Yao Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equip 81 Dingzigu Rd Tianjin 300131 Peoples R China Hebei Univ Technol Hebei Key Lab Robot Sensing & Human Robot Interac 81 Dingzigu Rd Tianjin 300131 Peoples R China Hebei Univ Technol Sch Mech Engn 81 Dingzigu Rd Tianjin 300131 Peoples R China

During respiration, the expansion and contraction of the chest and abdomen are coupled with each other, presenting a complex torso movement pattern. A finite element (FE) model of chest breathing based on the HUMOS2 human body model was developed. One-dimensional muscle units with active contraction functions were incorporated into the model based on Hill's active muscle model so as to generate muscle contraction forces that can change over time. The model was validated by comparing it to the surface displacement of the chest and abdomen during respiration. Then, the mechanism of the coupled motion of the chest and abdomen was analyzed. The analyses revealed that since the abdominal wall muscles are connected to the lower edge of the rib cage through tendons, the movement of the rib cage may cause the abdominal wall muscles to be stretched in both horizontal and vertical in a supine position. The anteroposterior and the right-left diameters of the chest will increase at inspiration, while the right-left diameter of the abdomen will decrease even though the anteroposterior diameter of the abdomen increases. The external intercostal muscles at different regions had different effects on the motion of the ribs during respiration. In particular, the external intercostal muscles at the lateral region had a larger effect on pump handle movement than bucket handle movement, and the external intercostal muscles at the dorsal region had a greater influence on bucket handle movement than pump handle movement.

关键词： respiratory biomechanics surface displacement active muscle model rib cage motion

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A droplet-based multivolume microfluidic device for digital polymerase chain reaction

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SENSORS AND ACTUATORS B-CHEMICAL 2022年第0期371卷

作者： Wei, Chunyang Yu, Chengzhuang Li, Shanshan Meng, Jiyu Li, Tiejun Cheng, Jingmeng Li, Junwei Hebei Univ Technol Sch Mech Engn Hebei Key Lab Robot Sensing & Human robot Interact Tianjin 300132 Peoples R China Hebei Univ Technol State Key Lab Reliabil & Intelligence Elect Equipm Tianjin 300130 Peoples R China Hebei Univ Sci & Technol Sch Mech Engn Shijiazhuang 050091 Peoples R China Hebei Univ Technol Inst Biophys Sch Hlth Sci & Biomed Engn Tianjin 300401 Peoples R China Hebei Univ Technol Dept Comp Sci & Elect Engn Langfang 065000 Peoples R China

Digital PCR plays an essential role in detecting and quantifying nucleic acid targets. At the same time, there are still challenges in its applications, including reduction of cost, simplification of operations, and system miniaturization. This work proposes a droplet-based multivolume microfluidic device for easy-to-operate and integrated droplet digital PCR (ddPCR). With an "asymmetrical droplet-splitting" microstructure, we have successfully prepared both small and big droplets within the same main channel of the microfluidic chip. With the size of (59.1 +/- 2.2) mu m and (106.3 +/- 3.9) mu m in diameter, about 30,000 droplets are produced for multi-volume ddPCR, and thus to perform a dynamic range of over 10(4) for DNA molecule quantification. The chip integrates droplet generation, droplet array self-assembly, droplet dPCR, and fluorescence detection on a single device. The quantitative capability of the ddPCR chip was evaluated by measuring template DNA at concentrations from 20 to 12,500 *** L-1. Benefiting from the characteristics of the wide dynamic range (10 similar to 10(4) *** L-1), easy operation, and miniaturization, the proposed ddPCR device is expected to be used in applications involving DNA molecule quantification, including diagnosis of genetic disease, single-cell gene expression, and other biomedical fields.

关键词： Digital PCR Microfluidics Multivolume droplets Flexibility Miniaturization High dynamic range

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Pressure-driven dynamical microfluidic pumping system for droplet production

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JOURNAL OF INSTRUMENTATION 2022年第10期17卷 P10038页

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

Compact and affordable microfluidic pumping is critical for point-of-care applications. Here we proposed a data driven dynamical system to build up a pressure-driven microfluidic pump with a small budget. Firstly, a precision flow sensor is required to obtain the dynamic flow rates as the responses to the driven pressures. Then the flow rate dataset under varying operation pressures is used for data training and model-based system identification. With a first-order or second-order transfer function model, the specifications of pressure-driven microfluidic pumping system are analyzed by the model-based system identification algorithm. Also, all the specifications including the gain, time constant, natural frequency, and damping ratio are updated online as new test data are introduced from more experimental trials. To perform a non-bulky design purpose, the data training system identification is taken on a commercial smartphone. Once the training performance is satisfied, the pressure-driven system could be operated without any flow sensors. The system is used for two-phase flow controls as a demonstration, showing a rapid response of pumping. Dynamic characteristics and the effects of flow resistance on the pumping performance are analyzed to verify its suitability for a wide range of microfluidic applications.

关键词： Control and monitor systems online Counting gases and liquids Point-of-care devices

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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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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 laser-scribed wearable strain sensing system powered by an integrated rechargeable thin-film zinc-air battery for a long-time continuous healthcare monitoring

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NANO ENERGY 2022年第0期101卷

作者： Chen, Xue Hou, Zhanrui Li, Guoxian Yu, Wei Xue, Ye Niu, Guangyu Xin, Mingyang Yang, Li Meng, Chuizhou Guo, Shijie Hebei Univ Technol Sch Elect Engn State Key Lab Reliabil & Intelligence Elect Equip Key Lab Bioelectromagnet & Neuroengn Hebei Prov Tianjin 300130 Peoples R China Hebei Univ Technol Sch Mech Engn State Key Lab Reliabil & Intelligence Elect Equip Hebei Key Lab Smart Sensing & Human Robot Interac Tianjin 300401 Peoples R China Hebei Univ Technol Sch Hlth Sci & Biomed Engn State Key Lab Reliabil & Intelligence Elect Equip Tianjin 300130 Peoples R China Hebei Univ Technol Dept Architecture & Art Tianjin 300130 Peoples R China

Wearable sensors with long cruising times without the need for an external wire-connected power supply are urgently required for a continuous physiological signal monitoring. Herein, we report the design and fabrication of a wearable all-in-one sensing system that integrates a sensitive strain sensor and a rechargeable zinc-air battery on the same laser-induced graphene (LIG) platform. The sensing electrode of the strain sensor, the catalytic air electrode of the zinc-air battery and the interconnection lines between the two are simultaneously fabricated through the same laser-scribing process on polyimide (PI) followed by pattern transfer to a flexible and stretchable polydimethylsiloxane (PDMS) substrate. In the sensor, the conductive porous LIG exhibits a high gauge factor (similar to 2710.95), a wide detection range (similar to 40%), and a well cyclic loading-unloading stability (>20,000 cycles). In the zinc-air battery, Co3O4 nanoparticles are in-situ laser-sintered on LIG to form an excellent electrode/electrolyte/air three-phased interfacing structure for a high catalytic performance, and a moisturized tetraethyl ammonium hydroxide (TEAOH)-KOH/polyvinyl alcohol (PVA) gel electrolyte tightly binds the Co3O4/LIG air electrode and zinc foil electrode together into an integrate thin-film energy device, which provides a high open-circuit voltage (similar to 1.39 V) and a high specific capacity (712 mAh g(-1) at 0.2 mA cm(-2)). For a proof-of-concept, an intelligent wristband based on the sensing system was fabricated and worn on the wearer's wrist for a long-time continuous pulse monitoring of up to 10 h. The health state of the wearer can be depicted upon the acquired pulse waveforms. The developed LIG-based sensing system with a high internal powering capability will be promising in wearable sensing applications.

关键词： Laser-induced graphene (LIG) All-in-one integrated system Flexible strain sensor Rechargeable zinc-air battery Gel polymer electrolyte

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