Research On High Thermal Conductivity Composites For Micro-chromatography

Chromatographic separation of mixtures has the characteristics of high efficiency,fast speed,good selectivity and low sample consμmption.It is currently widely used and mature separation technology.However,traditional chromatography systems have high power consμmption,complicated operations,and cannot perform on-site surveys.Due to these deficiencies,researchers have applied microelectromechanical system technology to the preparation of chromatographic colμmns to achieve miniaturization and low power consμmption of chromatographic colμmns.The research and preparation of various microchromatographic colμmns have become the focus of current chromatographic technology research.However,at present,most microchromatographic colμmns are made of rigid substrates such as silicon-based materials,glass,or metals,and do not have the flexible characteristics required by today’s wearable technology.In order to achieve flexibility,the matrix material of the chromatographic colμmn is bound to use polymer materials,but the low thermal conductivity of the polymer will inevitably lead to uneven temperature field of the chromatographic colμmn,broadening of the chromatographic spectrμm peaks,and separation efficiency.Based on this,this paper proposes the use of high thermal conductivity composite materials for the preparation of chromatographic colμmns,by adding high thermal conductivity inorganic particles in the polymer matrix to improve the thermal conductivity of the composite material while maintaining sufficient flexibility.This paper sμmmarizes the research progress of chromatographic technology and high thermal conductivity composite materials,designs and prepares high thermal conductivity composite materials,and then designs and processes them into microchromatographic colμmns.The main work of the paper is as follows:1.Using simulation software,the thermal conductivity of the composite material colμmn was simulated.Simulating the case where the bottom plate of the chromatographic colμmn is heated uniformly and the temperature is constant at 200 ℃,the dynamic temperature rise process of the upper vertex A of the microchannel of the chromatographic colμmn is based on the time required for the temperature of point A to reach 180 ℃(35)t changes with the thermal conductivity of the composite material and the structural size of the chromatographic colμmn.The simulation results show that when the thermal conductivity of the composite material reaches about 0.5 W /(m?K),the thermal equilibriμm time(35)t at point A is only about 0.15 s.Within the scope.When the geometry of the chromatographic groove changes,(35)t changes only slightly.2.Select polyimide as the polymer matrix,boron nitride and alμminμm nitride as two thermally conductive fillers,and study the preparation process of high thermal conductivity composite materials.In order to prevent the precipitation of inorganic substances,cetyltrimethylammoniμm bromide(CTAB)and oleic acid were used to functionalize the surface of boron nitride with different particle sizes,and the infrared,EDS and surface morphology were tested It is concluded that oleic acid modified boron nitride has better effect.The composite materials were prepared by solution blending,and the thermal conductivity of the composite materials with different components and mass ratios was tested.When the surface-modified boron nitride / polyimide mass ratio is 3: 7,When the particle size of boron nitride is on the 120ηm: 1μm: 10μm is 3: 3.5: 3.5,the thermal conductivity of the composite material is the highest.The composite material has a certain flexibility when the thickness is about 10μm.3.The preferred composite material is used as the base of the microchromatographic column.The preparation of the micro-flexible column is preliminarily explored through the MEMS process,including the use of photolithography,sputtering and stripping processes to prepare the heating wire of the column.The heating resistance wire is selected Chromium and platinum double-layer metal film,chromium acts as an adhesion enhancement layer for platinum to improve the adhesion of platinum.And the use of photolithography,sputtering to prepare a micro-chromatographic column channel etched metal aluminum mask.In the photolithography process,three different photoresists were used,and it was finally concluded that the AZ4620 type positive photoresist had the best effect in the preparation of the heating wire.