Nitrate synthesis is an important process for agriculture and industry,but suffers from energy-intensive steps including the synthesis and subsequent oxidation of ammonia.Herein,we present a selective N_(2)transformat...Nitrate synthesis is an important process for agriculture and industry,but suffers from energy-intensive steps including the synthesis and subsequent oxidation of ammonia.Herein,we present a selective N_(2)transformation to nitrate by guiding the charge neutralization of self-electrified water microdroplets in an artificial cloud generated with the portable ultrasonic atomizer.The electron and ion transfer in the charge neutralization of water microdroplets on metal micromesh enables an up to~40-fold increase in the reactivity of nitrate formation reaction driven by ultrasonic energy.A robust semi-continuous N_(2)oxidation by a Ni-mesh-screened cloud system was achieved,providing nitrate with~12 mM concentration every 20 h.These findings emphasize the potential of harnessing the microdroplet-mediated cloud electrochemistry of N_(2)in decentralizing the current mass production of fertilizer.展开更多
The mechanism of microdroplet coalescence is a fundamental issue for droplet-based microfluidics. We developed an asymmetric expansion (a rectangular groove) along one side of a microchannel to achieve multiple-microd...The mechanism of microdroplet coalescence is a fundamental issue for droplet-based microfluidics. We developed an asymmetric expansion (a rectangular groove) along one side of a microchannel to achieve multiple-microdroplet trapping, collision, and coalescence. Compared with reported symmetric expansions, this asymmetric groove could easily trap microdroplets and control two or three microdroplet coalescences precisely without a requirement for temporal and spatial synchronization. To reveal the mechanisms of multiple-droplet coalescences in a groove, we observed five different coalescence patterns under different flow conditions. Moreover, we characterized the flow behavior quantitatively by simulating the velocity vector fields in both the microdroplets and continuous phase, finding good agreement with experiments. Finally, a map of coalescence forms with different capillary numbers () and flow ratios () was obtained. The results could provide a useful guidance for the design and application of droplet-based microfluidic devices.展开更多
Biopolymers, including DNA and peptides have been used as excellent self-assembling building blocks for programmable single-component or hybrid materials, due to their controlled molecular interactions.However, combin...Biopolymers, including DNA and peptides have been used as excellent self-assembling building blocks for programmable single-component or hybrid materials, due to their controlled molecular interactions.However, combining two assembling principles of DNA-based programmability and peptide-based specific molecular interactions for hybrid structures to microscale has not yet been achieved. In this study,we describe a hybrid microsystem that emerges from the co-assembly of DNA origami structure and short elastin-like polypeptide conjugated oligonucleotides, and initiates liquid-liquid phase separation to generate microdroplets upon heating above the transition temperature. Moreover, the hybrid microdroplets are capable for vip molecule trapping and perform bi-/tri-enzymatic cascades with rate enhancements as open “microreactors”. Our programmed assembled DNA-peptide microsystem represents a new combination of DNA nanotechnology and peptide science and opens potential application routes toward lifeinspired biomaterials.展开更多
Study of stable liquid crystal(LC)microdroplets is of great significance for LC dynamics in con fined space or at topological surface.However,the fabrication of LC microdroplets with diverse shape without ionic gelati...Study of stable liquid crystal(LC)microdroplets is of great significance for LC dynamics in con fined space or at topological surface.However,the fabrication of LC microdroplets with diverse shape without ionic gelati on agents still remai ns challe nging due to the fluid instability.Here,we utilize the microfluidic tech no logy to prepare graphe ne oxide(GO)LC microdroplets with various morphologies based on the anomalous rheological property of GO aqueous dispersion.Different from LC of one-dimensional polymer,LC containing two-dimensional GO sheets exhibits considerable viscoelasticity and weak extensibility,resulting from the planar molecular conformation and the absence of intermolecular entangleme nts.The low exte risibility ensures that GO aqueous suspension is discretized into mono dispersed microdroplets rather than thin thread in the microfluidic channels.The large viscoelasticity and ultra-1 ong relaxation time of GO LC enable the diverse stable morphologies of microdroplets.The droplet morphology is well con trolled from sphere to teardrop by modulati ng the competition between GO viscoelasticity and in terfacial ten sion.The two-dimensional GO LC featuri ng unique rheological property provides a novel system for the microfluidic field,and corresponding topological stability enriches the LC dyn amics and ope ns a new pathway for desig ning graphe ne-based materials.展开更多
Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the s...Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.展开更多
Zirconium metal-organic frameworks(Zr-MOFs)represent the most promising candidates among MOFs for industrial utilizations owing to their high porosity and excellent stability.However,the efficient synthesis of Zr-MOFs...Zirconium metal-organic frameworks(Zr-MOFs)represent the most promising candidates among MOFs for industrial utilizations owing to their high porosity and excellent stability.However,the efficient synthesis of Zr-MOFs combining with continuous production,high productivity and good product quality still remains a critical issue for practical applications.Herein,we report an efficient method of synthesizing a series of Zr-MOFs through a microdroplet flow reaction,which is more accommodate the requirements of industrial production.Four types of Zr-based MOFs with different ligands and topologies(MOF-801,MOF-804,DUT-67 and MOF-808)were produced as a pure phase of high quality crystalline with uniform morphologies.Furthermore,this series of Zr-MOFs were obtained in a continuous way and at a space-time yield(STY)highly up to 367.2 kg m-3 d-1.These MOFs exhibit the similar pore structure and thermal stability with that prepared from conventional solvothermal synthesis.CO2 sorption studies on these MOFs demonstrate that the hydroxyl groups on ligand can render MOFs with high CO2/N2 selectivity.展开更多
ABSTRACT The Raman intensitics of gas molecules were found to be enormously enhanced in the presence of Hg-microdroplets.The enhancement factor for the molecules studied was found to be over 20.
In this paper, an electrohydrodynamic approach is used to model and study dynamics of evaporating microdroplets in digital microfluidic systems. A numerical eleetrohydrodynamic approach is used to calculate the drivin...In this paper, an electrohydrodynamic approach is used to model and study dynamics of evaporating microdroplets in digital microfluidic systems. A numerical eleetrohydrodynamic approach is used to calculate the driving force and shear force （due to the walls）. Effects of contact line pinning is considered by adding a three-phase contact line force, and also considering dynamic contact angle which modifies the mierodroplet boundary conditions. Since air is used as the filler fluid, the drag force is neglected. Although energy equation is not solved （constant temperature assumption）, effects of the evaporation is considered from two aspects： It is shown that an additional force is needed to balance the dynamic equation of the mierodroplet motion. Also, at each time step the microdroplet interface has to be deformed due to the change in the microdroplet radius. Important findings of the proposed model includes the transient velocity and displacement of the microdroplet as well as the driving and opposing forces acting on the microdroplet as functions of time. It is shown that mass loss due to evaporation tends to accelerate the droplet; whereas the competitive effect of the reduced driving force decelerates the droplet at the end of motion. The modeling results indicate that evaporation plays a crucial role in microdroplet motion by changing the force balance and the microdroplet boundary condition.展开更多
Given recent interest in laboratory automation and miniaturization,the microdroplet research space has expanded across research disciplines and sectors.In turn,the microdroplet field is continually evolving and seekin...Given recent interest in laboratory automation and miniaturization,the microdroplet research space has expanded across research disciplines and sectors.In turn,the microdroplet field is continually evolving and seeking new methods to generate microdroplets,especially in ways that can be integrated into diverse(microfluidic)workflows.Herein,we present a convenient,low-cost,and re-usable microdroplet generation device,termed as the“NanoWand,”which enables microdroplet formation in the nanoliter volume range through modulated surface energy and roughness,that is,an open surface energy trap(oSET),using commercially available and readily assembled coating and substrate materials.A wand-like shape is excised from a microscope glass cover slip via laser-micromachining and rendered hydrophobic;a circle is then cut-out from the hydrophobically modified wand’s tip using laser-micromachining to create the oSET.By adjusting the size of the oSET with laser-micromachining,the volume of the microdroplet can be similarly controlled.Using liquid microjunction-surface sampling probe-mass spectrometry(LMJ-SSPMS),specific NanoWand droplet capture volumeswere estimated to be 117±23.6 nL,198±30.3 nL,and 277±37.1 nL,corresponding to oSET diameters of 0.75,1.00,and 1.25 mm,respectively.This simple approach provides a user-friendly way to form and transfer microdroplets that could be integrated into different liquid handling applications,especially when combined with the LMJ-SSP and ambient ionization MS as a powerful and rapid analytical tool.展开更多
Theadvancementofdigital microfluidics technology has been pivotal in academic research andengineering applications.However,the prevailing limitation is that traditional voltage sources generate an excess of Joule heat...Theadvancementofdigital microfluidics technology has been pivotal in academic research andengineering applications.However,the prevailing limitation is that traditional voltage sources generate an excess of Joule heat,adversely impacting droplet operation.Moreover,the power supply equipment required by digital microfluidics limits its applications.Here,we propose a self-powered microdroplet manipulation(SMDM)via triboelectric nanogenerator(TENG),which presents a capability for spliting and mixing different kinds of droplets.Fundamentally,SMDM is based on the electroosmotic flow principle,thereby enabling droplet spliting in the range of from 2 to 630μL.Notably,for droplet spliting in the range of from 5 to 60μL,the TENG only requires a power output ranging from 2.704 to 6.084 mW.In addition,SMDM demonstrates proficiency in droplet mixing,which achieves complete mixing of 10μL droplets in 60 s and 30μL droplets in a mere 53 s.Therefore,leveraging the strengths of the TENG,a self-powered microdroplet manipulated system is designed for digital microfluidics.It carries significant advantages over the traditional voltage source,including self-powered,low-Joule heat,increased safety and enhanced portability.This research provides a new solution for portable applications of digital microfluidics.展开更多
The separation of the isotopologues of water is critically important for purification and practical applications;however,effective separation methods for this purpose are currently lacking.The similar physical and che...The separation of the isotopologues of water is critically important for purification and practical applications;however,effective separation methods for this purpose are currently lacking.The similar physical and chemical properties of deuterium oxide(D_(2)O)and water(H_(2)O)cause challenges to existing techniques,which are both complex and energy-intensive,especially for large-scale separation of D_(2)O from H_(2)O/D_(2)O mixtures.Herein,we discovered that D_(2)O can be removed from H_(2)O/D_(2)O mixture through a three-phase interface in sessile microdroplets.This process converts D_(2)O/H_(2)O mixed microdroplets,ranging from 0.5 to 1.5μL with D_(2)O concentrations from 3%to 90%,into natural water within 5 to 20 min.Theoretical simulations,including the evaporation and H-D exchange on various substrates,indicate that the removal is attributed to the H-D exchange.This result is reinforced by the experimental results,where platinum,a known catalyst for H-D exchange,can exceptionally enhance the separation of H_(2)O/D_(2)O.The microdroplet-based removal of D_(2)O occurs efficiently under ambient conditions,offering a costeffective approach for separating water isotopologues.展开更多
Droplets are ubiquitous in nature and play an essential role in spray cooling,which is a highly efficient cooling approach for high-power-density miniaturized electronic devices.However,conventional pressure-driven sp...Droplets are ubiquitous in nature and play an essential role in spray cooling,which is a highly efficient cooling approach for high-power-density miniaturized electronic devices.However,conventional pressure-driven spray faces significant challenges in controlling microdroplet characteristics,particularly the droplet size and spray direction,both of which critically impact cooling performance.Herein,to conquer these challenges,we designed an acoustic microdroplet atomizer composed of a lead zirconate titanate(PZT)transducer and silicon inverted pyramid nozzles.This design enables precise control of droplet generation,overcoming the limitations of traditional spray methods.The acoustic atomization technology minimizes excess liquid accumulation while significantly enhancing thin liquid film evaporation.Compared to the conventional droplet generation techniques such as pressure-driven,injector-based,and piezoelectric spray,our acoustic atomizer achieves superior cooling performance.Notably,we demonstrate a high heat flux of∼220W/cm2 with a 3.6-fold enhancement at a low flow rate of 24 mL/min,achieving significantly improved cooling efficiency.Finally,our acoustic atomizer provides precise control over droplet size,velocity,and flow rate by adjusting the number of nozzles and the PZT transducer’s resonant frequency,elevating spray cooling performance.This novel acoustic atomization cooling technology holds great promise for practical applications,particularly in the thermal management of compact electronic components.展开更多
By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which canno...By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state. The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCl), 75.7% and 93.3% (NaCl), and 69.9% and 96.6% (NH4Cl), respectively. In addition, it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.展开更多
In this Letter,a dye-doped cholesteric liquid crystal(DDCLC)-filled hollow glass microsphere is demonstrated to be a resonator with good temperature response.A diglycerol layer is used to wrap the DDCLCs microdroplet ...In this Letter,a dye-doped cholesteric liquid crystal(DDCLC)-filled hollow glass microsphere is demonstrated to be a resonator with good temperature response.A diglycerol layer is used to wrap the DDCLCs microdroplet to keep it steady and control its orientation.The whispering gallery mode(WGM)lasing and photonic band gap(PBG)lasing caused by two different mechanisms were obtained under the pump of a pulsed laser,and the temperature response of these two kinds of lasing was studied.For the liquid crystal and chiral material used in this Letter,both the WGM lasing and the PBG lasing have a blue shift in wavelength with increasing temperature.展开更多
At present,study on dynamic tensile properties and atomic chain fabrication of single nanowire,for understanding its dynamic tensile properties and unique physical properties of atomic chain to fabricate atom scale de...At present,study on dynamic tensile properties and atomic chain fabrication of single nanowire,for understanding its dynamic tensile properties and unique physical properties of atomic chain to fabricate atom scale devices,is one of frontier research issues in nanoscale science.However,how to assemble single nanowire on a tensible microstructure becomes one of the most difficult problems,which severely restricts the development of this research field.In this paper,after the ultrahigh tensible microelectrode chip is fabricated by MEMS technology,hexamethyldisilazane is utilized to improve hydrophobicity of the chip,and then a microdroplet dielectrophoresis experimental platform and technology is developed to assemble single nanowire on the sensible microelectrode.Experimental results show that accurate and efficient assembly of single Cu nanowire is realized,which contribute greatly to the further research of dynamic tensile properties and atomic chain fabrication.And for guiding the assembly experiments,finite element technology is also utilized to analyze the local microelectro field around the microelectrodes during dieletrophoresis experiments.展开更多
The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be mo...The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be more complex,necessitating new theoretical frameworks,though key empirical evidence remains elusive.In this study,we used microdroplets to investigate the crystallization of sodium halides(NaCl,NaBr,and NaI)under homogeneous nucleation conditions across a wide range of supersaturations.In the evaporating droplet,NaCl follows the classical nucleation pathway,whereas NaBr and NaI exhibit the formation of an intermediate phase prior to the nucleation of anhydrous and hydrous single crystals,respectively.Optical and computational analyses indicate that these intermediate phases are liquid crystal phases composed of contact ion pairs.These findings establish a new theoretical framework for crystal nucleation and growth and offer methods to control nucleation pathways,enabling us to achieve desired crystals regardless of specific conditions.展开更多
基金supported by the National Key R&D Program of China(2022YFA1504603)the National Natural Science Foundation of China(22025206,22172163)+1 种基金the Dalian Innovation Support Plan for High Level Talents(2022RG13)the Fundamental Research Funds for the Central Universities(20720220008)。
文摘Nitrate synthesis is an important process for agriculture and industry,but suffers from energy-intensive steps including the synthesis and subsequent oxidation of ammonia.Herein,we present a selective N_(2)transformation to nitrate by guiding the charge neutralization of self-electrified water microdroplets in an artificial cloud generated with the portable ultrasonic atomizer.The electron and ion transfer in the charge neutralization of water microdroplets on metal micromesh enables an up to~40-fold increase in the reactivity of nitrate formation reaction driven by ultrasonic energy.A robust semi-continuous N_(2)oxidation by a Ni-mesh-screened cloud system was achieved,providing nitrate with~12 mM concentration every 20 h.These findings emphasize the potential of harnessing the microdroplet-mediated cloud electrochemistry of N_(2)in decentralizing the current mass production of fertilizer.
基金supported by the Beijing Municipal Natural Science Foundation (Grant 7152012)the General Program of Science and Technology Development Project of the Beijing Municipal Education Commission (Grant KM201610005002)+2 种基金the National Natural Science Foundation of China (Grant 11572013)the China Scholarship Council (Grant 201406545031)the Training Plan of New Talent of Beijing University of Technology (Grant 2015-RX-L02)
文摘The mechanism of microdroplet coalescence is a fundamental issue for droplet-based microfluidics. We developed an asymmetric expansion (a rectangular groove) along one side of a microchannel to achieve multiple-microdroplet trapping, collision, and coalescence. Compared with reported symmetric expansions, this asymmetric groove could easily trap microdroplets and control two or three microdroplet coalescences precisely without a requirement for temporal and spatial synchronization. To reveal the mechanisms of multiple-droplet coalescences in a groove, we observed five different coalescence patterns under different flow conditions. Moreover, we characterized the flow behavior quantitatively by simulating the velocity vector fields in both the microdroplets and continuous phase, finding good agreement with experiments. Finally, a map of coalescence forms with different capillary numbers () and flow ratios () was obtained. The results could provide a useful guidance for the design and application of droplet-based microfluidic devices.
基金supported by the National Natural Science Foundation of China (No. 31600802)。
文摘Biopolymers, including DNA and peptides have been used as excellent self-assembling building blocks for programmable single-component or hybrid materials, due to their controlled molecular interactions.However, combining two assembling principles of DNA-based programmability and peptide-based specific molecular interactions for hybrid structures to microscale has not yet been achieved. In this study,we describe a hybrid microsystem that emerges from the co-assembly of DNA origami structure and short elastin-like polypeptide conjugated oligonucleotides, and initiates liquid-liquid phase separation to generate microdroplets upon heating above the transition temperature. Moreover, the hybrid microdroplets are capable for vip molecule trapping and perform bi-/tri-enzymatic cascades with rate enhancements as open “microreactors”. Our programmed assembled DNA-peptide microsystem represents a new combination of DNA nanotechnology and peptide science and opens potential application routes toward lifeinspired biomaterials.
基金by the National Natural Science Foundation of China(Nos.52090030,51533008,51703194,51973191,51873191 and 51803177)National Key R&D Program of China(No.2016YFA0200200),Hundred Talents Program of Zhejiang University(No.188020*194231701/113),Key Research and Development Plan of Zhejiang Province(2018C01049)+1 种基金the Fundamental Research Funds for the Central Universities(No.K20200060)Key Laboratory of Novel Adsorpti on and Separati on Materials and Applicatio n Technology of Zhejiang Province(No.512301-121502).
文摘Study of stable liquid crystal(LC)microdroplets is of great significance for LC dynamics in con fined space or at topological surface.However,the fabrication of LC microdroplets with diverse shape without ionic gelati on agents still remai ns challe nging due to the fluid instability.Here,we utilize the microfluidic tech no logy to prepare graphe ne oxide(GO)LC microdroplets with various morphologies based on the anomalous rheological property of GO aqueous dispersion.Different from LC of one-dimensional polymer,LC containing two-dimensional GO sheets exhibits considerable viscoelasticity and weak extensibility,resulting from the planar molecular conformation and the absence of intermolecular entangleme nts.The low exte risibility ensures that GO aqueous suspension is discretized into mono dispersed microdroplets rather than thin thread in the microfluidic channels.The large viscoelasticity and ultra-1 ong relaxation time of GO LC enable the diverse stable morphologies of microdroplets.The droplet morphology is well con trolled from sphere to teardrop by modulati ng the competition between GO viscoelasticity and in terfacial ten sion.The two-dimensional GO LC featuri ng unique rheological property provides a novel system for the microfluidic field,and corresponding topological stability enriches the LC dyn amics and ope ns a new pathway for desig ning graphe ne-based materials.
基金supported by National Natural Science Foundation of China(21725601)。
文摘Microdroplets and their dispersion,with a large specific surface area and a short diffusion distance,have been applied in various unit operations and reaction processes.However,it is still a challenge to control the size and size distribution of microdroplets,especially for high-throughput generation.In this work,a novel ultra-high speed rotating packed bed(UHS-RPB)was invented,in which rotating foam packing with a speed of 4000-12000 r·min^(-1) provides microfluidic channels to disperse liquid into microdroplets with high throughput.Then generated microdroplets can be directly dispersed into a continuous falling film for obtaining a mixture of microdroplet dispersion.In this UHS-RPB,the effects of rotational speed,liquid initial velocity,liquid viscosity,liquid surface tension and packing pore size on the average size(d_(32))and size distribution of microdroplets were systematically investigated.Results showed that the UHS-RPB could produce microdroplets with a d_(32) of 25-63μm at a liquid flow rate of 1025 L·h^(-1),and the size distribution of the microdroplets accords well with Rosin-Rammler distribution model.In addi-tion,a correlation was established for the prediction of d_(32),and the predicted d_(32) was in good agreement with the experimental data with a deviation within±15%.These results demonstrated that UHS-RPB could be a promising candidate for controllable preparation of uniform microdroplets.
基金supported by grants from the National Natural Science Foundation of China(Nos.21401215,21473254)the Special Project Fund of"Taishan Scholars"of Shandong Province(No.ts201511017)
文摘Zirconium metal-organic frameworks(Zr-MOFs)represent the most promising candidates among MOFs for industrial utilizations owing to their high porosity and excellent stability.However,the efficient synthesis of Zr-MOFs combining with continuous production,high productivity and good product quality still remains a critical issue for practical applications.Herein,we report an efficient method of synthesizing a series of Zr-MOFs through a microdroplet flow reaction,which is more accommodate the requirements of industrial production.Four types of Zr-based MOFs with different ligands and topologies(MOF-801,MOF-804,DUT-67 and MOF-808)were produced as a pure phase of high quality crystalline with uniform morphologies.Furthermore,this series of Zr-MOFs were obtained in a continuous way and at a space-time yield(STY)highly up to 367.2 kg m-3 d-1.These MOFs exhibit the similar pore structure and thermal stability with that prepared from conventional solvothermal synthesis.CO2 sorption studies on these MOFs demonstrate that the hydroxyl groups on ligand can render MOFs with high CO2/N2 selectivity.
文摘ABSTRACT The Raman intensitics of gas molecules were found to be enormously enhanced in the presence of Hg-microdroplets.The enhancement factor for the molecules studied was found to be over 20.
文摘In this paper, an electrohydrodynamic approach is used to model and study dynamics of evaporating microdroplets in digital microfluidic systems. A numerical eleetrohydrodynamic approach is used to calculate the driving force and shear force （due to the walls）. Effects of contact line pinning is considered by adding a three-phase contact line force, and also considering dynamic contact angle which modifies the mierodroplet boundary conditions. Since air is used as the filler fluid, the drag force is neglected. Although energy equation is not solved （constant temperature assumption）, effects of the evaporation is considered from two aspects： It is shown that an additional force is needed to balance the dynamic equation of the mierodroplet motion. Also, at each time step the microdroplet interface has to be deformed due to the change in the microdroplet radius. Important findings of the proposed model includes the transient velocity and displacement of the microdroplet as well as the driving and opposing forces acting on the microdroplet as functions of time. It is shown that mass loss due to evaporation tends to accelerate the droplet; whereas the competitive effect of the reduced driving force decelerates the droplet at the end of motion. The modeling results indicate that evaporation plays a crucial role in microdroplet motion by changing the force balance and the microdroplet boundary condition.
基金Natural Sciences and Engineering Research Council(NSERC),Grant/Award Number:RGPIN-2022-03833CMC Microsystems,Grant/Award Numbers:10268,10731。
文摘Given recent interest in laboratory automation and miniaturization,the microdroplet research space has expanded across research disciplines and sectors.In turn,the microdroplet field is continually evolving and seeking new methods to generate microdroplets,especially in ways that can be integrated into diverse(microfluidic)workflows.Herein,we present a convenient,low-cost,and re-usable microdroplet generation device,termed as the“NanoWand,”which enables microdroplet formation in the nanoliter volume range through modulated surface energy and roughness,that is,an open surface energy trap(oSET),using commercially available and readily assembled coating and substrate materials.A wand-like shape is excised from a microscope glass cover slip via laser-micromachining and rendered hydrophobic;a circle is then cut-out from the hydrophobically modified wand’s tip using laser-micromachining to create the oSET.By adjusting the size of the oSET with laser-micromachining,the volume of the microdroplet can be similarly controlled.Using liquid microjunction-surface sampling probe-mass spectrometry(LMJ-SSPMS),specific NanoWand droplet capture volumeswere estimated to be 117±23.6 nL,198±30.3 nL,and 277±37.1 nL,corresponding to oSET diameters of 0.75,1.00,and 1.25 mm,respectively.This simple approach provides a user-friendly way to form and transfer microdroplets that could be integrated into different liquid handling applications,especially when combined with the LMJ-SSP and ambient ionization MS as a powerful and rapid analytical tool.
基金The authors are grateful for the support from the National Natural Science Foundation of China(No.52405052)the Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(No.GZKF-202305)+1 种基金the Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(No.GZB20230731)the National Key R&D Project from Minister of Science and Technology(No.2021YFA1201601).
文摘Theadvancementofdigital microfluidics technology has been pivotal in academic research andengineering applications.However,the prevailing limitation is that traditional voltage sources generate an excess of Joule heat,adversely impacting droplet operation.Moreover,the power supply equipment required by digital microfluidics limits its applications.Here,we propose a self-powered microdroplet manipulation(SMDM)via triboelectric nanogenerator(TENG),which presents a capability for spliting and mixing different kinds of droplets.Fundamentally,SMDM is based on the electroosmotic flow principle,thereby enabling droplet spliting in the range of from 2 to 630μL.Notably,for droplet spliting in the range of from 5 to 60μL,the TENG only requires a power output ranging from 2.704 to 6.084 mW.In addition,SMDM demonstrates proficiency in droplet mixing,which achieves complete mixing of 10μL droplets in 60 s and 30μL droplets in a mere 53 s.Therefore,leveraging the strengths of the TENG,a self-powered microdroplet manipulated system is designed for digital microfluidics.It carries significant advantages over the traditional voltage source,including self-powered,low-Joule heat,increased safety and enhanced portability.This research provides a new solution for portable applications of digital microfluidics.
基金supported by the National Key Research and Development Program of China(2022YFA1503104)the National Natural Science Foundation of China(22479088,22403057,22002070)+2 种基金the Natural Science Foundation of Shandong Province(ZR2023QB204)the financial support from the Program of Young Scholars Future Program of Shandong Universitythe financial support from the Program of Taishan Scholars Project(tspd20230601)。
文摘The separation of the isotopologues of water is critically important for purification and practical applications;however,effective separation methods for this purpose are currently lacking.The similar physical and chemical properties of deuterium oxide(D_(2)O)and water(H_(2)O)cause challenges to existing techniques,which are both complex and energy-intensive,especially for large-scale separation of D_(2)O from H_(2)O/D_(2)O mixtures.Herein,we discovered that D_(2)O can be removed from H_(2)O/D_(2)O mixture through a three-phase interface in sessile microdroplets.This process converts D_(2)O/H_(2)O mixed microdroplets,ranging from 0.5 to 1.5μL with D_(2)O concentrations from 3%to 90%,into natural water within 5 to 20 min.Theoretical simulations,including the evaporation and H-D exchange on various substrates,indicate that the removal is attributed to the H-D exchange.This result is reinforced by the experimental results,where platinum,a known catalyst for H-D exchange,can exceptionally enhance the separation of H_(2)O/D_(2)O.The microdroplet-based removal of D_(2)O occurs efficiently under ambient conditions,offering a costeffective approach for separating water isotopologues.
基金National Natural Science Foundation of China,Grant/Award Number:52476060。
文摘Droplets are ubiquitous in nature and play an essential role in spray cooling,which is a highly efficient cooling approach for high-power-density miniaturized electronic devices.However,conventional pressure-driven spray faces significant challenges in controlling microdroplet characteristics,particularly the droplet size and spray direction,both of which critically impact cooling performance.Herein,to conquer these challenges,we designed an acoustic microdroplet atomizer composed of a lead zirconate titanate(PZT)transducer and silicon inverted pyramid nozzles.This design enables precise control of droplet generation,overcoming the limitations of traditional spray methods.The acoustic atomization technology minimizes excess liquid accumulation while significantly enhancing thin liquid film evaporation.Compared to the conventional droplet generation techniques such as pressure-driven,injector-based,and piezoelectric spray,our acoustic atomizer achieves superior cooling performance.Notably,we demonstrate a high heat flux of∼220W/cm2 with a 3.6-fold enhancement at a low flow rate of 24 mL/min,achieving significantly improved cooling efficiency.Finally,our acoustic atomizer provides precise control over droplet size,velocity,and flow rate by adjusting the number of nozzles and the PZT transducer’s resonant frequency,elevating spray cooling performance.This novel acoustic atomization cooling technology holds great promise for practical applications,particularly in the thermal management of compact electronic components.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20673010 and 20605004)Fundamental Research Foundation of BIT (Grant No. 20060742003)+1 种基金Program of Introducing Talents of Discipline to Universities (Grant No. B07012)China Postdoctoral Science Foundation (Grant No. 20070410467)
文摘By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state. The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCl), 75.7% and 93.3% (NaCl), and 69.9% and 96.6% (NH4Cl), respectively. In addition, it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.
基金This work was supported by the National Natural Science Foundation of China(Nos.U1531102,11603008,and 61107059)the Fundamental Research Funds for the Central Universities(No.HEUCF181116).
文摘In this Letter,a dye-doped cholesteric liquid crystal(DDCLC)-filled hollow glass microsphere is demonstrated to be a resonator with good temperature response.A diglycerol layer is used to wrap the DDCLCs microdroplet to keep it steady and control its orientation.The whispering gallery mode(WGM)lasing and photonic band gap(PBG)lasing caused by two different mechanisms were obtained under the pump of a pulsed laser,and the temperature response of these two kinds of lasing was studied.For the liquid crystal and chiral material used in this Letter,both the WGM lasing and the PBG lasing have a blue shift in wavelength with increasing temperature.
基金supported by the National Natural Science Foundation of China(51375477 and 61375091)the CAS FEA International Partnership Program for Creative Research Teams
文摘At present,study on dynamic tensile properties and atomic chain fabrication of single nanowire,for understanding its dynamic tensile properties and unique physical properties of atomic chain to fabricate atom scale devices,is one of frontier research issues in nanoscale science.However,how to assemble single nanowire on a tensible microstructure becomes one of the most difficult problems,which severely restricts the development of this research field.In this paper,after the ultrahigh tensible microelectrode chip is fabricated by MEMS technology,hexamethyldisilazane is utilized to improve hydrophobicity of the chip,and then a microdroplet dielectrophoresis experimental platform and technology is developed to assemble single nanowire on the sensible microelectrode.Experimental results show that accurate and efficient assembly of single Cu nanowire is realized,which contribute greatly to the further research of dynamic tensile properties and atomic chain fabrication.And for guiding the assembly experiments,finite element technology is also utilized to analyze the local microelectro field around the microelectrodes during dieletrophoresis experiments.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2021R1C1C2006535)supported by the Korea Basic Science Institute(National Research Facilities and Equipment Center)grant funded by the Korea government(MSIT)(No.RS-2024-00403164)supported by the National Research Foundation of Korea grant funded by the Korea government,Ministry of Science and ICT(Development of Nanofiber Yarn Based Compound Sensor as a Comprehensive Wearable Healthcare Solution)(Grant No.RS-2024-00357296).
文摘The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be more complex,necessitating new theoretical frameworks,though key empirical evidence remains elusive.In this study,we used microdroplets to investigate the crystallization of sodium halides(NaCl,NaBr,and NaI)under homogeneous nucleation conditions across a wide range of supersaturations.In the evaporating droplet,NaCl follows the classical nucleation pathway,whereas NaBr and NaI exhibit the formation of an intermediate phase prior to the nucleation of anhydrous and hydrous single crystals,respectively.Optical and computational analyses indicate that these intermediate phases are liquid crystal phases composed of contact ion pairs.These findings establish a new theoretical framework for crystal nucleation and growth and offer methods to control nucleation pathways,enabling us to achieve desired crystals regardless of specific conditions.
