Droplet Charging Induced By Contact Electrification And Electrostatic Induction And Research On Its Application

Charged droplets have gained growing attention over the past few years.Because the unique physicochemical reactions at the interface of these charged droplets,it has lots of emerging applications and plays a vital part in them.For example,electricity generation,electrostatic spraying,accelerating fine chemical reactions,nanoscale material manufacturing,microfluidic systems and so on.In addition to these beneficial technological applications,such contact electrification may also have adverse consequences,such as reducing the success rate of pharmaceutical processes,reducing the efficiency of industrial production,and producing expensive disposal costs.In addition,if excessive charge accumulates on the material surface,gas will break down,generating sparks,which will cause combustible explosion,and damage the electronic components,etc.Therefore,it is very crucial to flexibly control and meter the charge amount,which is generated during contact.In the past,there are many methods to produce charged droplets,such as making use of the high voltage spray,passing droplets through microtubule,etc.However,such methods usually require external energy input or expensive equipment,and are unable to accurately control the droplet charge amount and charge type.Different from the conventional approaches,we put forward an experimental plan derived from the solid-liquid interface effect,namely Contact Electrification(CE),to generate charged droplets at a lower cost more accurately,and to regulate the charged amount and charged type.The applications of droplet in self-assembly,transportation,electricity generation and other fields were studied.The major experimental finding outcomes and substances are shown as below:(1)The droplet after solid-liquid separation obtain positive charge and the substrate obtain negative charge through the impacting,sliding,rolling and other behaviors between the droplet and the superamphiphobic surface.Using a pre-charged superamphiphobic substrate as an electret,negatively charged droplets are generated by electrostatic induction.And by changing the experimental conditions,such as droplet weber number,sliding distance,induction distance between liquid phase and electret,surface charge density of electret and other conditions to achieve accurate control of droplet charge amount and charged type.At the same time,this paper also changes the liquid type,solution concentration,times of impact,substrate temperature,droplet volume and other conditions,to explore the charging mechanism and diversity of droplet regulation.(2)So as to delve into the application of charged droplet in practical technology and industry,this paper provides a facile and low-cost strategy for droplet directional transportation.At present,the main methods used to manipulate the droplet are hydrodynamic stress,electrodynamic mechanics,magnetism,acoustics,setting specific geometric channels and so on.However,most of these methods require external mechanical energy or active parts,which are complicated to operate and cannot control the droplet flexibly.The repulsive and attractive interactions between droplets with the same and opposite charges or between charged droplets and electrets are used to enable the droplets to be transported spontaneously or rapidly assembled into highly ordered arrays.Finally,based on the principle of contact electrification and electrostatic induction,a simple micro chemical reactor driven by charged droplets and a nano-generator driven by water are fabricated,and their working principles are analyzed.