Complex ink flow mechanisms in micro-direct-ink-writing and their implications on flow rate control
Complex ink flow mechanisms in micro-direct-ink-writing and their implications on flow rate control
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DOI：
10.1016/j.addma.2022.103183
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发表时间：
2022-10-07
影响因子：
11
通讯作者：
Gozen, B. Arda
中科院分区：
文献类型：
--
作者：
Estelle, Kevin T.;Gozen, B. Arda
尽管其简单，低成本和处理各种材料的能力，但直接油墨写入（DIW）是一种具有低分辨率和精度的增材制造工艺，在数百微米到毫米范围内。该问题的主要来源之一是在较小尺寸尺度下精确控制油墨流速的困难。为了解决这一限制，本文阐明了复杂的油墨流动机制，使流速控制困难，并探讨了印刷实现，以提高在微观尺度上的直接喷墨的流速精度。为此目的，采用混合压力和速度控制挤出的DIW系统，以获得水基羧甲基纤维素钠（NaCMC）溶液油墨的压力-流速关系，作为印刷喷嘴直径（510-100 μ m）的函数。这些研究表明，随着喷嘴直径的减小，活塞速度控制挤出的瞬态响应显著减慢。对于压力控制挤出，壁面滑移随着喷嘴直径的减小而增大，并且当喷嘴尺寸减小到一定直径以下时，恒定滑移速度假设不再成立。为了使这种行为对流速精度的影响情境化，对油墨进行温度控制的平行板流变测定，并相应地确定流变油墨模型。结果表明，由于缺乏壁面滑移的考虑，特别是对于较小的喷嘴尺寸，相关的流量预测低于预测流量。最后，一个迭代的压力控制DIW的实施进行了探讨，以解决微型DIW的精度问题。我们的研究结果表明，显着改善的瞬态响应和流量精度喷嘴直径小到100 μ m，使用这种方法相比，传统的压力和速度控制方法。
Despite its simplicity, low cost, and ability to process a wide range of materials, direct-ink-writing (DIW) is an additive manufacturing process with low resolution and accuracy, in the multiple hundred microns to millimeter range. One of the main sources for this issue is the difficulty with accurately controlling ink flow rate at smaller size scales. Towards addressing this limitation, this paper elucidates complex ink flow mechanisms that renders flow rate control difficult and explores printing implementations to increase flow rate accuracy in direct-inkwriting at the micro scale. To this end, a DIW system utilizing hybrid pressure and velocity-controlled extrusion is used to obtain pressure-flow rate relationships for a water-based sodium carboxymethyl cellulose (NaCMC) solution ink, as a function of printing nozzle diameter (510-100 mu m). These studies showed that the transient response of piston velocity-controlled extrusion significantly slows down with decreasing nozzle diameter. For pressure-controlled extrusion, the wall slip increases with decreasing nozzle diameter and the constant slip velocity assumption no longer holds as nozzle size decreases below a certain diameter. To contextualize the influence of such behavior on flow rate accuracy, temperature-controlled parallel plate rheometry was performed on the inks and rheological ink models were accordingly determined. It was shown that the associated flow rate predictions under predicted flow rates due to lack of wall-slip consideration, particularly for smaller nozzle sizes. Lastly, an iterative pressure-controlled DIW implementation was explored to address the accuracy issues for micro-DIW. Our results indicated significant improvement in the transient response and flow rate accuracy for nozzle diameters as small as 100 mu m using this approach compared to both of the conventional pressure and velocity control approaches.