It is obvious that the pressure gradient along the axial direction in a pipe flow keeps constant according to the Hagen-Poiseuille equation. However, recent experiments indicated that the distribution of the pressure ...It is obvious that the pressure gradient along the axial direction in a pipe flow keeps constant according to the Hagen-Poiseuille equation. However, recent experiments indicated that the distribution of the pressure seemed no longer linear for liquid flows in microtubes driven by high pressure （1-30MPa）. Based on H-P equation with slip boundary condition and Bridgman＇s relation of viscosity vs. static pressure, the nonlinear distribution of pressure along the axial direction is analyzed in this paper. The revised standard Poiseuille number with the effect of pressure-dependent viscosity taken into account agrees well with the experimental results. Therefore, the dependence of the viscosity on the pressure is one of the dominating factors under high driven pressure, and is represented by an important property coefficient α of the liquid.展开更多
The concept of using stimuli-responsive hydrogels to actuate fluids in microfluidic devices is particularly attractive,but limitations,in terms of spatial resolution,speed,reliability and integration,have hindered its...The concept of using stimuli-responsive hydrogels to actuate fluids in microfluidic devices is particularly attractive,but limitations,in terms of spatial resolution,speed,reliability and integration,have hindered its development during the past two decades.By patterning and grafting poly(N-isopropylacrylamide)PNIPAM hydrogel films on plane substrates with a 2μm horizontal resolution and closing the system afterward,we have succeeded in unblocking bottlenecks that thermo-sensitive hydrogel technology has been challenged with until now.In this paper,we demonstrate,for the first time with this technology,devices with up to 7800 actuated micro-cages that sequester and release solutes,along with valves actuated individually with closing and opening switching times of 0.6±0.1 and 0.25±0.15 s,respectively.Two applications of this technology are illustrated in the domain of single cell handling and the nuclear acid amplification test(NAAT)for the Human Synaptojanin 1 gene,which is suspected to be involved in several neurodegenerative diseases such as Parkinson’s disease.The performance of the temperature-responsive hydrogels we demonstrate here suggests that in association with their moderate costs,hydrogels may represent an alternative to the actuation or handling techniques currently used in microfluidics,that are,pressure actuated polydimethylsiloxane(PDMS)valves and droplets.展开更多
基金The project supported by the Chinese Academy of Sciences Major Innovation Project (KJCX2-SW-L2)the National Natural Science Foundation of China (10272107)The English text was polished by Yunming Chen
文摘It is obvious that the pressure gradient along the axial direction in a pipe flow keeps constant according to the Hagen-Poiseuille equation. However, recent experiments indicated that the distribution of the pressure seemed no longer linear for liquid flows in microtubes driven by high pressure （1-30MPa）. Based on H-P equation with slip boundary condition and Bridgman＇s relation of viscosity vs. static pressure, the nonlinear distribution of pressure along the axial direction is analyzed in this paper. The revised standard Poiseuille number with the effect of pressure-dependent viscosity taken into account agrees well with the experimental results. Therefore, the dependence of the viscosity on the pressure is one of the dominating factors under high driven pressure, and is represented by an important property coefficient α of the liquid.
基金We gratefully thank the Institut Pierre-Gilles de Gennes(IPGG)the French National Research Agency(ANR),EQUIPEX and LABEX IPGG(Grant Nos.ANR-10-IDEX-0001-02,ANR-10-LABX-31,PSL*)+1 种基金the China Scholarship Council(CSC),ESPCI,CNRS,PSLthe Ministry of Science and Technology of Thailand(MOST)for their financial support.
文摘The concept of using stimuli-responsive hydrogels to actuate fluids in microfluidic devices is particularly attractive,but limitations,in terms of spatial resolution,speed,reliability and integration,have hindered its development during the past two decades.By patterning and grafting poly(N-isopropylacrylamide)PNIPAM hydrogel films on plane substrates with a 2μm horizontal resolution and closing the system afterward,we have succeeded in unblocking bottlenecks that thermo-sensitive hydrogel technology has been challenged with until now.In this paper,we demonstrate,for the first time with this technology,devices with up to 7800 actuated micro-cages that sequester and release solutes,along with valves actuated individually with closing and opening switching times of 0.6±0.1 and 0.25±0.15 s,respectively.Two applications of this technology are illustrated in the domain of single cell handling and the nuclear acid amplification test(NAAT)for the Human Synaptojanin 1 gene,which is suspected to be involved in several neurodegenerative diseases such as Parkinson’s disease.The performance of the temperature-responsive hydrogels we demonstrate here suggests that in association with their moderate costs,hydrogels may represent an alternative to the actuation or handling techniques currently used in microfluidics,that are,pressure actuated polydimethylsiloxane(PDMS)valves and droplets.
