Showing papers by "Hongyuan Jiang published in 2020"

Continuous microfluidic mixing and the highly controlled nanoparticle synthesis using direct current-induced thermal buoyancy convection

Abstract: We present a flexible and noninvasive approach for efficient continuous micromixing and microreaction based on direct current-induced thermal buoyancy convection in a single microfluidic unit. Theoretically, microfluids in this microsystem are unevenly heated by powering the asymmetrically arranged microheater. The thermal buoyancy convection is then formed to induce microvortices that cause effective fluidic interface disturbance, thereby promoting the diffusion and convective mass transfer. The temperature distribution and the convection flow in the microchip are first characterized and studied, which can be flexibly adjusted by changing the DC voltage. Then the mixing performance of the presented method is validated by joint numerical and experimental analyses. Specifically, at U = 7 V, the mixing efficiencies are higher than 90% as the flow rate is lower than Qv= 600 nL/s. So high-quality chemical or biochemical reactions needing both suitable heating and efficient mixing can be achieved using this method. Finally, as one example, we use this method to synthesize nano-sized cuprous oxide (Cu2O) particles by effectively mixing the Benedict’s solution and glucose buffer. Remarkably, the particle size can be tuned by changing the voltage and the concentration of Benedict’s solution. Therefore, this micromixer can be attractive for diverse applications needing homogeneous sample mixtures.

Three-Fluid Sequential Micromixing-Assisted NanoparticleSynthesis Utilizing Alternating Current Electrothermal Flow

Abstract: Multiple micromixing in a controlled sequence is an essential process for complex chemical synthesis of functional nanoparticles with desired physicochemical properties. Herein, we developed a uniq...

Numerical Simulation and Experimental Validation of Liquid Metal Droplet Formation in a Co-Flowing Capillary Microfluidic Device.

Abstract: A two-phase flow axisymmetric numerical model was proposed to understand liquid metal droplet formation in a co-flowing capillary microfluidics device based on a phase field model. The droplet detachment processes were observed in the experiment and are in good agreement with the simulation method. The effects of the viscosities and flowrates of the continuous phase fluid, interfacial tension as well as the wetting property of the metallic needle against the bulk liquid metal on the droplet formation and production rate were numerically investigated. It was found that the droplet diameter decreased with the increment of the viscosities and flowrates of the outer phase carrier fluid. The dispersed phase fluid with high interfacial tension tended to prolong the time for equilibrium between the viscous drag force and interfacial tension on the liquid–liquid fluid surface, delaying the droplet to be pinched off from the capillary orifice and causing large droplet diameter. Finally, the wetting performance of the metallic needle against the liquid metal was explored. The result indicate that the droplet diameter became less dependent on the contact angle while the size distribution of the liquid metal droplet was affected by their wetting performance. A more hydrophilic wetting performance were expected to prepare liquid metal droplet with more monodispersity. The numerical model and simulation results provide the feasibility of predicting the droplet formation with a high surface tension in a glass capillary microfluidic device.

Flexible Particle Focusing and Switching in Continuous Flow via Controllable Thermal Buoyancy Convection.

Abstract: We present a novel approach that utilizes thermal buoyancy convection to achieve flexible particle focusing and switching in continuous flow of a microfluidic system. In this platform, three strip ...

Combined alternating current electrothermal and dielectrophoresis-induced tunable patterning to actuate on-chip microreactions and switching at a floating electrode

Abstract: A unique platform to fabricate tunable micropatterns at an electrically floating electrode has been developed via an enhanced combination of dielectrophoresis (DEP) and alternating current electrothermal (ACET) processes. The design of the platform uses two pairs of driving electrodes to generate a tunable electric field at a floating electrode, which in turn allows for the formation of patterned cells and fluids with desired features. By regulating the input configuration of the ac signals, yeast cells can be either patterned at the field stagnant region by a synergistic combination of negative DEP and ACET flow, or partially captured at the electrode edges subjected to a strong positive DEP, to form varying cell patterns. Additionally, nanoparticles were used to characterize the ACET-based flow pattern formation. Furthermore, the patterns were successfully exploited as an electrokinetic actuator to actuate continuous droplet switching, fluid mixing and microreactions. Implementing the simultaneous nanoparticle synthesis and guiding demonstrated that the combined field pattern is capable of manipulating both particulate samples and fluids. The proposed micropatterning technique may provide new insights for sample manipulation, on-chip function development and integration with other analytical components (i.e., biochemical sensors, chemical detectors, cell culture bioreactors) owing to a facile operation, easy integration and multifunctionality.

A Routing-Based Repair Method for Digital Microfluidic Biochips Based on an Improved Dijkstra and Improved Particle Swarm Optimization Algorithm.

Abstract: Digital microfluidic biochips (DMFBs) are attractive instruments for obtaining modern molecular biology and chemical measurements. Due to the increasingly complex measurements carried out on a DMFB, such chips are more prone to failure. To compensate for the shortcomings of the module-based DMFB, this paper proposes a routing-based fault repair method. The routing-based synthesis methodology ensures a much higher chip utilization factor by removing the virtual modules on the chip, as well as removing the extra electrodes needed as guard cells. In this paper, the routing problem is identified as a dynamic path-planning problem and mixed path design problem under certain constraints, and an improved Dijkstra and improved particle swarm optimization (ID-IPSO) algorithm is proposed. By introducing a cost function into the Dijkstra algorithm, the path-planning problem under dynamic obstacles is solved, and the problem of mixed path design is solved by redefining the position and velocity vectors of the particle swarm optimization. The ID-IPSO routing-based fault repair method is applied to a multibody fluid detection experiment. The proposed design method has a stronger optimization ability than the greedy algorithm. The algorithm is applied to , , and fault-free chips. The proposed ID-IPSO routing-based chip design method saves 13.9%, 14.3%, and 14.5% of the experiment completion time compared with the greedy algorithm. Compared with a modular fault repair method based on the genetic algorithm, the ID-IPSO routing-based fault repair method has greater advantages and can save 39.3% of the completion time on average in the completion of complex experiments. When the ratio of faulty electrodes is less than 12% and 23%, the modular and ID-IPSO routing-based fault repair methods, respectively, can guarantee a 100% failure repair rate. The utilization rate of the electrodes is 18% higher than that of the modular method, and the average electrode usage time is 17%. Therefore, the ID-IPSO routing-based fault repair method can accommodate more faulty electrodes for the same fault repair rate; the experiment completion time is shorter, the average number of electrodes is lower, and the security performance is better.

Fabrication of syntactic foam fillers via manipulation of on-chip quasi concentric nanoparticle-shelled droplet templates.

Abstract: Syntactic foams with fly ash cenospheres or commercial microballoons as fillers have been widely used in various applications ranging from aerospace to marine fields and the automotive industry. However, these two extensively adopted fillers possess multiple shortcomings, such as variations in the composition, material degeneration and distinct structural heterogeneity, which will inevitably hamper accurate prediction of the structure-property relationship and the corresponding design of the syntactic foams, reducing material utilization. Here, we present a microfluidic-based approach integrated with a subsequent heat treatment process to engineer syntactic foam fillers with a predefined composition, specified dimensional scope and reduced structural heterogeneity. These fillers are fully guaranteed by the synergy of the flexible and controllable generation of droplet templates with hydrodynamic regulation and rational selection of the nanoparticle dynamic response with respect to the heating temperature. In addition, two distinct surface morphologies have been observed with a temperature demarcation point of 1473 K, further endowing the fillers with multiplicity and optionality, simultaneously laying the foundation to regulate the properties of the syntactic foams through the diversity of the filler selection. Then, we fabricated a syntactic foam specimen by mold casting, and the integrity of the fillers inside was verified using an elaborate buoyancy comparison experiment, exhibiting its potential value in lightweight related applications. As the fillers derived from our approach show significant advantages over conventional ones, they will provide considerable benefits for the regulation and improvement of syntactic foam fillers in many practical applications.

Versatile Movements of Liquid Metal Droplet under Electrostatic Actuation in Alkaline Solutions.

Abstract: The gallium-based eutectic liquid metal alloys exhibit unique properties of deformability, excellent electrical conductivity and low vapour pressure. The liquid metal-based circuits’ element or actuator have drawn considerable attention in stretchable electronics and microelectromechanical (MEMS) actuators. Yet, the motion of the liquid metal within the electrolyte needs to be precisely regulated to satisfy application requirements. Herein, we investigated the locomotion of liquid metal within the alkaline aqueous solution under electrostatic actuation. The relationship between the travelling speed of the liquid metal slug and the relative influential parameters, such as the voltage amplitude and frequencies of the applied electric field, electrolyte concentration, electrodes distance and the liquid metal volume, were experimentally characterized. A travelling speed up to 20.33 mm/s was obtained at the applied voltage of 4 Vpp at 150 Hz at 6 V DC offset. Finally, the frequency-dependent liquid metal marble movements were demonstrated, namely oscillation and forward locomotion while oscillating. The oscillation frequency was determined by the frequency of the applied alternate current (AC) signal. The remarkable transportation and oscillating characteristic of the liquid metal marble under the electrostatic actuation may present potentials towards the development of flexible electronics and reconfigurable structures.

Piezoelectric Performance of a Symmetrical Ring-Shaped Piezoelectric Energy Harvester Using PZT-5H under a Temperature Gradient.

Abstract: With the rapid development of microelectronics technology, low-power electronic sensors have been widely applied in many fields, such as Internet of Things, aerospace, and so on In this paper, a symmetrical ring-shaped piezoelectric energy harvester (SR-PEH) is designed to provide energy for the sensor to detect the ambient temperature The finite element method is used by utilizing software COMSOL 54, and the electromechanical coupling model of the piezoelectric cantilever is established The output performance equations are proposed; the microelectromechanical system (MEMS) integration process of the SR-PEH, circuit, and sensor is stated; and the changing trend of the output power density is explained from an energy perspective In the logarithmic coordinate system, the results indicate that the output voltage and output power are approximately linear with the temperature when the resistance is constant In addition, the growth rate of the output voltage and output power decreases with an increase of resistance under the condition of constant temperature In addition, with an increase of temperature, the growth rate of the output power is faster than that of the output voltage Furthermore, resistance has a more dramatic effect on the output voltage, whereas temperature has a more significant effect on the output power More importantly, the comparison with the conventional cantilever-shaped piezoelectric energy harvester (CC-PEH) shows that the SR-PEH can improve the output performance and broaden the frequency band