A dielectric analysis model for the fouling layer on the polyethersulfone composite ultrafiltration （UF） membrane and solution system, which consists of the solution, concentration polarization layer （CPL）, and ca...A dielectric analysis model for the fouling layer on the polyethersulfone composite ultrafiltration （UF） membrane and solution system, which consists of the solution, concentration polarization layer （CPL）, and cake layer, was established by virtue of the interfacial polarization and the electrostatic field theory. The effect of some important parameters, such as the depth, conductivity of CPL, and cake layer, on the dielectric spectroscopy （or dielectric relaxation properties） of the UF system was discussed by the parameter sensitivity analysis and the dielectric measurement. The simulations indicate that the CPL can be created rapidly and the cake layer formation is the dynamic balance process of growth and erosion in the process of UF. The key factor affecting on the dielectric spectrum of UF system is the electrical properties of the CPL and the cake layer. In comparison to the results of dielectric measurement, the simulations indicate that the model proposed in this work is valid and reliable to some degree for describing and explaining the dielectric relaxation phenomenon in UF system. It is very important to further understand the fouling behavior of membrane surface and optimize the controlling techniques of membrane fouling in the process of UF.展开更多
Digital microfluidics （DMF） is a versatile microfluidics technology that has significant application potential in the areas of automation and miniaturization. In DME discrete droplets containing samples and reagents...Digital microfluidics （DMF） is a versatile microfluidics technology that has significant application potential in the areas of automation and miniaturization. In DME discrete droplets containing samples and reagents are controlled to implement a series of operations via electrowetting-on-dielectric. This process works by apply- ing electrical potentials to an array of electrodes coated with a hydrophobic dielectric layer. Unlike microchannels, DMF facilitates precise control over multiple reaction processes without using complex pump, microvalve, and tubing networks. DMF also presents other distinct features, such as portability, less sample consumption, shorter chemical reaction time, flexibility, and easier combination with other technology types. Due to its unique advantages, DMF has been applied to a broad range of fields （e.g., chemistry, biology, medicine, and environment）. This study reviews the basic principles of droplet actuation, configuration design, and fabrication of the DMF device, as well as discusses the latest progress in DMF from the biochemistry perspective.展开更多
Using poly(amic acid)(PAA)as a precursor followed by thermal imidization,the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process.The influence of processi...Using poly(amic acid)(PAA)as a precursor followed by thermal imidization,the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process.The influence of processing factors,such as particle size,distribution mode and polymerization method on dielectric prop-erties was studied.Results revealed that the dielectric constant(ε)of the composite film increased by using bigger fillers or employing in situ polymerization and bimodal distribution.When the composite film contain-ing 50 Vol-%of BaTiO3 with size in 100 nm was pre-pared via in situ process,its dielectric constant reached 45 at 10 kHz.展开更多
基金This work was supported by the Natural Science Foundation of Shandong Province of China （No.Q2007B01）.
文摘A dielectric analysis model for the fouling layer on the polyethersulfone composite ultrafiltration （UF） membrane and solution system, which consists of the solution, concentration polarization layer （CPL）, and cake layer, was established by virtue of the interfacial polarization and the electrostatic field theory. The effect of some important parameters, such as the depth, conductivity of CPL, and cake layer, on the dielectric spectroscopy （or dielectric relaxation properties） of the UF system was discussed by the parameter sensitivity analysis and the dielectric measurement. The simulations indicate that the CPL can be created rapidly and the cake layer formation is the dynamic balance process of growth and erosion in the process of UF. The key factor affecting on the dielectric spectrum of UF system is the electrical properties of the CPL and the cake layer. In comparison to the results of dielectric measurement, the simulations indicate that the model proposed in this work is valid and reliable to some degree for describing and explaining the dielectric relaxation phenomenon in UF system. It is very important to further understand the fouling behavior of membrane surface and optimize the controlling techniques of membrane fouling in the process of UF.
文摘Digital microfluidics （DMF） is a versatile microfluidics technology that has significant application potential in the areas of automation and miniaturization. In DME discrete droplets containing samples and reagents are controlled to implement a series of operations via electrowetting-on-dielectric. This process works by apply- ing electrical potentials to an array of electrodes coated with a hydrophobic dielectric layer. Unlike microchannels, DMF facilitates precise control over multiple reaction processes without using complex pump, microvalve, and tubing networks. DMF also presents other distinct features, such as portability, less sample consumption, shorter chemical reaction time, flexibility, and easier combination with other technology types. Due to its unique advantages, DMF has been applied to a broad range of fields （e.g., chemistry, biology, medicine, and environment）. This study reviews the basic principles of droplet actuation, configuration design, and fabrication of the DMF device, as well as discusses the latest progress in DMF from the biochemistry perspective.
基金the National Natural Science Foundation of China(Grant No.50103010)the Education Department of Zhejiang Province(No.20071157)for supporting this work.
文摘Using poly(amic acid)(PAA)as a precursor followed by thermal imidization,the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process.The influence of processing factors,such as particle size,distribution mode and polymerization method on dielectric prop-erties was studied.Results revealed that the dielectric constant(ε)of the composite film increased by using bigger fillers or employing in situ polymerization and bimodal distribution.When the composite film contain-ing 50 Vol-%of BaTiO3 with size in 100 nm was pre-pared via in situ process,its dielectric constant reached 45 at 10 kHz.
