Controlling Study Of Capillary Flows In Microfluidic Devices With Spacer Structures

Microfluidics offers many advantages in the fields of biology,chemistry and biomedicine with applications such as microreaction systems,medical diagnostics,drug discovery,in vitro diagnostics,drug delivery,sample preparation for biological/chemical analysis and genetic analysis.Integrated automated control of small liquid samples in chip form is also an increasingly important topic in(bio)chemical analysis in environmental and industrial processes as well as in the medical field.Liquid control in microchannels plays a crucial role in microfluidic devices,e.g.for lab-on-a-chip and point-of-care applications.Capillary microfluidics has attracted a great deal of attention because it is self-powered and is particularly advantageous when used in passive devices.Based on the capillary flow theory,the relationship between capillary flow length and time in two rectangular cross-section microchannels is derived,and the influence of capillary flow length and channel width ratio on the time difference between two capillary flows is analyzed.The measured volume-time curves of the flowing liquid are in good agreement with the calculated results;by designing and conducting several capillary flow control experiments,the waiting phenomenon of capillary flow in multiple channels is verified.The specific content of this paper is divided into four parts: in the first part,the research background and significance of this topic are introduced,and the main research content of this paper is introduced,as well as the existing research status of the topic-related content,mainly for the theoretical,experimental,and numerical simulation of capillary flow in microfluidic devices;in the second part,the study of capillary flow in microchannels is outlined from three aspects: theoretical,experimental,and numerical simulation The second part outlines the study of capillary flow in microchannels from theoretical,experimental and numerical simulations.In the third part,the relevant theoretical derivations are carried out to elucidate the flow phenomena and the theoretical reasons for the capillary flow time difference and waiting behavior in two or more channels.In the fourth part,the experimental equipment and apparatus used in this experiment are introduced,the experimental results are analyzed and discussed in comparison with the numerical simulation results obtained from the theory in the third part,and the results data are processed in four main directions,such as contact angle and capillary force analysis,estimation of liquid flow output,changing contact angle model and synchronization and control of capillary flow.Based on the results introduced in the process of the research,a simple porosity measurement method was found during the research.In addition,the amount of liquid flowing out of the waiting channel out of the waiting channel is estimated and verified.Then,a model for the contact angle variation during synchronization is derived and validated.Finally,this paper conceptualizes a series of studies on capillary flow control with different spacer designs and conducts an experiment to study the dynamic behavior of some capillary flows by adding many spacers to the microchannel,this study expands the application of capillary microfluidics.