Models to determine the process parameters required to sculpt desired micro-feature topographies on flat and curved surfaces using abrasive jet technology

由空气或水推动的小磨料颗粒的射流已经被用于改变工程表面的形貌多年。磨料射流技术（AJT）的最重要应用之一是作为微流体、微机电系统（MEMS）和光电子元件的低成本和快速微制造平台。拟议的研究将集中在两个AJT的为此目的：空气驱动磨料射流微加工（AJM）和磨料水射流微加工（AWJM）。这些技术的优点很多，但也许最重要的是它们可以在不产生热影响区的情况下进行加工，并且它们具有大多数竞争技术所没有的独特的定向蚀刻能力。例如，通道的传统各向同性湿法蚀刻导致单个基本U形微通道横截面。然而，AJT的定向蚀刻能力允许通过改变工艺参数（例如，喷射扫描速度和倾斜角度、颗粒尺寸等）来雕刻许多不同的形状。拟议的研究将利用这种独特的能力，使该技术用于制造新设备。 我们以前已经开发了各种材料的AJM的“表面演变”模型，可以预测加工形貌的发展，在一个最初的平面上的各种组合的工艺参数。然而，下一代微流体和MEMS器件将需要微加工3D（即非平面）组件，这是AJM尚未探索的领域，尽管它具有巨大的潜力。类似地，目前没有表面演变模型来预测使用AWJM的机加工形貌，AWJM是一种较新的工艺，由于磨料浆回流效应和缺乏掩模而与AJM有根本不同。通过与工业合作伙伴的独家协议，我们拥有一个带有独特微型喷嘴的AWJM装置，这将使我们能够在这一领域进行突破性的研究。 AJT的一个复杂因素是颗粒嵌入到表面的趋势，从而影响表面质量，侵蚀率，粗糙度等，目前，没有模型存在预测什么颗粒和工艺参数控制的程度，这种嵌入使用AJT加工金属时。拟议的研究的初始部分将集中在解决这些重要的缺点，AJT过程的建模。 表面演变模型是重要的，因为它们可以预测加工地形作为输入工艺参数的函数，然而，目前没有技术来解决逆问题，即预测雕刻特定期望的地形所需的工艺参数。 拟议的研究的最后一部分将解决这个重要的问题，这将允许使用AJT的特定所需的功能形状的造型。 换句话说，我们将开发的方法，允许输入（工艺参数）的表面演化方程，以确定在未来的某个时间（所需的横截面轮廓）的方程的一个理想的解决方案。由于表面演化偏微分方程是非线性的，不能用封闭形式求解，因此该问题具有挑战性。最初，将使用优化例程来确定最接近所需形貌的参数集。后来，新的技术雕刻所需形状的表面使用倾斜和垂直入射喷嘴的组合将开发。这些技术将为3D MEMS和微流体设备的设计开辟一系列新的设备设计机会，从而支持加拿大不断增长的微技术部门。

Jets of small abrasive particles propelled by air or water have been used for many years to modify the topography of engineered surfaces. One of the most important applications of abrasive jet technology (AJT) is as a low cost and rapid micro-fabrication platform for microfluidics, micro-electomechanical systems (MEMS), and opto electronics components. The proposed research will focus on two AJT's for this purpose: air driven abrasive jet micro-machining (AJM) and abrasive waterjet micro-machining (AWJM). The advantages of these technologies are many, but perhaps the most important are that they can machine without creating a heat affected zone, and that they have a unique directional etch capability that most competing technologies do not. For example, traditional isotropic wet etching of channels results in a single basic U-shaped micro-channel cross-section. The directional etch capability of AJT, however, allows the sculpting of many different shapes by changing the process parameters (e.g. jet scan speed and inclination angle, particle size, etc). The proposed research will exploit this unique capability, allowing the technology to be used in the manufacture of novel devices. We have previously developed "surface evolution" models for the AJM of a wide variety of materials that can predict the development of machined topography on an initially flat surface for various combinations of process parameters. The next generation of microfluidic and MEMS devices, however, will require micro-machining 3D (i.e. non-planar) components, an area that has not yet been explored for AJM, despite its great potential. Similarly, there is currently no surface evolution model to predict machined topography using AWJM, a newer process that is fundamentally different than AJM because of abrasive slurry backflow effects and the lack of a mask. Through an exclusive agreement with an industrial partner, we have an AWJM setup with a unique micro-nozzle that will allow us to do ground-breaking research in this area. A complicating factor for AJT is the tendency for particles to embed into the surface and thus affect the surface quality, erosion rate, roughness, etc. Currently, no model exists for predicting what particle and process parameters control the extent of this embedding when machining metals using AJT. The initial portion of the proposed research will focus on addressing these important shortcomings in the modeling of AJT processes. Surface evolution models are important because they can predict machined topography as a function of input process parameters; however, there are currently no techniques to solve the inverse problem, i.e. predicting the process parameters necessary for sculpting particular desired topographies. The final portion of the proposed research will tackle this important problem that would allow the sculpting of particular desired feature shapes using AJT. In other words, we will develop methodologies that allow the inputs (the process parameters) to the surface evolution equation to be determined from a desired solution of the equation at some future time (the desired cross sectional profile). The problem is challenging because the surface evolution partial differential equation is nonlinear and cannot be solved in closed form. Initially, optimization routines will be used to determine the set of parameters that comes closest to a desired topography. Later, novel techniques for sculpting surfaces of desired shapes using combinations of inclined and perpendicular incidence nozzles will developed. These techniques will open up a host of new device design opportunities for the design of 3D MEMS and microfluidics devices, and thus support Canada's growing micro-technology sector.