As an accurate 2D/3D fabrication tool,inkjet printing technology has great potential in preparation of micro electronic devices.The morphology of droplets produced by the inkjet printer has a great impact on the accur...As an accurate 2D/3D fabrication tool,inkjet printing technology has great potential in preparation of micro electronic devices.The morphology of droplets produced by the inkjet printer has a great impact on the accuracy of deposition.In this study,the drop-on-demand(DoD)inkjet simulation model was established,and the accuracy of the simulation model was verified by corresponding experiments.The simulation result shows that the velocity of the droplet front and tail,as well as the time to disconnect from the nozzle is mainly affected by density(ρ),viscosity(μ)and surface tension(σ)of droplets.When the liquid filament is about to disconnect from the nozzle,the filament length and filament front velocity are found to have a linear correlation withσ/ρμand ln(ρ/(μσ1/2)).展开更多
The droplet formation dynamics of a Newtonian liquid in a drop-on-demand (DOD) inkjet process is numerically investigated by using a volume-of-fluid (VOF) method. We focus on the nozzle geometry, wettability of the in...The droplet formation dynamics of a Newtonian liquid in a drop-on-demand (DOD) inkjet process is numerically investigated by using a volume-of-fluid (VOF) method. We focus on the nozzle geometry, wettability of the interior surface, and the fluid properties to achieve the stable droplet formation with higher velocity. It is found that a nozzle with contracting angle of 45° generates the most stable and fastest single droplet, which is beneficial for the enhanced printing quality and high-throughput printing rate. For this nozzle with the optimal geometry, we systematically change the wettability of the interior surface, i.e., different contact angles. As the contact angle increases, pinch-off time increases and the droplet speed reduces. Finally, fluids with different properties are investigated to identify the printability range.展开更多
On-demand droplet sorting is extensively applied for the efficient manipulation and genome-wide analysis of individual cells.However,state-of-the-art microfluidic chips for droplet sorting still suffer from low sortin...On-demand droplet sorting is extensively applied for the efficient manipulation and genome-wide analysis of individual cells.However,state-of-the-art microfluidic chips for droplet sorting still suffer from low sorting speeds,sample loss,and labor-intensive preparation procedures.Here,we demonstrate the development of a novel microfluidic chip that integrates droplet generation,on-demand electrostatic droplet charging,and high-throughput sorting.The charging electrode is a copper wire buried above the nozzle of the microchannel,and the deflecting electrode is the phosphate buffered saline in the microchannel,which greatly simplifies the structure and fabrication process of the chip.Moreover,this chip is capable of high-frequency droplet generation and sorting,with a frequency of 11.757 kHz in the drop state.The chip completes the selective charging process via electrostatic induction during droplet generation.On-demand charged microdroplets can arbitrarilymove to specific exit channels in a three-dimensional(3D)-deflected electric field,which can be controlled according to user requirements,and the flux of droplet deflection is thereby significantly enhanced.Furthermore,a lossless modification strategy is presented to improve the accuracy of droplet deflection or harvest rate from 97.49% to 99.38% by monitoring the frequency of droplet generation in real time and feeding it back to the charging signal.This chip has great potential for quantitative processing and analysis of single cells for elucidating cell-to-cell variations.展开更多
To improve the efficiency and fairness of the spectrum allocation for ground communication assisted by unmanned aerial vehicles(UAVs),a joint optimization method for on-demand deployment and spectrum allocation of UAV...To improve the efficiency and fairness of the spectrum allocation for ground communication assisted by unmanned aerial vehicles(UAVs),a joint optimization method for on-demand deployment and spectrum allocation of UAVs is proposed,which is modeled as a mixed-integer non-convex optimization problem(MINCOP).An algorithm to estimate the minimum number of required UAVs is firstly proposed based on the pre-estimation and simulated annealing.The MINCOP is then decomposed into three sub-problems based on the block coordinate descent method,including the spectrum allocation of UAVs,the association between UAVs and ground users,and the deployment of UAVs.Specifically,the optimal spectrum allocation is derived based on the interference mitigation and channel reuse.The association between UAVs and ground users is optimized based on local iterated optimization.A particle-based optimization algorithm is proposed to resolve the subproblem of the UAVs deployment.Simulation results show that the proposed method could effectively improve the minimum transmission rate of UAVs as well as user fairness of spectrum allocation.展开更多
In this study the effects of the actuation waveforms on the droplet generation in a drop-on-demand inkjet printing are studied systematically by numerical simulations.Two different types of waveforms,namely the unipol...In this study the effects of the actuation waveforms on the droplet generation in a drop-on-demand inkjet printing are studied systematically by numerical simulations.Two different types of waveforms,namely the unipolar and bipolar actuations,are investigated for three fluids with different physical properties.We focus on two key parameters,which are the dwell time and the velocity amplitude.For the unipolar driving,the ejection velocity and the ejected liquid volume are both increased as the velocity amplitude becomes larger.The dwell time only has minor effects on both the ejection velocity and the ejected liquid volume.The ejection velocity decreases significantly for large liquid viscosity,while the influences of viscosity on the ejected liquid volume are much weaker.Four different droplet morphologies and the corresponding parameter ranges are identified.The droplet radius can be successfully reduced to about 40%e of the nozzle exit radius.For the bipolar waveforms,same droplet morphologies are observed but with shifted boundaries in the phase space.The minimal radius of stable droplet produced by the bipolar waveforms is even smaller compared to the unipolar ones.展开更多
With the acceleration of the pace of social life and the emergence of the convenience economy,the requirements for on-demand cooking services have increased due to the increasing demand for food quality and the health...With the acceleration of the pace of social life and the emergence of the convenience economy,the requirements for on-demand cooking services have increased due to the increasing demand for food quality and the health concerns associated with takeaway food,as well as the lack of cooking skills.This paper aims to analyze the business model of on-demand cooking service platforms in China with the theory of Business Model Canvas proposed by Alexander Osterwalder.By exploring the advantages and disadvantages of the business model of on-demand door-to-door cooking,the study seeks to provide relevant recommendations.展开更多
基金supported by the Tsinghua University–Toyota Research Center Project。
文摘As an accurate 2D/3D fabrication tool,inkjet printing technology has great potential in preparation of micro electronic devices.The morphology of droplets produced by the inkjet printer has a great impact on the accuracy of deposition.In this study,the drop-on-demand(DoD)inkjet simulation model was established,and the accuracy of the simulation model was verified by corresponding experiments.The simulation result shows that the velocity of the droplet front and tail,as well as the time to disconnect from the nozzle is mainly affected by density(ρ),viscosity(μ)and surface tension(σ)of droplets.When the liquid filament is about to disconnect from the nozzle,the filament length and filament front velocity are found to have a linear correlation withσ/ρμand ln(ρ/(μσ1/2)).
基金Project supported by the National Natural Science Foundation of China(No.11802004)
文摘The droplet formation dynamics of a Newtonian liquid in a drop-on-demand (DOD) inkjet process is numerically investigated by using a volume-of-fluid (VOF) method. We focus on the nozzle geometry, wettability of the interior surface, and the fluid properties to achieve the stable droplet formation with higher velocity. It is found that a nozzle with contracting angle of 45° generates the most stable and fastest single droplet, which is beneficial for the enhanced printing quality and high-throughput printing rate. For this nozzle with the optimal geometry, we systematically change the wettability of the interior surface, i.e., different contact angles. As the contact angle increases, pinch-off time increases and the droplet speed reduces. Finally, fluids with different properties are investigated to identify the printability range.
基金The authors acknowledge the financial support from the NationalNatural Science Foundation ofChina(No.52275562)the Technology Innovation Fund of Huazhong University of Science and Technology(No.2022JYCXJJ015).
文摘On-demand droplet sorting is extensively applied for the efficient manipulation and genome-wide analysis of individual cells.However,state-of-the-art microfluidic chips for droplet sorting still suffer from low sorting speeds,sample loss,and labor-intensive preparation procedures.Here,we demonstrate the development of a novel microfluidic chip that integrates droplet generation,on-demand electrostatic droplet charging,and high-throughput sorting.The charging electrode is a copper wire buried above the nozzle of the microchannel,and the deflecting electrode is the phosphate buffered saline in the microchannel,which greatly simplifies the structure and fabrication process of the chip.Moreover,this chip is capable of high-frequency droplet generation and sorting,with a frequency of 11.757 kHz in the drop state.The chip completes the selective charging process via electrostatic induction during droplet generation.On-demand charged microdroplets can arbitrarilymove to specific exit channels in a three-dimensional(3D)-deflected electric field,which can be controlled according to user requirements,and the flux of droplet deflection is thereby significantly enhanced.Furthermore,a lossless modification strategy is presented to improve the accuracy of droplet deflection or harvest rate from 97.49% to 99.38% by monitoring the frequency of droplet generation in real time and feeding it back to the charging signal.This chip has great potential for quantitative processing and analysis of single cells for elucidating cell-to-cell variations.
基金supported by Project funded by China Postdoctoral Science Foundation(No.2021MD703980)。
文摘To improve the efficiency and fairness of the spectrum allocation for ground communication assisted by unmanned aerial vehicles(UAVs),a joint optimization method for on-demand deployment and spectrum allocation of UAVs is proposed,which is modeled as a mixed-integer non-convex optimization problem(MINCOP).An algorithm to estimate the minimum number of required UAVs is firstly proposed based on the pre-estimation and simulated annealing.The MINCOP is then decomposed into three sub-problems based on the block coordinate descent method,including the spectrum allocation of UAVs,the association between UAVs and ground users,and the deployment of UAVs.Specifically,the optimal spectrum allocation is derived based on the interference mitigation and channel reuse.The association between UAVs and ground users is optimized based on local iterated optimization.A particle-based optimization algorithm is proposed to resolve the subproblem of the UAVs deployment.Simulation results show that the proposed method could effectively improve the minimum transmission rate of UAVs as well as user fairness of spectrum allocation.
基金National Natural Science Foundation of China(Grants 91848201,11988102,11521202,11872004.11802004)The authors also acknowledge the partial support from the Beijing Natural Science Foundation(Grants L172002)+1 种基金A.B.Aqecl would like to thank the Chinese Scholarship Council(CSC)for providing Chinese Government Scholarship(CGs)The numericalsimulations were performed on the National Super Computing Centerin Tianjin.China.
文摘In this study the effects of the actuation waveforms on the droplet generation in a drop-on-demand inkjet printing are studied systematically by numerical simulations.Two different types of waveforms,namely the unipolar and bipolar actuations,are investigated for three fluids with different physical properties.We focus on two key parameters,which are the dwell time and the velocity amplitude.For the unipolar driving,the ejection velocity and the ejected liquid volume are both increased as the velocity amplitude becomes larger.The dwell time only has minor effects on both the ejection velocity and the ejected liquid volume.The ejection velocity decreases significantly for large liquid viscosity,while the influences of viscosity on the ejected liquid volume are much weaker.Four different droplet morphologies and the corresponding parameter ranges are identified.The droplet radius can be successfully reduced to about 40%e of the nozzle exit radius.For the bipolar waveforms,same droplet morphologies are observed but with shifted boundaries in the phase space.The minimal radius of stable droplet produced by the bipolar waveforms is even smaller compared to the unipolar ones.
文摘With the acceleration of the pace of social life and the emergence of the convenience economy,the requirements for on-demand cooking services have increased due to the increasing demand for food quality and the health concerns associated with takeaway food,as well as the lack of cooking skills.This paper aims to analyze the business model of on-demand cooking service platforms in China with the theory of Business Model Canvas proposed by Alexander Osterwalder.By exploring the advantages and disadvantages of the business model of on-demand door-to-door cooking,the study seeks to provide relevant recommendations.
