| As a type of portable,eco-friendly,safe and highly efficient experimental platform,multifunctional microfluidic chips,also referred to as lab-on-a-chip systems,have attracted enormous research interest in recent decades due to their promise in both fundamental science and practical applications,ranging from chemical experiments,environmental monitoring,biological assays,and tissue engineering to medical diagnosis and therapeutics.Currently,by integrating various micro-scale components on a microfluidic chip,multiform experimental procedures,such as temperature regulation,nanoparticle synthesis,molecular detection,and cell manipulation,can be implemented in a controlled fashion.From a technical point of view,the rapid progress in microfluidic chip technology is driven by the constant advances in nanotechnology.As a typical example,well-developed semiconductor processing techniques enable the facile manufacturing of various microfluidic chips.Complex microfluidic channels with different sizes and designable shapes can be readily fabricated in a wide range of materials through the combined technologies of lithography and etching.To pursue greater resolution or a controllable height-width ratio,deep reactive-ion etching(DRIE),inductively coupled plasmas(ICP)and other advanced processing techniques have also been used to fabricate microfluidic chips.Recently,to further enhance production efficiency,imprinting and soft lithography technologies have been successfully adopted to manufacture polymer microfluidic chips by duplicating hard templates machined using traditional methods.Despite pronounced success in manufacturing microfluidic chips,the progress in multifunctionality remains restricted by the lack of technology that permits the flexible integration of various functional components;this significantly limits broad application.First,microfluidic chip manufacturing is generally based on conventional planar processes,such as lithography and imprinting.However,the integration of functional components requires precise fabrication of microstructures within microfluidic channels,which are not flat.In addition,traditional methods can process only two-dimensional(2D)microstructures;the integration of three dimensional(3D)functional micronanostructures within microfluidic chips is still challenging.Moreover,materials suitable for processing are limited to polymers,glass or silicon,which cannot meet the demands of multiform functional materials.All of these obstacles have become bottlenecks restricting progress in the exploration,development and application of multifunctional microfluidic chips.In recent years,laser processing technologies have emerged as an appealing alternative to conventional semiconductor processing techniques,making it possible to integrate various functional devices into microfluidic chips.To achieve on-chip laser processing(OCLP),several photochemical and photophysical schemes,including laser ablation as a subtraction-type process,and photopolymerization,photoreduction of metal ions and photodynamic assembly of nanoparticles as addition-type processes,have been successfully developed for on-chip structuring of various functional materials such as glasses,polymers,metals,biomaterials and nanomaterials.Compared with traditional micronanofabrication technologies,OCLP has the distinct advantages of high precision,the ability to use multiform processing-capable materials,and sitespecific fabrication.Specifically,when an ultra-short-pulse laser has been adopted for on-chip processing,thermal effects can be significantly suppressed,and thus the spatial resolution can be further improved.As a typical example,femtosecond laser on-chip processing enables 3D fabrication with sub-50 nm precision at any desired position,and thus has substantial potential in the development of multifunctional microfluidic chips.In this paper,we report on-chip laser processing multifunctional microfluidic chips:1.Microvalves are important components in microfluidic chips.Especially intelligent microvalves that can respond to the change of microenvironment would adjust the flux of microfluids.Based on femtosecond laser direct writing technology(Fs LDW),several intelligent solvent response microvalves have been fabricated.The sizes and morphologies of microvalves are designable according to the requirement of microfluidic chips.Additionally,controllable assembly of silver nanoparticles(Ag NPs)for patterning of silver microstructures is reported here.The assembly is induced by femtosecond laser photodynamic assembly(Fs LPDA).A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ?190 nm.Taking advantage of the ‘direct writing' feature,three microelectrodes have been integrated with a microfluidic chip;two silverbased microdevices including a microheater and a catalytic reactor have been fabricated inside a microfluidic channel for chip functionalization.The Fs LPDA-induced programmable assembly of Ag NPs may open up a new way to the designable patterning of silver microstructures toward flexible fabrication and integration of functional devices.What's more,Fs LPDA also enables to flexibly integrate magnetic NPs on microorganisms and fabricate magnetically controllable Daphnia,which is promising for biochips.In principle,Fs LPDA could assemble any kind of NPs into microfluidic chips regardless of their chemical compositions,further enriching the function of microfluidic chips.2.Microfluidic chips are miniaturized experimental platforms,enables extremely sensitive,efficient,low-consumption,safe and environment-friendly biochemical reactions.However,coupled auxiliary devices(e.g.pressure pumps for sampling,microscope for observation)are generally necessary for microfluidic chips,which makes it impossible for microfluidic chips to be a portable experimental platform.By employing integrated components that could transfer external fields to fluidic driving forces,digital microfluidic chip can manipulate droplets samples in a controlled fashion.However,the introduction of external fields,such as electrical field,thermal gradient,magnetic field,optical field and mechanical vibration,not only brings undesired influence to the reaction system,but also involves complex equipment inevitably,making digital microfluidic chips an in-lab-only device.Here we manufacture a gravity driven superhydrophobic embossed microfluidic chip toolkit through laser engraving and modifying,which could flexibly control microdroplets for delivering,screening,splitting,merging,shocking,jumping,and integrated manipulations.Based on simple assemblages of modules in the toolkits,various experiments,such as optical detection,biolabeling and chemical synthesis are achieved.We believe this gravity driven embossed microfluidic chip toolkit is a promising portable biochemical experiment platform.3.Fs LDW is known as a 3D micronanofabrication craft with high resolution.However,the efficient of Fs LPDA is low,due to the point-to-point scan manner.Here 3D ultralong microfibers are fabricated with high efficient through microfluidic chip aided femtosecond laser direct writing(MAFs LDW).Femtosecond laser that is tightly focused into a microchannel with continuous photosensitive prepolymer flow,can fabricate ultralong microfibers through multiphoton absorption.Many 2D,3D ultralong microstructures are designed.Compared with other crafts,MAFs LDW is a novel and distinctive micro/nano processing technology.To conclude,I have integrated several functional components including microvalves,microheaters,microreactors,magnetic microorganisms,through Fs LDW,Fs LPDA to enrich the property of microfluidic chips.Then embossed microfluidic chip that can flexibly manipulate droplets are machined via laser engraving and modifying.Besides,a novel micro/nano processing technology called MAFs LDW is founded,and interesting ultralong microfibers are created.All these work will promote the development of microfluidic chips and laser micronanofabrication. |
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