Research On Fabrication Of SU-8Micro/Nano Fluidic Channels

Recently, polymer Micro/nanofluidic devices allow the discovery of a range of new phenomena, because the channel dimension is approaching the scale of macromolecules or nanoparticles dissolved or mixed in fluid, fluidic transport through Micro/nanochannels offers a new insight into the fundamental nanoscale liquid flow behavior, paving the way to develop tools for manipulating DNA and proteins separation, drug delivery technology, life science, ion transport, electrophoresis and electroosmosis system and other important applications.In creating nanofluidic devices process, the fundamental challenges are to reduce and control the size of nanoscale trenches and seal these trenches to complete functional nanochannels at high resolution and low cost. Among the polymeric materials that have been used for Micro/nanofluidic system, SU-8photoresist is a highly desirable polymer for making microfluidic channels because of its good chemical resistance, mechanical strength, optical transparency and excellent capability for Micro/nanofabrication. However, due to the limits of manufacture SU-8nanostructure using conventional lithography methods, few studies using SU-8as structural materials to fabrication nanochannels. This thesis focuses on the fabrication of SU-8Micro/nanochannel, the subject matter of the thesis are as the follows:(1) Research on fabrication of nanoimprint mould:The smooth silicon-on-insulatro (SOI) mould is fabricated by holographic method combined with wet anisotropic etching. Holographic method can make narrow, dense and multiple continuous lines over centimeter lengths and wet anisotropic etching can eliminate line-edge-roughness (LER) and make the line nearly atomic-scale smoothness. Then the mould is used as imprint mould for faithfully imprint of SU-8. The PDMS soft mould also be fabricated by casting methods. The soft mould permits SU-8UV cured patterning and easily peeled off from SU-8structures, making convenience for free-standing SU-8nanofluidic system fabrication.(2) Research on thermal bonding technology:SU-8nanochannel is fabricated by thermal bonding, the tolerance of the process parameters greatly improving by using two layers of SU-8as a bonding layer. The advantage of this process is that the nanochannel depth can be adjustable simply by controlling the thickness of adhesive layer as well as imprint depth.(3) Research on other controllable channel sealing technology:Nanochannels with well-controlled dimensions in large area is fabricated by using a combined NIL and angled physical vapor deposition (PVD). The advantage of this process is that the line width can be adjustable simply by controlling the deposition as well as the imprint depth. This approach is capable of generating ultra small line pattern, which go beyond the limitation of orginal line width. Micro/nanofluidic channel is also sealed by a new sacrificial layer etching method. The etching method is suitable for fabricating the whole dimension channel ranging from micrometers to nanometers and the size of the channel is controlled by RIE process.(4) Nano fluidic system is fabricated by novel hybrid mask-mould (HMM) lithography and thermal bonding using SU-8. With the HMM lithography, the protrusions of channels and reservoir patterns can be replicated in one step. Free-standing SU-8nanofluidic system is designed and fabricated by using PDMS soft mould and PDMS sacrificial layer. Finally, the fluidic flow velocity in nanochannels is tested by dilutied red ink, shows that the red ink flow rate in nanochannels will faster if smaller contact angle of channel materials and greater the hydraulic radius were received.