Huang Xiaolu, Bauder Tyler, Do Truong, Suen Hawke, Boss Connor, Kwon Patrick, Yeom Junghoon
Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824, USA.
Department of Electrical Engineering, Michigan State University, East Lansing, MI 48824, USA.
Sensors (Basel). 2019 Jun 19;19(12):2748. doi: 10.3390/s19122748.
A conventional approach to making miniature or microscale gas chromatography (GC) components relies on silicon as a base material and MEMS fabrication as manufacturing processes. However, these devices often fail in medium-to-high temperature applications due to a lack of robust fluidic interconnects and a high-yield bonding process. This paper explores the feasibility of using metal additive manufacturing (AM), which is also known as metal 3D printing, as an alternative platform to produce small-scale microfluidic devices that can operate at a temperature higher than that which polymers can withstand. Binder jet printing (BJP), one of the metal AM processes, was utilized to make stainless steel (SS) preconcentrators (PCs) with submillimeter internal features. PCs can increase the concentration of gaseous analytes or serve as an inline injector for GC or gas sensor applications. Normally, parts printed by BJP are highly porous and thus often infiltrated with low melting point metal. By adding to SS316 powder sintering additives such as boron nitride (BN), which reduces the liquidus line temperature, we produce near full-density SS PCs at sintering temperatures much lower than the SS melting temperature, and importantly without any measurable shape distortion. Conversely, the SS PC without BN remains porous after the sintering process and unsuitable for fluidic applications. Since the SS parts, unlike Si, are compatible with machining, they can be modified to work with commercial compression fitting. The PC structures as well as the connection with the fitting are leak-free with relatively high operating pressures. A flexible membrane heater along with a resistance-temperature detector is integrated with the SS PCs for thermal desorption. The proof-of-concept experiment demonstrates that the SS PC can preconcentrate and inject 0.6% headspace toluene to enhance the detector's response.
制造微型或微尺度气相色谱（GC）组件的传统方法依赖于硅作为基础材料，并采用微机电系统（MEMS）制造工艺。然而，由于缺乏坚固的流体互连和高成品率的键合工艺，这些器件在中高温应用中常常失效。本文探讨了使用金属增材制造（AM）（也称为金属3D打印）作为替代平台来生产能够在高于聚合物承受温度的条件下运行的小型微流控器件的可行性。粘结剂喷射打印（BJP）作为金属增材制造工艺之一，被用于制造具有亚毫米内部特征的不锈钢（SS）预浓缩器（PC）。预浓缩器可以提高气态分析物的浓度，或用作气相色谱或气体传感器应用中的在线注射器。通常，通过粘结剂喷射打印制造的部件具有高度多孔性，因此常常会渗入低熔点金属。通过向SS316粉末中添加烧结添加剂，如氮化硼（BN），可降低液相线温度，我们在烧结温度远低于不锈钢熔点的情况下生产出接近全密度的不锈钢预浓缩器，重要的是没有任何可测量的形状变形。相反，没有添加氮化硼的不锈钢预浓缩器在烧结过程后仍然多孔，不适合流体应用。由于不锈钢部件与硅不同，它与机械加工兼容，因此可以进行修改以与商业压缩接头配合使用。预浓缩器结构以及与接头的连接在相对较高的工作压力下无泄漏。一个柔性薄膜加热器以及一个电阻温度探测器与不锈钢预浓缩器集成在一起用于热解吸。概念验证实验表明，不锈钢预浓缩器可以预浓缩并注入0.6%的顶空甲苯以增强探测器的响应。
