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

多年来，由空气或水推动的细小磨粒射流一直被用于改变工程表面的表面形貌。磨料喷射技术(AJT)最重要的应用之一是作为微流体、微电子机械系统(MEMS)和光电子元件的低成本快速微细加工平台。本文将重点研究两种AJT技术：气动磨料射流微加工(AJM)和磨料水射流微加工(AWJM)。这些技术的优势有很多，但也许最重要的是，它们可以在不产生热影响区域的情况下进行加工，并且它们具有大多数竞争技术所不具备的独特的定向蚀刻能力。例如，传统的各向同性湿法刻蚀沟道会产生单个基本的U形微沟道横截面。然而，AJT的定向蚀刻能力允许通过改变工艺参数(例如，喷射扫描速度和倾角、颗粒大小等)来雕刻许多不同的形状。拟议中的研究将利用这一独特的能力，使这项技术能够用于制造新的设备。**我们以前为各种材料的AJM开发了“表面演变”模型，该模型可以预测在各种工艺参数组合下最初平坦表面上的机械加工地形的发展。然而，下一代微流控和MEMS设备将需要微加工3D(即非平面)组件，尽管AJM具有巨大的潜力，但这一领域尚未被探索。同样，目前还没有表面演变模型来预测AWJM的加工表面形貌，AWJM是一种较新的工艺，由于磨料浆回流效应和没有掩膜，它与AJM有根本的不同。通过与一家工业合作伙伴的独家协议，我们拥有一台带有独特微喷嘴的AWJM设备，这将使我们能够在这一领域进行开创性的研究。AJT的一个复杂因素是颗粒嵌入表面的倾向，从而影响表面质量、侵蚀速度、粗糙度等。目前，在使用AJT加工金属时，没有模型可以预测哪些颗粒和工艺参数控制这种嵌入的程度。拟议研究的初始部分将侧重于解决AJT过程建模中的这些重要缺陷。**表面演变模型很重要，因为它们可以预测作为输入工艺参数的函数的加工地形；然而，目前还没有解决反问题的技术，即预测雕刻特定所需地形所需的工艺参数。拟议研究的最后部分将解决这一重要问题，即允许使用AJT来雕刻特定的所需特征形状。换句话说，我们将开发一种方法，允许在未来某个时间(期望的横截面轮廓)根据方程的期望解来确定表面演化方程的输入(过程参数)。这是一个具有挑战性的问题，因为表面演化偏微分方程是非线性的，不能用闭合形式求解。最初，将使用优化例程来确定最接近所需地形的参数集。稍后，将开发使用倾斜和垂直入射喷嘴的组合来雕刻所需形状的表面的新技术。这些技术将为3DMEMS和微流体设备的设计打开大量新的设备设计机会，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.