Manipulation And Experiment Research Of Surface Modified Particles In Microfluidic

A number of natural or artificial self-generated micro-motor motion phenomenonexist in the micro-nano system. Synthetic micro-and nano particles gain energy fromthe surrounding fuel solution to drive itself to move continuously, which is a typicalmicro-motor’s self-propulsion motion. In recent years, this motion shows a potentialapplication value in the fields, such as biological sensing, functional materials, targeteddrug delivery, condensed matter physics.The synthetic Pt-SiO2type Janus particles use Pt-coated hemispheres todecompose the H2O2fuel and to establish a non-symmetric molecules numberconcentration gradient on the surface of particles to form continuous self-propulsionmotion. However, its self-propulsion motion behavior has great randomness, whichrestricts its practical application. Achieving precise control of its movement directionwill greatly improve this situation. This paper explored how to use intermittent restrainthe randomness of self-propulsion motion by applied electric field and to achieve itsback and forth shuttling motion.The self-propulsion mechanism and movement characteristics of Janus particle wasanalysed by the theoretical method. The self-propulsion includes three stages, that isclassic Brownian motion, self-propulsion motion, quasi-Brownian motion for Janusparticle. Self-propulsion motion has good directionality when the movementcharacteristic time is in the range of T R. Here, Tis the translationalcharacteristic time, Ris the rotation characteristic time. Then, the relationship of CMfactor versus electric frequency was calculated by Matlab software. The spatial electricfield distribution of interdigital electrode was analysed by numerical simulationsoftware COMSOL Multiphysics. Hereafter, dielectric response of SiO2and Janus particles were studied on the interdigital electrode strip experimentally, Janus particleswere attracted to the electrode edge and presented pDEP under high-frequency electricfield, which confirmed theoretical analysis. Particularly, Janus particles presented stablestatus that Pt-coated hemisphere opposite to the electrode and SiO2side point toelectrode. Its surface electric potential energy was calculated by numerical calculationwhen the interface of Pt and SiO2versus electrode set up different angle. It possessedthe lowest electric potential energy when the angle is60,which explained themechanism of the posture.Finally, the directional characteristic of self-propulsion and dielectric responsewere switched alternately to achieve reciprocation back and forth of Janus particle onthe electrode with a certain electric frequency and switching cycle. This study resultswill promote the application of Janus particles,which carry drugs along designatedroutes to the destination in the biomedical field.Mechanical properties of single-molecule DNA will promote the study of it’s geneexpression."Particle-DNA-Particle" is an effective method in the study of single DNAmolecule, which was formed by polymerase chain reaction and non-specific reaction ofbiotin versus streptavidin and digoxin versus anti-digoxin. This paper attempts to lockone microsphere on the substrate in micro-pipeline by the non-specific reaction.Afterwards, another microsphere motion was manipulated in order to study the repeatedstretch characteristics of DNA by oscillatory flow. Eventually, the elasticity coefficientof DNA was estimated, which is agreement with the order of magnitude.