Fabrication Of Micro-/nano-functional Structure Arrays Based On Dip Pen Nanolithography And Microcontact Printing

Micro/nano functional materials that are arranged orderly on a large scale usually possess unique light and electricity properties and enable high-throughput signal output,thus play an important role in the fields of integrated circuits,optoelectronic devices and biological analysis.Recently,increasing attention has been paid to the preparation of large-area functional structure arrays and the regulation of size,interspacing and properties of the corresponding materials.At present,the traditional preparation methods of functional structure array mainly include optical etching,electrochemical etching and 3D printing.However,these approaches face challenges such as sophisticated operation,high cost and difficulty in large-scale production.Therefore,the development of low-cost preparation method with simple operation is of great significance in building large-area functional arrays with controllable structural and composition.Dip pen nanolithography(DPN),based on unique nanometer etching instruments,allows simple,efficient,intelligent and controllable printing,and therefore is able to fabricate micro/nanostructure arrays with high resolution.Unfortunately,this technology has not found wide applications in China.Microcontact printing(?CP),on the other hand,relying on elastic polymer needle tips for material transmission and printing with low cost,has already made remarkable process in the field of micro/nano manufacturing.In this thesis,we established simple and efficient fabrication approach based on DPN and micro contact printing and successfully obtained Polydopamine(PDA)arrays.With this platform,the functional array structures such as biological chips were constructed through the interaction of PDA with biomolecules and metal salt.This thesis first proposed of the fabrication of PDA micro/nano arrays based on micro-contact and DPN technology and further realized the regulation of array size and spacing on a series of common substrates.PDA arrays were then incubated with a variety of biomolecules and cells,enabling the construction of biochips that are compatible with many bio-species,which are promising in the applications of biological analysis,drug screening,etc.Compared with the traditional biochips that usually target with one type of biomolecule,our strategy can generally apply to a variety of common biomaterials,such as nucleic acids,proteins,cells,etc.Moreover,the ability of PDA to reduce and chelate metal ions can direct the growth of thin film structures assembled by metal nanoparticles(abbreviated as metal nanoparticle film(MNF)in the later text),allowing the construction of MNF arrays.In our study,the ordered MNF arrays were observed to show obvious Raman enhancement,thus,they are expected to construct devices for optical analysis and detection.Compared with traditional preparation methods,our strategy is simple and efficient,with minimum damage to the resulting metal nanoparticles.The key points of this thesis are summarized below:(1)The dopamine drop arrays was printed by DPN and micro-contact printing techniques,which were subjected in the alkaline atmosphere of ammonia at room temperature to allow in-situ polymerization.Compared with conventional polymerization procedure that treated dopamine by immersing it in an alkaline Tris buffer solution,the current method has reduced the polymerization time from 18-24 hours to only 8 hours.The surface morphology of PDA was then characterized by SEM and AFM,which shows that each PDA features has formed film-like structures with low surface roughness and uniform size.Furthermore,the composition and structure of PDA were analyzed using Raman,Infrared and X-ray photoelectron spectroscopy,confirming that PDA film arrays were successfully prepared using DPN and microcontact printing.(2)The prepared PDA microarrays were incubated with a variety of biomaterials,such as nucleic acids,proteins,and cells.Observing under a fluorescence microscopy,the corresponding biomaterial array structure was successfully formed,indicating that the prepared PDA array can interact with various biomaterials for the construction of biochips with broad applications.In addition,we can successfully construct single cell arrays with large area by regulating the size of the PDA array.Moreover,we are able to control the adhesion state of a variety of cells on the PDA surfaces by using different treatment methods to the substrate.(3)By incubating the PDA chip with solutions containing metal precursors,we found that PDA film can direct the growth of gold and silver nanoparticles into a thin film structure,forming arrays of nanoparticle assembled thin films.SEM and AFM characterization proved that the nanoparticles and film-like structures have uniform morphology and size.Subsequently,the MNF arrays were used in Raman analysis and the catalytic reduction of 4-nitrophenol.The results showed that the prepared metal nanoparticle film array show excellent Raman enhancement and catalytic performance.