Study Of Blood Cell Separation And Disruption Microfluidic Chips Towards Space-station Applications

In the space environment,microgravity,high radiation,rhythmic change,noise and other factors may adversely affect the health of astronauts,therefore,it is necessary to regularly monitor the health indicators for long-term on-orbit astronauts.The biochemical index assay based on body fluids(blood,urine,saliva,etc.)is the most important approach for biochemical index test,as sample collection is easy and testing fast.Sample pretreatment should be carried out before testing,such as separating white blood cells(WBCs)from whole blood and disrupting cells.With the advantages of small size,low sample consumption,short analysis time,simple operation and low power consumption,microfluidic chips are very suitable for medical examination in aerospace.In this dissertation,microfluidic blood cell separation and cell disruption chips are studied for aerospace applications.This dissertation reports on a clogging-free microfluidic cell separation chip,which features with an integrated bidirectional micropump and a microporous filtration membrane,and the chip works with cross-flow filtration mode combining with dead-end filtration mode.The integrated bidirectional micropump enables the fluid to flow back and forth repeatedly,which flushes the filtration membrane to clear the filtration micropores for further filtration and implements multi-filtration.The key parameters such as flow rate and micropore size are optimized by experiment and on-chip multi-filtration is implemented to enhance the separation performance.The chip could recover 72.1% WBCs with an over 232-fold enrichment ratio and a 15.1% purity at a throughput of 37.5 μl/min,meanwhile,99.7% red blood cells(RBCs)are removed.Then,the dissertation presents a bubble-free and clogging-free microfluidic cell separation chip with high throughput.By integrating a hydrophobic porous membrane on the top of the channel in the filtration region and optimizing the flow rate for degassing,more than 90.0% bubbles with a broad range of sizes are efficiently removed in the filtration region,while more than 88.8% bubbles are removed in the output sample.The bubbles can also be removed when the chip is upside down.By removing bubbles,the separation efficiency and operational reliability are improved.After 8 cycles of multifiltration,WBCs were effectively separated from whole blood with a 396-fold enrichment ratio,a 70.6% recovery rate and a 23.3% purity,and 99.8% RBCs are removed.300 μl whole blood are processed in 460 s,equivalent to a throughput of 39.1 μl/min.Benefitting from the degassing function,the bubble percentage in the output sample is less than 0.82%.All the separation processes,including sample loading,separation,degassing and sample collection,are automatically controlled without the requirement of external fluid-driving source.A pump-on-chip cell disruption microfluidic chip is demonstrated for mechanical cell disruption.The chip features with an on-chip micropump for mechanical cell disruption and sample transport.Cells will be crushed down by the steel balls of the micropump and the compressive stress.50 μl cell sample can be effectively lysed through on-chip multi-disruption in 36 s without introducing any chemical agent and suffering from clogging by cellular debris.Some key parameters for cell disruption such as steel ball pressing depth and chip bottom layer hardness are optimized.Circulating disruption step is repeated multiple times to implement on-chip multi-disruption for a better disruption effect.After 30 cycles of circulating disruption,80.6% and 90.5% cell disruption rates were achieved for HEK293 cell and human NK cell samples,respectively.A cell separation chip and a cell disruption chip for the body fluid pretreatment control instrument developed for aerospace applications are designed and fabricated.A package method of microfluidic pretreatment chips is develop for aerospace applications,which allows the chip to withstand a negative pressure as low as 10 Pa and the rapid reduction of environmental pressure.The performances of separation,cell disruption,degassing and quantitative delivering of the microfluidic pretreatment chips are tested,and the test results meet the project requirements.