One of the vital functions of naturally occurring cilia is fluid transport.Biological cilia use spatially asymmetric strokes to generate a net fluid flow that can be utilized for feeding,swimming,and other functions.B...One of the vital functions of naturally occurring cilia is fluid transport.Biological cilia use spatially asymmetric strokes to generate a net fluid flow that can be utilized for feeding,swimming,and other functions.Biomimetic synthetic cilia with similar asymmetric beating can be useful for fluid manipulations in lab-on-chip devices.In this paper,we demonstrate the microfluidic pumping by magnetically actuated synthetic cilia arranged in multi-row arrays.We use a microchannel loop to visualize flow created by the ciliary array and to examine pumping for a range of cilia and microchannel parameters.We show that magnetic cilia can achieve flow rates of up to 11μl/min with the pressure drop of~1 Pa.Such magnetic ciliary array can be useful in microfluidic applications requiring rapid and controlled fluid transport.展开更多
Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.C...Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.Conventional TCDs use steady-state resistance(i.e.,temperature)measurements of a micro-heater.In this work,we developed a new measurement method and hardware configuration based on the processing of the transient response of a low thermal mass TCD to an electric current step.The method was implemented for a 100-μm-long and 1-μm-thick micro-fabricated bridge that consisted of doped polysilicon conductive film passivated with a 200-nm silicon nitride layer.Transient resistance variations of theμTCD in response to a square current pulse were studied in multiple mixtures of dilute gases in nitrogen.Simulations and experimental results are presented and compared for the time resolved and steady-state regime of the sensor response.Thermal analysis and simulation show that the sensor response is exponential in the transient state,that the time constant of this exponential variation was a linear function of the thermal conductivity of the gas ambient,and that the sensor was able to quantify the mixture composition.The level of detection in nitrogen was estimated to be from 25 ppm for helium to 178 ppm for carbon dioxide.With this novel approach,the sensor requires approximately 3.6 nJ for a single measurement and needs only 300μs of sampling time.This is less than the energy and time required for steady-state DC measurements.展开更多
基金We thank the USDA NIFA(grant#11317911)the National Science Foundation(CBET-1510884)for financial support
文摘One of the vital functions of naturally occurring cilia is fluid transport.Biological cilia use spatially asymmetric strokes to generate a net fluid flow that can be utilized for feeding,swimming,and other functions.Biomimetic synthetic cilia with similar asymmetric beating can be useful for fluid manipulations in lab-on-chip devices.In this paper,we demonstrate the microfluidic pumping by magnetically actuated synthetic cilia arranged in multi-row arrays.We use a microchannel loop to visualize flow created by the ciliary array and to examine pumping for a range of cilia and microchannel parameters.We show that magnetic cilia can achieve flow rates of up to 11μl/min with the pressure drop of~1 Pa.Such magnetic ciliary array can be useful in microfluidic applications requiring rapid and controlled fluid transport.
基金The sensor that was tested in this work is based on the patents:No.7,911,010,No.8,426,932 and No.8,884,382.
文摘Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.Conventional TCDs use steady-state resistance(i.e.,temperature)measurements of a micro-heater.In this work,we developed a new measurement method and hardware configuration based on the processing of the transient response of a low thermal mass TCD to an electric current step.The method was implemented for a 100-μm-long and 1-μm-thick micro-fabricated bridge that consisted of doped polysilicon conductive film passivated with a 200-nm silicon nitride layer.Transient resistance variations of theμTCD in response to a square current pulse were studied in multiple mixtures of dilute gases in nitrogen.Simulations and experimental results are presented and compared for the time resolved and steady-state regime of the sensor response.Thermal analysis and simulation show that the sensor response is exponential in the transient state,that the time constant of this exponential variation was a linear function of the thermal conductivity of the gas ambient,and that the sensor was able to quantify the mixture composition.The level of detection in nitrogen was estimated to be from 25 ppm for helium to 178 ppm for carbon dioxide.With this novel approach,the sensor requires approximately 3.6 nJ for a single measurement and needs only 300μs of sampling time.This is less than the energy and time required for steady-state DC measurements.
