【作者】 孙蕾；

【导师】 吴东江；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2020， 博士

【摘要】 微纳流控芯片是将微米结构和纳米结构集成为一体的多功能芯片,在基因测序、生化分析和环境检测等方面展现出广阔的应用前景。目前,微纳流控芯片制造面临生产成本高、制作工艺复杂、加工周期长等难题。因此,探究微纳流控芯片的高效低成本制造方法具有重大的现实意义。鉴于SU-8光刻胶具有成本低、易于加工、机械强度高、化学性能稳定和生物兼容性好等优点,本文对SU-8微纳流控芯片的制造方法及相关理论进行了研究,主要内容包括以下几个方面:(1)硅纳米模具低成本制造方法及相关理论研究目前,SU-8微纳流控芯片中的纳米沟道通常是利用纳米模具通过热纳米压印技术获得的,因此,纳米模具制造是微纳流控芯片制造的关键步骤。本文提出了两种低成本制造大面积硅纳米模具的新方法。方法一利用倾斜蒸镀和等离子体刻蚀技术制造了硅纳米凹模具,通过研究光刻胶厚度、蒸镀角度和刻蚀时间对纳米凹槽尺寸的影响,制造了不同尺寸的硅纳米凹模具,其中纳米结构最小宽度为108 nm。方法二利用接近式紫外曝光和深反应离子刻蚀制造了硅纳米凸模具,基于光的衍射理论分析了接近式曝光图形缩小的原理,优化了曝光、显影、后烘和深反应离子刻蚀等各项工艺参数,制造了不同尺寸的高质量硅纳米凸模具,其中纳米结构最小宽度为263 nm。这两种加工方法均可以实现4英寸硅纳米模具制造,纳米结构均匀性良好,且不依赖昂贵的加工设备,生产成本低、工艺简单、制作周期短。(2)SU-8光刻胶热压印填充行为研究通过测量SU-8光刻胶的应力松弛曲线和流变曲线,分析了不同温度下SU-8光刻胶的流变特性。结合热纳米压印实验讨论了不同压印温度下SU-8光刻胶的填充行为,在优化的压印参数(温度85℃、时间3 min)件下,制造了复制误差仅为2.8%的高精度纳米沟道。该研究为提高SU-8微纳流控芯片加工精度奠定了基础。(3)二次浇注和紫外热纳米压印制造跨尺度微纳流控芯片工艺研究利用硅纳米凹模具,通过二次浇注聚二甲基硅氧烷(PDMS),制造了 PDMS跨尺度微纳模具,并利用该模具采用紫外热纳米压印的方法制造了 SU-8跨尺度微纳流控芯片。优化了曝光时间、键合温度和氧等离子体处理功率及时间等工艺参数,提高了跨尺度微纳米图形的加工精度,并通过荧光测试表征了芯片的键合质量。该方法步骤简单、适用性强、工艺稳定性好、芯片成品率高,因此降低了跨尺度微纳结构的加工难度和生产成本,可用于实现批量化的跨尺度微纳器件制造。(4)薄膜生长和二次键合法分步制造微纳流控芯片工艺研究利用硅纳米凸模具通过热纳米压印制造了 SU-8光刻胶纳米沟道,利用生长聚对二甲苯(Parylene)薄膜法缩小了纳米沟道尺寸,并讨论了 Parylene沉积压力对薄膜粗糙度的影响。结合生长Parylene薄膜和二次键合法实现了通道最小宽度为100 nm以下的微纳流控芯片制造,并优化了键合温度和氧等离子体处理参数,提高了芯片的键合强度,通过荧光测试表征了芯片的键合质量。该方法适合低成本批量化的微纳流控芯片制造。综上所述,本文通过SU-8微纳流控芯片制造方法及相关理论的研究,实现了低成本制造微纳流控芯片,为微纳流控芯片的制造方法提供了新的技术思路,同时也为推动微纳流控芯片的广泛应用提供了有力支撑。更多还原

【Abstract】 The micro-nano fluidic chips,which are integrated chips combining micro and nano structures,have exhibited appealing applications in the fields such as DNA sequencing,biochemical analysis,and environment detection.At present,the fabrication of micro-nano fluidic chips is hindered by its high-cost,complicated,and time-consuming processes.As such,the development of novel fabrication methods with low cost and high efficiency is of great practical significance.The advantages of SU-8 photoresist include high machinability,mechanical strength,chemical stability,bio-compatiblity as well as low cost.In this thesis,the fabrication methods and relevant theories of SU-8 micro-nano fluidic chips are studied.The main contents are summarized as follows:(1)Research on the low-cost fabrication methods and relevant theories of large-area silicon nano moldsThe nano channels on the SU-8 photoresist are realized by thermal nano imprinting with silicon nano molds.Consequently,the nano molds are critical to the fabrication of nano channels.Two low-cost novel fabrication methods for large-area silicon molds were proposed in this thesis:(a)Concave silicon molds were achieved by inclined deposition and plasma etching.The influence of photoresist thickness,evaporation inclination,and etching duration on the trench dimensions was discussed.The silicon nano molds with different sizes were fabricated,among which the minimum width was 108 nm.(b)Convex silicon molds were achieved by proximity ultraviolet(UV)lithography and deep reactive ion etching.The pattern-size reduction effect in proximity exposure was analyzed based on diffraction theories.By optimizing the parameters in the processes of exposure,development,post-baking,and deep reactive ion etching,nanoscale silicon ridges were fabricated with high precision.The achieved minimum width of nano ridges was 263 nm.Both methods are capable of fabricating silicon nano molds covering four-inch wafer with high uniformity,which are simple,efficient and free from costly equipment.(2)Research on the filling behavior of SU-8 photoresist in thermal imprintingThe stress relaxation curves and shear stress/rate flow curves were measured to analyze the temperature dependent rheological properties of SU-8 photoresist.The filling behavior of SU-8 photoresist was discussed based on thermal imprinting results at various temperatures.High-precision nano channels were fabricated with replication error of 2.8%at optimized thermal imprinting temperature of 85℃ and duration of 3 min,which paves the way for high-precision fabrication of SU-8-based micro-nano fluidic chips.(3)Research on the hybrid micro-nano fabrication method based on double-casting and UV thermal nanoimprintingWith concave silicon nano molds,polydimethylsiloxane(PDMS)hybrid micro-nano molds were fabricated by a double-casting method.Consequently,SU-8 hybrid micro-nano fluidic chips were realized by UV-thermal nano imprinting with the PDMS hybrid micro-nano molds.The quality of micro-nano patterns was improved by optimizing the parameters in exposure,bonding,and plasma treatment.The bonding quality of the chips was characterized by fluorescent tests.The proposed fabrication method is simple,universal,stable,and high-yield.Therefore,it lowers the difficulty and cost for manufacturing hybrid micro-nano structure and enables its batch production.(4)Research on the step-by-step micro-nano fabrication method based on thin film deposition and double-bondingSU-8 nano channels were fabricated by thermal nanoimprinting with convex silicon nano molds,and their widths were reduced by Parylene thin film deposition.The influence of deposition pressure on the roughness of Parylene thin films was investigated.Micro-nano fluidic chips with channel widths under 100 nm were achieved by the double-bonding method.The bonding strength were enhanced by optimizing the bonding temperature and plasma treatment parameters.The bonding quality of the chips was characterized by fluorescent tests.The proposed method is suitable for low-cost batch production of micro-nano fluidic chips.In summary,by studying the fabrication methods and relevant theories of SU-8-photoresist-based micro and nano structures,the micro-nano fluidic chips are realized at low cost in this thesis.The proposed novel fabrication roadmaps could provide strong support for the extensive applications of micro-nano fluidic chips.更多还原