This review article presents an overview on the application of electrohydrodynamics and Joule heating effects in microfluidic chips.A brief introduction of microfluidic chips and a classification of electrohydrodynami...This review article presents an overview on the application of electrohydrodynamics and Joule heating effects in microfluidic chips.A brief introduction of microfluidic chips and a classification of electrohydrodynamics as well as the applications in microfluidic devices are first given.Then basic theories and governing equations of classical electromagnetics are summarized and electroviscous effects in pressure driven flows in a microchannel are presented.Principles and applications of DC electrokinetics,including DC electroosmotic flow,DC electrophoresis,as well as principles of AC electrokinetics,including AC electroosmotic flow and dielectrophoresis are also reviewed.Finally,Joule heating effects in both DC and AC electrokinetics,especially the newly discovered electrothermal flow,are summaried.展开更多
This paper presents a numerical analysis of Joule heating effect of electroosmo- sis in a finite-length microchannel made of the glass and polydimethylsiloxane （PDMS） polymer. The Poisson-Boltzmann equation of elect...This paper presents a numerical analysis of Joule heating effect of electroosmo- sis in a finite-length microchannel made of the glass and polydimethylsiloxane （PDMS） polymer. The Poisson-Boltzmann equation of electric double layer, the Navier-Stokes equation of liquid flow, and the liquid-solid coupled heat transfer equation are solved to investigate temperature behaviors of electroosmosis in a two-dimensional microchannel. The feedback effect of temperature variation on liquid properties （dielectric constant, vis- cosity, and thermal and electric conductivities） is taken into account. Numerical results indicate that there exists a heat developing length near the channel inlet where the flow velocity, temperature, pressure, and electric field rapidly vary and then approach to a steady state after the heat developing length, which may occupy a considerable portion of the microchannel in cases of thick chip and high electric field. The liquid temperature of steady state increases with the increase of the applied electric field, channel width, and chip thickness. The temperature on a PDMS wall is higher than that on a glass wall due to the difference of heat conductivities of materials. Temperature variations are found in the both longitudinal and transverse directions of the microchannel. The increase of the temperature on the wall decreases the charge density of the electric double layer. The longitudinal temperature variation induces a pressure gradient and changes the behavior of the electric field in the microchannel. The inflow liquid temperature does not change the liquid temperature of steady state and the heat developing length.展开更多
多晶硅电阻由于其独特的温度特性及电迁移效应,阻值受温度和电流的影响很大,针对应用于超高压BCD工艺中的多晶硅电阻,其可靠性需进行特别分析和设计。通过对0.18μm 700 V BCD工艺中不同掺杂浓度多晶硅电阻的测试与分析,结合多晶硅结构...多晶硅电阻由于其独特的温度特性及电迁移效应,阻值受温度和电流的影响很大,针对应用于超高压BCD工艺中的多晶硅电阻,其可靠性需进行特别分析和设计。通过对0.18μm 700 V BCD工艺中不同掺杂浓度多晶硅电阻的测试与分析,结合多晶硅结构、导电机制、焦耳热效应及电迁移理论,分析了焦耳热和电迁移对多晶硅电阻的影响,并实现了高压BCD工艺中高可靠性的多晶硅电阻。展开更多
What effect does electric current do on dislocation evolution of metals keeps being a confusing question to be answered and proved. To this end, the dislocation evolution of a superalloy with electric current was dire...What effect does electric current do on dislocation evolution of metals keeps being a confusing question to be answered and proved. To this end, the dislocation evolution of a superalloy with electric current was directly observed by electrical in-situ transmission electron microscopy in this work. Dislocations annihilation at first and then regeneration was found for the first time, which directly proves the existence of electron force during the electrically-assisted manufacturing. Dislocations regeneration would be driven by the electron force and the resistance softening by the local Joule heating effect. Resultantly,a base could be provided for future electrically-assisted research.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.50536010)the Shanghai Municipal Science&Technology Committee through Key Fundamental(Grant No.08JC1411100)
文摘This review article presents an overview on the application of electrohydrodynamics and Joule heating effects in microfluidic chips.A brief introduction of microfluidic chips and a classification of electrohydrodynamics as well as the applications in microfluidic devices are first given.Then basic theories and governing equations of classical electromagnetics are summarized and electroviscous effects in pressure driven flows in a microchannel are presented.Principles and applications of DC electrokinetics,including DC electroosmotic flow,DC electrophoresis,as well as principles of AC electrokinetics,including AC electroosmotic flow and dielectrophoresis are also reviewed.Finally,Joule heating effects in both DC and AC electrokinetics,especially the newly discovered electrothermal flow,are summaried.
基金supported by the National Natural Science Foundation of China (Nos.10872076 and 50805059)
文摘This paper presents a numerical analysis of Joule heating effect of electroosmo- sis in a finite-length microchannel made of the glass and polydimethylsiloxane （PDMS） polymer. The Poisson-Boltzmann equation of electric double layer, the Navier-Stokes equation of liquid flow, and the liquid-solid coupled heat transfer equation are solved to investigate temperature behaviors of electroosmosis in a two-dimensional microchannel. The feedback effect of temperature variation on liquid properties （dielectric constant, vis- cosity, and thermal and electric conductivities） is taken into account. Numerical results indicate that there exists a heat developing length near the channel inlet where the flow velocity, temperature, pressure, and electric field rapidly vary and then approach to a steady state after the heat developing length, which may occupy a considerable portion of the microchannel in cases of thick chip and high electric field. The liquid temperature of steady state increases with the increase of the applied electric field, channel width, and chip thickness. The temperature on a PDMS wall is higher than that on a glass wall due to the difference of heat conductivities of materials. Temperature variations are found in the both longitudinal and transverse directions of the microchannel. The increase of the temperature on the wall decreases the charge density of the electric double layer. The longitudinal temperature variation induces a pressure gradient and changes the behavior of the electric field in the microchannel. The inflow liquid temperature does not change the liquid temperature of steady state and the heat developing length.
文摘多晶硅电阻由于其独特的温度特性及电迁移效应,阻值受温度和电流的影响很大,针对应用于超高压BCD工艺中的多晶硅电阻,其可靠性需进行特别分析和设计。通过对0.18μm 700 V BCD工艺中不同掺杂浓度多晶硅电阻的测试与分析,结合多晶硅结构、导电机制、焦耳热效应及电迁移理论,分析了焦耳热和电迁移对多晶硅电阻的影响,并实现了高压BCD工艺中高可靠性的多晶硅电阻。
基金financially supported by the National Natural Science Foundation of China(Nos.U1737212 and U1637102)the Natural Science Foundation for Distinguished Young Scholars of Shaanxi Province(No.2019JC-09)。
文摘What effect does electric current do on dislocation evolution of metals keeps being a confusing question to be answered and proved. To this end, the dislocation evolution of a superalloy with electric current was directly observed by electrical in-situ transmission electron microscopy in this work. Dislocations annihilation at first and then regeneration was found for the first time, which directly proves the existence of electron force during the electrically-assisted manufacturing. Dislocations regeneration would be driven by the electron force and the resistance softening by the local Joule heating effect. Resultantly,a base could be provided for future electrically-assisted research.
