Humidity-controlled direct ink writing for micro-additive manufacturing with water-based inks
Humidity-controlled direct ink writing for micro-additive manufacturing with water-based inks
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DOI：
10.1016/j.jmapro.2021.07.059
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发表时间：
2021-08-18
影响因子：
6.2
通讯作者：
Gozen, B. Arda
中科院分区：
文献类型：
--
作者：
Estelle, Kevin T.;Gozen, B. Arda
使用水基油墨（例如水凝胶或聚合物溶液）的直接油墨书写型增材制造被广泛用于生物打印应用。然而，由于在小尺寸尺度下经历的快速油墨干燥导致喷嘴堵塞和低保真度打印，该实施方式的分辨率是有限的。为了解决这个问题，提出了一种湿度控制的直接墨水书写（HCDIW）方法，其中通过引入雾化水来控制打印喷嘴周围的微环境。使用这种方法，喷嘴微环境可以在欠饱和但高相对湿度（环境至100%RH）到过饱和条件之间变化，在过饱和条件下，冷凝液滴沉积在已经打印的墨丝上。使用水溶性羧甲基纤维素钠（NaCMC）油墨研究了雾化水和所得微环境对印刷过程的影响，特别关注喷嘴堵塞、印刷长丝几何形状、表面质量和逐层堆叠。这些研究表明，油墨干燥引起的喷嘴堵塞问题可以通过增加喷嘴出口处的相对湿度来减轻，并且对于过饱和条件下的类似于100 μ m的喷嘴，几乎可以消除。在雾化水的作用下，油墨干燥速度减慢，导致溶质平流和表皮形成减少。这又改善了表面粗糙度，同时减少了在微尺度结构的增材制造期间的不利影响，例如咖啡环和空隙形成。此外，层与层的融合和相关的侧表面质量得到改善，特别是在欠饱和条件下。在过饱和条件下沉积的油墨丝浓度的降低导致沉积油墨的过度铺展，从而导致几何变形。这些结果表明，湿度控制方法可以显着提高直接墨水书写方法的分辨率，从而能够在微米尺度上处理水基墨水。
Direct-ink-writing type additive manufacturing with water-based inks such as hydrogels or polymer solutions is broadly utilized for bioprinting applications. However, the resolution of this implementation is limited due to the rapid ink drying experienced at small size scales leading to nozzle clogging and low fidelity prints. To address this issue, a humidity-controlled direct-ink-writing (HCDIW) approach is presented, where the microenvironment around the printing nozzle is controlled through introduction of aerosolized water. Using this approach, the nozzle microenvironment can be varied between undersaturated yet high relative humidity (ambient to 100% RH) to oversaturated conditions where condensing droplets are deposited on the already printed ink filaments. The influence of the aerosolized water and the resultant micro-environment on the printing process was studied using water dissolved sodium carboxymethyl cellulose (NaCMC) ink, specifically focusing on nozzle clogging, printed filament geometry, surface quality and layer by layer stacking. These studies showed that the ink drying induced nozzle clogging issues can be mitigated through increased relative humidity at the nozzle exit and is virtually eliminated for similar to 100 mu m nozzles in oversaturated conditions. The decelerated ink drying under the effect of aerosolized water leads to reduced solute advection and skin formation. This in turn improves surface roughness while reducing adverse effects such as coffee-ring and void formation during additive manufacturing of micro-scale structures. Furthermore, layer-to-layer fusion and associated side-surface quality were improved specifically in undersaturated conditions. Reduction of deposited ink filament concentration in oversaturated conditions leads to excessive spreading of the deposited inks leading to geometric distortions. These results indicate that the humidity control approach can significantly improve the resolution of the direct-ink-writing approaches, enabling processing of water-based inks at micro-scales.