这项研究得到了由教育部 (2016R1D1A1B01006801) 资助的韩国国家研究基金会 (NRF) 的基础科学研究项目的支持, 并得到了 Soonchunhyang 大学研究基金的部分支持。.

为了健康和安全起见, 在使用任何墨水和清洁解决方案之前, 请参阅材料安全数据表 (MSDS)。
1. 按需 Electrohydrodynamic 喷墨印花用银纳米粒子墨水
<ol><li>将经过过滤的银纳米微粒 (AgNP) 墨水填充在 EHD 印刷系统的墨水库中。 注: 市面上可用的 AgNP 墨水可用于喷墨用途。该油墨应具有约 10 cP 的粘度和表面张力为 20 ~ 40 锰/米, 以获得需求下降喷射。</li>
	<li>使用热拉拔器制作用于国防部 EHD 打印的喷嘴。<ol>
<li>将玻璃毛细管 [内径 (ID) 的1毫米] 放在热拉拔器中。</li>
		<li>设置热拉拔器的参数;例如, 加热温度的范围为 580-590 摄氏度, 拉动速度约为18毫米/秒。 注: 热拉拔的参数应根据目标喷嘴 ID 和环境条件而异。</li>
		<li>使用设定参数操作热拉拔器, 在毛细管的中心处加热, 并在两端拉起, 使喷嘴的 ID 为5µm。 注: 根据基板上的目标点大小确定喷嘴 ID 的大小。为参考, 5 µm 的喷嘴 ID 可以打印5个µm 大小的点。</li>
		<li>通过玻璃刀具切割玻璃喷嘴, 调整玻璃喷嘴的长度。</li>
	</ol>
</li>
	<li>将喷嘴装配到喷嘴架和连接器上,通过聚四氟乙烯 (PTFE) 油管连接到油墨储层。</li>
	<li>应用气压向喷嘴尖端提供墨水。<ol>
<li>打开气压控制器, 将 15 ~ 20 帕的气压用于墨水库, 以向喷嘴尖端提供墨水。通过透明的玻璃喷嘴和油管监测墨水的流动, 以确保在供应墨水时, 管子和喷嘴内没有空气被困住。继续将气压应用到墨水库, 直到墨水出现在喷嘴尖端。 注: 不要在喷嘴尖端出现墨水之前减少压力, 因为这可能会导致喷嘴尖端气泡的诱捕。</li>
		<li>减少压力到约12帕, 以保持挤压半月板没有任何墨水滴水从喷嘴尖端。 注: 适当的气压取决于喷嘴的大小和油墨的粘度。不要增加30帕的气压, 以避免过度的空气压缩, 这是不可取的保持在稳定的条件下半月板。</li>
	</ol>
</li>
	<li>将组装好的喷嘴头固定在打印系统中。</li>
	<li>将玻璃基板放在衬底架的真空吸盘上, 然后打开真空泵以保持基体。</li>
	<li>移动 Z 轴舞台以调整间隔距离 (H)-喷嘴尖端和衬底位置之间的间隙-到大约100µm. 使用监视摄像机获取的侧面视图图像来估计距离, 方法是使用从喷嘴尖端的反射, 如图 2所示。 注意: 一个较小的站距离导致一个更高的电场, 这可能有助于打印与较低的 DC 和脉冲电压喷射。然而, 较低的离站距离可能导致更大的水滴。因此, 应相应降低电压的大小以获得所需的点大小。一般情况下, 建议使用较低的电压, 以获得较小的印刷点, 喷涂较少。但是, 如果µm 距离小于 50, 则需要进行仔细的操作, 因为喷嘴破损的几率越高, 与基体碰撞就越大。考虑射流能力与可靠性之间的权衡关系, 建议使用100µm 的离站距离。</li>
</ol><img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57846/57846fig2.jpg"> 图 2: 使用侧面视图摄像机图像进行站距调整.从侧面摄像头的喷嘴图像可以用来估计的距离。从喷嘴尖端到基板的离站距离 (H) 可以很容易地估计为从喷嘴尖端到其阴影的一半距离。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<ol start="8"><li>
应用直流和脉冲电压 注: 直流和脉冲电压可通过打印软件进行控制。<ol>
<li>逐步增加直流电压, 直到墨水从喷嘴尖端流出。 注意: 不要同时应用目标电压。增量电压应小于 100 V 一次。整体上, 不要应用直流电压超过 600 v。</li>
		<li>将直流电压稍稍从起始直流电压中减小, 直到未观察到喷嘴的进一步滴墨。 注: 在气压和直流电压调整后, 半月板应在适当的形状中喷射, 如补充图 S1所示。</li>
		<li>设置一个负脉冲电压与参数的t上升= 0 ~ 100 µs, t驻留= 300 µs, 和t下降= 0 µs7 (图 3) 在软件菜单中。</li>
		<li>将负脉冲电压应用于衬底架上。然后, 调整脉冲电压的幅度, V脉冲, 产生一滴每单脉冲电压。 注: 负脉冲电压的大小, V脉冲, 应低于 600 v。</li>
		<li>调整 DC 背景和脉冲电压, 以获得在基板上的目标雾滴大小, 同时观察侧面相机图像中基板上的喷点。 注: 为了在承印物上产生较少喷涂的小点, 脉冲电压的幅度, V脉冲, 应尽可能低。</li>
	</ol>
</li>
</ol><img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57846/57846fig3.jpg"> 图 3: 国防部 EHD 喷射的脉冲电压.建议使用梯形波形电压来生产国防部 EHD 喷射7。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<ol start="9"><li>
打印图案 注: 两种不同的模式可用于国防部 EHD 打印: 位图图像和 (基于 CAD) 的矢量信息。位图图像已广泛应用于基于 DOD 的喷墨打印。然而, 在印刷电子应用的情况下, 基于 CAD 的矢量信息比基于 DOD 的喷墨打印具有优势, 因为它在基于线的打印中使用单一的 EHD 头是有效的。同时, 矢量信息可以转换为位图图像, 用于位图图像的打印。<ol>
<li>
位图图像打印
		<ol>
<li>在打印软件的 "打印" 选项卡中加载位图图像, 并将其转换为二进制图像。</li>
			<li>设置二进制图像打印的参数。例如, 将放置间隔 (即2 个连续像素之间的距离) 设置为10µm。 注意: 位图图像没有任何物理尺寸。打印图像的物理尺寸将与放置间隔相关。例如, 如果使用较大的放置间隔, 则打印的图像会变大。在传统的喷墨打印中, 每英寸点 (DPI) 通常用于这个目的。但是, 应该注意的是, 较小的 DPI 意味着更大的下降间隔。为了确定放置间隔, 应考虑打印点的大小。一般情况下, EHD 国防部印刷的下降间隔明显小于传统喷墨打印。</li>
			<li>使用所选位图在基板上的目标位置开始打印。</li>
		</ol>
</li>
		<li>
基于 CAD 信息的矢量打印
		<ol>
<li>加载 CAD 信息以进行打印。 注意: 文件格式 DXF 是基于文本的 CAD 信息, 可用于打印信息。</li>
			<li>设置矢量打印参数;例如, 将放置间隔设置为3µm, 在10赫兹处喷射频率。 注意: 要打印连接的线条图案, 应选择放置间隔, 以便相邻沉积滴略有重叠。但是, 过多的重叠可能会导致更大的线条宽度。对于任何实用的线打印, 建议重叠约30%。在矢量印刷的情况下, 运动速度 (v) 如下方程式。 v = d x f 这里 d = 放置间隔, 并 f = 喷射频率。</li>
			<li>使用预先确定的打印参数 (如放置间隔、打印速度、电压等) 打印基板上加载的图案. 注: 印刷后, 可能需要烧结过程, 以获得所需的导电性的印刷模式, 这是超出了本文的范围。</li>
		</ol>
</li>
	</ol>
</li>
</ol>2. 采用近场静电纺丝的精细导电线图案
<ol><li>为导电线印刷制作近场静电纺丝 (NFES) 油墨。<ol>
<li>将乙醇和去离子 (di) 水混合, 容积比为 3 (乙醇) 到 1 (di 水), 以制备溶剂1。例如, 混合9毫升乙醇和3毫升的 DI 水, 使12毫升溶剂1。</li>
		<li>将0.3 克的聚 (环氧乙烷) (乙烯基, M重量= 40万) 和9.7 克的制备溶剂 1, 通过搅拌, 在室温下使用磁力搅拌器超过3小时 (6 °c), 使聚合物溶液与 wt% 的25。</li>
		<li>混合银纳米糊墨, 其粘度约为 1.1万 cP, 并制备聚合物溶液, 其重量比为 5 (银纳米糊墨) 至 1 (聚合物溶液), 采用涡旋搅拌机10分钟获得油墨的 NFES.例如, 10 克的银纳米浆料油墨和2克聚合物溶液可以混合获得 NFES 油墨。 注: 在本协议中, 混合料的配比一般比材料的具体用量更重要。商业上可用的银纳米浆料油墨为丝网印刷目的, 具有 Ag 固体含量约 85.5 wt%, 可用于此目的。请注意, 溶剂和聚合物的选择可能根据所用墨水的成分而不同。</li>
	</ol>
</li>
	<li>在注射器中填充准备好的 NFES 墨水。</li>
	<li>通过连接管将注射器与喷嘴连接起来。 注: 可用于喷嘴的商用注射器针, 其 ID 为100µm。</li>
	<li>手动推注射器, 向喷嘴提供墨水。</li>
	<li>将注射器安装在注射器马达中, 连接到打印系统。</li>
	<li>在真空吸盘上放置基板, 在打印过程中打开真空泵以保持基体。</li>
	<li>控制 Z 位置 (舞台) 以调整离站距离。 注: 建议的离站距离应约2毫米, 这是一个显着较小的站距相比, 与传统的静电纺丝使用。</li>
	<li>
调整流量
	<ol>
<li>操作注射器泵, 以填充喷嘴组件中的 NFES 墨水, 并生成一个墨水流, 其初始流量为50µL/分钟, 高于目标流速。</li>
		<li>当墨水流出喷嘴尖端时, 设定目标流速为1µL/分钟。 注意: 较小的流量会导致图案宽度变小。然而, 它可能导致线断裂。在确定目标流速时, 应考虑线宽与直线延伸之间的权衡。</li>
	</ol>
</li>
	<li>
应用电压
	<ol>
<li>将直流电压源连接至喷嘴连接器, 并将接地电压连接到衬底架上。</li>
		<li>将直流电压逐步提高到1.5 伏。 注: 由于离站距离在几毫米范围内, 直流电压可提高2伏, 高于国防部 EHD 喷墨打印。然而, 应该避免直流电压高于2伏, 因为它可能会损坏功能材料, 特别是银糊墨水, 添加到聚合物溶液。一般来说, 当需要较薄的印制线时, 建议使用较低的直流电压。然而, 当使用低电压时, 印制线很容易断开, 因为连续油墨印刷的拉力与直流电压有关。考虑到权衡, 我们建议使用直流电压范围从1伏到2伏。</li>
	</ol>
</li>
	<li>以300毫米/秒的打印速度启动空闲打印, 以获得稳定状态的流。在空闲打印期间, 调整打印参数, 如直流电压和流量, 以获得所需的打印结果。 注: 由于粘性墨水在输送到喷嘴尖端时的长油管中可以被压缩, 因此需要10分钟以上的空闲打印才能获得稳态流量。如果不进行空闲打印, 打印线的宽度可能随时间而变化。因此, 怠速打印速度应与实际打印速度相同, 以便在打印过程中可以调整喷射参数。这样, 在空闲打印期间调整直流电压以获得目标线宽。请注意, 流量和直流电压应该是平衡的, 使注射器泵推的墨水量可以等于由电场拉下的墨水量。</li>
	<li>选择打印图案, 如连续线和网格图案。 注: 由于所生产的纤维容易偏转, 并且可以随机沉积, 因为印刷线产生的电荷排斥力, 印刷速度应大于300毫米/秒, 以使图案与印刷方向一致, 以及建议打印线间距大于100µm, 以打印网格或线条图案。</li>
	<li>使用预先确定的打印参数在基板上打印所选图案。 注: 可能需要烧结过程来获得印刷图案的目标功能, 这超出了本文的范围。</li>
</ol>

<ol>
	<li>Onses, M. S., Sutanto, E., Ferreira, P. M., Alleyne, A. G., Rogers, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms,+Capabilities,+and+Applications+of+High-Resolution+Electrohydrodynamic+Jet+Printing.">Mechanisms, Capabilities, and Applications of High-Resolution Electrohydrodynamic Jet Printing.</a> Small. 11 (34), 4237-4266 (2015).</li><li>Jaworek, A., Krupa, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Classification+of+the+modes+of+EHD+spraying.">Classification of the modes of EHD spraying.</a> Journal of Aerosol Science. 30 (93), 873-893 (1999).</li><li>Lee, A., Jin, H., Dang, H. W., Choi, K. H., Ahn, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+experimental+parameters+to+determine+the+jetting+regimes+in+electrohydrodynamic+printing.">Optimization of experimental parameters to determine the jetting regimes in electrohydrodynamic printing.</a> Langmuir. 29 (44), 13630-13639 (2013).</li><li>Sun, D., Chang, C., Li, S., Lin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Near-field+electrospinning.">Near-field electrospinning.</a> Nano Letters. 6 (4), 839-842 (2006).</li><li>Pan, C. -. T., Tsai, K. -. C., Wang, S. -. Y., Yen, C. -. K., Lin, Y. -. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-Area+Piezoelectric+PVDF+Fibers+Fabricated+by+Near-Field+Electrospinning+with+Multi-Spinneret+Structures.">Large-Area Piezoelectric PVDF Fibers Fabricated by Near-Field Electrospinning with Multi-Spinneret Structures.</a> Micromachines. 8 (4), (2017).</li><li>Mishra, S., Barton, K. L., Alleyne, A. G., Ferreira, P. M., Rogers, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-speed+and+drop-on-demand+printing+with+a+pulsed+electrohydrodynamic+jet.">High-speed and drop-on-demand printing with a pulsed electrohydrodynamic jet.</a> Journal of Micromechanics and Microengineering. 20 (9), (2010).</li><li>Kwon, K. S., Lee, D. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+pulse+voltage+shape+effects+on+electrohydrodynamic+jets+using+a+vision+measurement+technique.">Investigation of pulse voltage shape effects on electrohydrodynamic jets using a vision measurement technique.</a> Journal of Micromechanics and Microengineering. 23 (6), (2013).</li><li>Chen, C. H., Saville, D. A., Aksay, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaling+laws+for+pulsed+electrohydrodynamic+drop+formation.">Scaling laws for pulsed electrohydrodynamic drop formation.</a> Applied Physics Letters. 89, (2006).</li><li>Sung, K., Lee, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factors+influencing+liquid+breakup+in+electrohydrodynamic+atomization.">Factors influencing liquid breakup in electrohydrodynamic atomization.</a> Journal of Applied Physics. 96 (7), 3956-3961 (2004).</li><li>Kim, J. H., Oh, H. C., Kim, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrohydrodynamic+drop-on-demand+patterning+in+pulsed+cone-jet+mode+at+various+frequencies.">Electrohydrodynamic drop-on-demand patterning in pulsed cone-jet mode at various frequencies.</a> Journal of Aerosol Science. 39 (9), 819-825 (2007).</li><li>Phung, T. H., Kim, S., Kwon, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high+speed+electrohydrodynamic+(EHD)+jet+printing+method+for+line+printing.">A high speed electrohydrodynamic (EHD) jet printing method for line printing.</a> Journal of Micromechanics and Microengineering. 27, (2017).</li><li>Teo, W. E., Ramakrishna, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+electrospinning+design+and+nano+fiber+assemblies.">A review on electrospinning design and nano fiber assemblies.</a> Nanotechnology. 17, R89-R106 (2006).</li><li>Tang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+relective+nanofiber+films+based+on+electrospinning+and+their+application+on+color+uniformity+and+luminous+efficacy.">Highly relective nanofiber films based on electrospinning and their application on color uniformity and luminous efficacy.</a> Optics Express. 25, 20598-20611 (2017).</li><li>Huebner, G., Zapka, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+inkjet+with+other+printing+processes+and+mainly+screen+printing.">Comparing inkjet with other printing processes and mainly screen printing.</a> Handbook of Industrial Inkjet Printing - A Full System Approach. 1, 7-22 (2018).</li><li>Li, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+protein+fibers+as+matrices+for+tissue+engineering.">Electrospun protein fibers as matrices for tissue engineering.</a> Biomaterials. 26, 5999-6008 (2005).</li><li>Bhardwaj, N., Kundu, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning:+A+fascinating+fiber+fabrication+technique.">Electrospinning: A fascinating fiber fabrication technique.</a> Biotechnology Advances. 28, 325-347 (2010).</li><li>He, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Near-Field+Electrospinning:+Progress+and+Applications.">Near-Field Electrospinning: Progress and Applications.</a> The Journal of Physical Chemistry C. 121, 8663-8678 (2017).</li><li>Yang, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+fabrication+of+silver+nanowires+embedded+in+PVP+fibers+by+near-field+electrospinning+process.">Synthesis and fabrication of silver nanowires embedded in PVP fibers by near-field electrospinning process.</a> Optical Materials. 39, 118-124 (2015).</li><li>Chang, C., Limkrailassiri, K., Lin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+near-field+electrospinning+for+large+area+deposition+of+orderly+nanofiber+patterns.">Continuous near-field electrospinning for large area deposition of orderly nanofiber patterns.</a> Applied Physics Letters. 93 (12), (2008).</li></ol>

作者没有什么可透露的。

在本协议中, 我们将重点放在使用 AgNP 墨迹打印精细图案的两种模式: DOD EHD 打印和 NFES。然而, EHD 喷墨印花的应用并不局限于使用 AgNP 的导电油墨。在这里, 我们将讨论的一般准则, 选择的墨水, 系统配置, 和其他打印参数需要使用 EHD 喷墨打印的各种精细模式的应用。
EHD 印刷的第一个也是最重要的步骤是油墨的选择和准备。传统喷墨印花中使用的墨水可用于国防部 EHD 印刷。国防部喷墨打印油墨的粘度在 1 ~ 50 cp (通常 10 cp)14的范围内。然而, 应注意的是, 国防部 EHD 印刷的气动控制方法不同于传统的国防部喷墨打印机。传统的喷墨打印机使用负压保持喷嘴表面内的半月板位置, 以防止任何墨水滴水和喷嘴润湿。另一方面, EHD 国防部印刷使用正压, 这可以推动油墨形成一个挤出半月板。请注意, 如果油墨粘度超过 100 cP, 半月板是难以控制的, 因为空气可以很容易地压缩, 而不是把墨水推到喷嘴尖端。喷射的粘度范围取决于喷嘴的 ID。如果使用较小的喷嘴 ID, 则应相应地减少粘度, 以便在没有太多空气压缩的情况下向喷嘴尖端提供墨水。
油墨的表面张力对适当喷射也很重要。油墨的表面张力应在 20-40 锰/米的范围内。如果表面张力小于20锰/米, 喷涂效果将占主导地位。如果表面张力超过40锰/米, 就很难形成圆锥半月板, 这是适当的 EHD 喷射所需的。
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/57846/57846fig8.jpg"> 图 8: EHD 射流的表面张力效应.建议的油墨表面张力在 20-40 锰/米的范围内。如果表面张力变低, 对基体的喷涂效果将占主导地位。另一方面, 如果表面张力太高, 适当的 EHD 喷射是不可能的, 因为圆锥半月板是难以实现的。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig8large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
如果油墨的表面张力大于40锰/米, 可以将少量表面活性剂添加到油墨中, 以减少表面张力。然而, 过量表面活性剂的使用可能会导致承印物上的墨水喷洒。注意, 带电的墨水与某些极性可能产生排斥力在喷气飞行期间, 导致喷洒在基体上。为了降低喷涂效果, 可以考虑驱动电压或离站距离的降低。
可靠喷射的另一个重要参数是沸点。由于喷嘴的 ID 是非常小的情况下, EHD 射流, 挤压半月板, 由于正压, 可以很容易地干燥和堵塞喷嘴。为了减少喷嘴尖端的油墨干燥, 应根据其沸点高于150摄氏度的实际情况选择主要溶剂。为了防止由于粒子聚集而造成的堵塞, 请考虑用过滤器过滤墨水, 毛孔比喷嘴 ID 小。此外, 墨水中的粒子应该至少比喷嘴 ID 小10x。通常, 适用于传统压电喷墨打印机的油墨也可用于国防部 EHD 打印。
与国防部 EHD 喷墨墨水相比, NFES 油墨具有较高的粘度。粘度应在数千 cP 的范围内。对于连续印刷, 聚合物溶液与功能油墨混合。NFES 的应用最近从纤维生产15,16扩展到各种各样的应用通过混合功能材料与聚合物解答17。对于聚合物溶液, 聚氧乙烯和 PVP (polyvinylpyrrolidone)等4、5、17、18、19具有较高的分子量, 是常用的。与 NFES 的主要关注是保持连续印刷能力使用聚合物, 而油墨保持材料的功能, 如导电性。因此, 应仔细选择聚合物溶液与功能材料的混合比。此外, 与国防部的情况不同的是, 具有较低沸点 (小于100°c) 的溶剂通常用于制造聚合物溶液。
虽然传统喷墨墨水可用于国防部 EHD 印刷, EHD 印刷的压力控制方法不同于传统喷墨打印机。EHD 印刷使用正压, 以保持从喷嘴挤出半月板, 而传统的喷墨使用负压。对于正压控制, 两种类型的压力控制方法-水压和压力空气-可以使用, 取决于油墨黏度和喷嘴 ID, 如图 9所示。对于较小的喷嘴, 应使用气压而不是静水压来将墨水推到喷嘴尖端。但是, 如果使用高粘度墨水或带有 ID 少于2µm 的喷嘴, 空气压力的适当控制可能是困难的, 因为空气可以很容易地被压缩。另一方面, 如果喷嘴尺寸超过50µm, 轻微的气压变化会影响半月板的位置。如果油墨粘度低, 喷嘴超过50µm, 应使用射流高度的静水压压力来维持一个一致的半月板位置。
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/57846/57846fig9.jpg"> 图 9: 国防部喷射的压力控制.在待机状态下, 保持挤出半月板的正压力是必需的。半月板的压力可以由静水压压力 (使用墨层与喷嘴尖端之间的高度差) 或空气压缩机的压缩空气来控制。控制方法的选择应根据喷嘴大小和油墨粘度而异。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig9large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
在 NEFS 的情况下, 注射器泵可以用来向喷嘴输送墨水, 因为高粘性墨水不能被气压推。请注意, 墨水可以加压和压缩, 当它提供在恒定的流速通过注射器泵。此外, 压缩墨水可能需要相当长的时间才能到达喷嘴尖端的稳态流。为了尽量减少油墨压缩对印刷的影响, 插入注射器和喷嘴尖端之间的连接管应尽可能短。此外, 连接管应尽量减少压力粘性油墨引起的膨胀效应。为了尽量减少油墨的压缩效果, 应将注射器连接到印刷设备 (阶段), 以减少将注射器连接到喷嘴的管子的长度。为此, 我们使用了一个注射器泵, 其中螺杆马达可以与控制器分离, 如图 10所示。
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/57846/57846fig10.jpg"> 图 10: 用于静电纺丝的射流系统.静电纺丝射流系统由注射器泵系统和注射器喷嘴总成两部分组成。注射器泵系统包括流量控制器和螺杆马达。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig10large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
确定点尺寸或图案宽度的一个重要参数是喷嘴 ID。与传统的喷墨头不同, EHD 头不需要任何驱动器或复杂的流体通道。它只需要一个喷嘴, 如注射器针或玻璃毛细管喷嘴, 这是连接到一个高压源。在这种情况下, 应根据油墨黏度和花纹宽度选择合适的喷嘴内径大小。例如, 在国防部印刷使用低于 100 cP 的粘度时, 喷嘴 ID 应小于50µm。为了获得稳定和一致的印刷, 在待机状态下的挤出半月板应保持在同一位置。然而, 当使用 ID 大于50µm 的喷嘴时, 气压、驱动电压和站距距离的轻微变化很容易影响低粘性油墨的半月板位置。注意, 半月板位置与喷射量有关: 较低的位置通常会产生更多的水滴。因此, 当使用具有较大 ID 的喷嘴时, 在整个 DOD 打印过程中很难获得点均匀性。因此, 喷嘴 ID 应小于10µm, 以确保打印点尺寸均匀性。使用具有较小 ID 的喷嘴具有打印较小点的优点。例如, 带有3µm 的喷嘴 ID 可以打印小到3µm 的点, 并且可以通过使用较小 ID 的喷嘴进一步减少点大小。为了使喷嘴具有一个小的 ID, 通常使用玻璃毛细管, 因为具有目标 ID 的喷嘴可以很容易地通过商用热拉拔器制造。另一方面, NFES 需要一个大于50µm 的喷嘴 ID, 以打印高粘度 (大于 1000 cP) 墨水。通常, 具有100µm ID 的喷嘴通常用于精细图案印刷, 其图案宽度小于5µm。在这里, 一个商业上可用的注射器针可以用于这一目的。
在 DOD EHD 射流和 NFES 喷射中, 应考虑油墨黏度来选择喷嘴的 ID。此外, 射流系统中的压力 (或流速) 应根据喷嘴的 ID 和墨粘度来确定。图 11显示了三重要因素之间的关系: 油墨粘度、喷嘴尺寸和气压 (或流速)。如图 11所示, 使用高粘度墨水时应使用高压和具有大 id 的喷嘴, 而低气压和具有较小 id 的喷嘴则应用于喷射低粘性墨水。
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/57846/57846fig11.jpg"> 图 11: 关于粘度和压力的喷嘴选择指南.此图解释了喷嘴 ID、粘度和气压之间的关系。例如, 如果使用高粘性墨水, 则需要较大的喷嘴和/或更高的气压,反之亦然。同样, 对于半月板的控制, 需要更高的气压, 当使用一个较小的喷嘴, 或反之亦然。然而, 如果喷嘴的 ID 很小或粘度过高, 因为空气很容易被压缩, 高气压就不能把墨水适当地推到喷嘴尖端。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig11large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
在印刷过程中, 喷嘴的外部可能会被从喷嘴尖端流出的墨水所润湿。在存在明显的润湿性的情况下, 适当的喷射控制是困难的。可能造成润湿的原因可能是油墨性能不当, 例如表面张力, 或者是由于直流电压和压力/流量等参数设置不正确。如果喷嘴上的润湿仍然存在, 则可能需要喷嘴表面处理, 以便喷嘴表面对油墨具有疏水性特性。
对于国防部印刷, 需要两种不同类型的电压源7,11: 一个 DC 背景电压保持备用半月板形状, 和脉冲电压产生国防部喷射。然而, NFES 只使用直流电压打印连续的微线模式使用非常高粘性墨水 (超过 1000 cP)。高直流电压范围从1伏到2伏, 被应用到插在喷嘴和管之间的金属连接器上。为了打印一条直线, 我们使用了 1 ~ 3 mm 的短间隔距离, 这就是为什么这个方法被称为 "近场" 静电纺丝 (NFES), 它有不同的特点相比, 传统的远场静电纺丝12,13.
在该协议中, 用玻璃基板进行了实验, 但不同类型的基体可以根据应用。然而, 应该指出, 具有高绝缘性的基体 (例如, 聚乙烯对苯二甲酸乙二醇酯 (PET) 薄膜) 需要预处理, 如化学涂层, 以消除可能在表面积聚的静电电荷。
要使用 EHD 喷气机进行各种应用, 请在表 1中概述打印和准备指南。
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody>
<tr>
<td></td>
			<td>国防部 EHD 喷气印花</td>
			<td>近场静电纺丝 (连续印刷)</td>
		</tr>
<tr>
<td rowspan="3">油墨要求</td>
			<td>黏度范围: 1 ~ 100 cP。</td>
			<td>粘度: 100 cp ~ 1万 cp。</td>
		</tr>
<tr>
<td>表面张力: 20-40 锰/米。</td>
			<td rowspan="2">沸点: 小于100摄氏度。</td>
		</tr>
<tr>
<td>溶剂沸点: 150 摄氏度以上。</td>
		</tr>
<tr>
<td rowspan="2">射流系统</td>
			<td>流体高度 (静压力): 喷嘴内径大于50µm。</td>
			<td rowspan="2">具有恒定流速的注射器泵。</td>
		</tr>
<tr>
<td>气压: 喷嘴内径小于10µm。</td>
		</tr>
<tr>
<td rowspan="2">喷嘴内径要求</td>
			<td>不超过10µm 被推荐用于稳定喷射。</td>
			<td rowspan="2">超过100µm 可用于薄型图案, 宽度小于5µm。</td>
		</tr>
<tr>
<td>一般: 内径与5µm 可以打印约5µm 大小的点。</td>
		</tr>
<tr>
<td rowspan="2">电压要求</td>
			<td>直流背景电压: 小于 600 V</td>
			<td rowspan="2">直流电压: 小于2伏。</td>
		</tr>
<tr>
<td>喷射脉冲电压: 几上百伏。</td>
		</tr>
<tr>
<td>打印速度</td>
			<td>低, 小于10毫米/秒。</td>
			<td>速度超过300毫米/秒。</td>
		</tr>
<tr>
<td rowspan="2">软件要求</td>
			<td>光栅打印 (位图图像)。</td>
			<td>简单的网格模式。</td>
		</tr>
<tr>
<td>矢量打印 (基于 CAD 的信息)。</td>
			<td>由于射流的连续性质, 有无间断要求的模式是不可能的。</td>
		</tr>
</tbody></table>表 1: 国防部和连续 EHD 喷气机的制备和印刷指南摘要.该表总结了使用 EHD jet 进行精细模式的要求和建议。

EHD 喷墨印花已广泛应用于各种领域, 如印刷电子、生物技术和先进材料应用, 因为它能够高分辨率和低成本直接模式1。印制线宽度或印刷网点尺寸可降至1µm, 大大小于传统的压电式喷墨打印1。
在 EHD 印刷中, 一小部分墨水 (或半月板) 被推出喷嘴尖端, 并通过控制流速1、2、3、4、5或正气压1来维持. ,6,7。挤出半月板是充电, 可以很容易地从喷嘴尖端拉到基板的电场, 如图 1所示。锥形半月板在喷射过程中形成, 产生比喷嘴尺寸更薄的墨流。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57846/57846fig1.jpg"> 图 1: EHD 打印.图中显示了 EHD 喷墨打印的原理。墨水通过压力推挤并且通过电场拉扯从喷嘴形成一个被挤出的半月板。然后, 带电的墨水可以很容易地通过直流或脉冲电压喷射到基板。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
尽管单 EHD 打印机可用于两种不同的模式, 近场静电纺丝 (NFES) 和需求下降 (DOD) EHD 喷墨打印, 实现方法在油墨, 射流系统和驱动电压方面有显著差异1,2,3. 例如, NFES4、5使用相对高粘度的墨水 [超过 1000 centipoises (cP)] 形成连续的微线图案, 高速打印可达1米/秒。另一方面, 国防部 EHD 喷墨打印6,7,8使用低粘性墨水与粘度约 10 cP, 以打印点为基础的复杂模式, 低打印速度小于10毫米/秒。
由于对每种模式的要求都有很大的不同, 对缺乏经验的研究人员来说, 达到预期的结果可能会有挑战性。经验上的 "专门知识" 在实践中可能很重要。为了帮助研究人员习惯于印刷方法, 我们提出了用银纳米粒子墨水进行精细导电图案的 EHD 印刷协议。然而, 我们增加了对协议的评论, 使它们不限于使用银纳米粒子墨水的导电图案。最后, 讨论部分介绍了打印和准备指南。

<table border="0" cellpadding="0" cellspacing="0" width="696">
	<tbody>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">EHD integrated printing system</td>
			<td style="width:195px;">Psolution Ltd., South Korea</td>
			<td style="width:119px;">PS300</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Harima Ag Nanoparticle ink</td>
			<td style="width:195px;">Harima Inc., Japan</td>
			<td style="width:119px;">Harima NPS-JL</td>
			<td>Ag solid content: ~ 53 wt%, Viscosity: ~10 cP, Surface tension: ~30 mN/m</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Glass capillary</td>
			<td style="width:195px;">Narishige Scientific Instrument Lab</td>
			<td style="width:119px;">G-1</td>
			<td>Inner diameter: 1 mm; Used to make nozzle for DOD EHD jet printing using thermal puller</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Nozzle thermal puller</td>
			<td style="width:195px;">Sutter Instrument, USA</td>
			<td style="width:119px;">Sutter P-1000</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Microscope Slides (Glass subtrate)</td>
			<td style="width:195px;">Paul-Marienfeld &#38; Co.KG, Germany</td>
			<td style="width:119px;">10 006 12</td>
			<td>Dimension (L x W x T): 76 mm x 26 mm x 1 mm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Magnetic Stirrer</td>
			<td style="width:195px;">Barnstead Thermolyne Corp., USA</td>
			<td style="width:119px;">Cimarec SP131635</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Vortex Stirrer</td>
			<td style="width:195px;">Jeiotech, South Korea</td>
			<td style="width:119px;">Lab Companion VM-96T</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ag nanopaste&#160;</td>
			<td style="width:195px;">NPK, South Korea</td>
			<td style="width:119px;">ES-R001</td>
			<td>Ag solid content: ~85.5 wt%, Viscosity: ~11000 cP</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Poly ethylene oxide (PEO)</td>
			<td style="width:195px;">Sigma-Aldrich, USA</td>
			<td>372773-500G</td>
			<td>Mw = 400000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ethanol</td>
			<td style="width:195px;">Sigma-Aldrich, USA</td>
			<td>459836-500ML</td>
			<td></td>
		</tr>
	</tbody>
</table>

high-resolution patterning using two modes of electrohydrodynamic jet: drop on demand and near-field electrospinning

Electrohydrodynamic (EHD) 喷墨打印在各个领域引起了广泛的关注, 因为它可以作为一种高分辨率、低成本的直接图形工具。EHD 印刷使用射流供应商, 以保持挤出的半月板, 通过推动墨水出喷嘴尖端。然后用电场将半月板拉到基板上以产生高分辨率的图案。EHD 印刷的两种模式被用于精细模式: 连续近场静电纺丝 (NFES) 和基于点的需求下降 (DOD) EHD 印刷。根据印刷方式, 对印刷设备和油墨黏度的要求将有所不同。尽管采用单 EHD 打印机可以实现两种不同的模式, 但在油墨、射流系统和驱动电压方面, 实现方法有显著差异。因此, 如果不正确理解射流的要求和限制, 就很难取得预期的结果。本文的目的是提出一个指导方针, 使经验不足的研究人员可以减少试验和错误的努力, 使用 EHD 喷气机的具体研究和开发目的。为了演示精细模式的实现, 我们使用 Ag 纳米粒子墨水来实现协议中的导电模式。此外, 我们还提出了通用的印刷准则, 可用于其他类型的墨水为各种精细模式的应用。

基于点的按需打印: 国防部印刷是基于一滴喷射每一个喷射触发器。要生产国防部喷射, 应使用粘度约为 10 cP 的低粘性墨水。EHD 国防部印刷的墨水要求与传统的国防部喷墨打印机的需求相似, EHD 印刷方法与传统的国防部喷墨打印法是一样的。在传统的喷墨打印中, 光栅印刷技术被广泛应用, 因为它适用于使用多喷嘴头的位图图像打印。然而, 在 EHD 喷墨打印的情况下, 由于喷嘴之间的电交叉谈话, 多喷嘴头的实现有一个限制。因此, 使用单喷嘴的矢量打印通常用于基于 CAD 的线打印。尽管如此, 无论是光栅还是矢量打印模式都应该从打印软件中选择, 以打印各种类型的图案。注意, 算法和实现可以根据打印模式而有所不同。在矢量模式中, x、 y方向的同步移动用于打印线条, 而在光栅打印中, 单轴用于在主方向上打印点, 然后移动到子方向的下一条带状。图 4显示了使用光栅和矢量打印的代表性打印结果。
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57846/57846fig4.jpg"> 图 4: 使用 DOD EHD 喷射的典型打印结果.(a) 此面板显示位图打印 (光栅打印)。(b) 此面板显示基于 CAD 信息的矢量打印。基于点的 EHD jet 打印可用于同时打印位图图像 (光栅打印) 和基于 CAD 的线条 (矢量打印)。在这里, 250 伏的直流电压和-250 伏特的脉冲电压用于打印两种模式。在面板a中, 将放置间隔设置为10µm 以分隔点。在面板b中, 使用 10 Hz 的频率和3µm 的放置间隔打印图案, 以便将点连接到表格线。
近场静电纺丝: NFES 使用1000多个 cP 的高粘性墨水来连续打印图案。因此, 它不能打印位图图像, 也不能与打印和非打印位置的 CAD 信息。因此, NFES 不像复杂的图案, 而是使用高打印速度来打印直线。网格模式通常使用如图 5所示。
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57846/57846fig5.jpg"> 图 5: NFES 的典型打印结果.(a) 此面板显示了一种典型的静电纺丝印刷网格模式。(b) 此面板显示打印速度对打印结果的影响。NFES 要求高打印速度为两个目的: 减少图案宽度, 并使打印图案与打印方向对齐。由于在慢印区的喷射行为是不可预知的, 所以快速印刷区域应采用排除非直线零件的方法。
要使用 NFES 打印连续图案, 打印速度应快于300毫米/秒, 以将打印图案与打印方向对齐。快速打印速度也有助于实现一个薄的图案宽度11。与喷嘴 ID 相比, 图案宽度的降低比例可能超过 20x, 具体取决于打印条件。例如, 100 µm 的喷嘴 ID 可以产生小于5µm 的图案宽度。因此, NFES 是一个非常有效的方法, 以实现非常精细的模式使用高粘性墨水。然而, 图案的直线度和宽度很容易受到印刷速度的变化。请注意, 有不可避免的加速和减速区域, 打印速度可能变得非常低 (或零), 以改变印刷方向。在这些地区, 印刷图案可能变得不均匀, 不符合移动方向。因此, 我们建议只在高速区域附近使用印刷图案。应丢弃靠近加速度和减速区域 (低打印速度区域) 的打印模式, 如图 5a所示。在某些情况下, 低喷射速度可以用来产生波浪模式。通过使用小于100毫米/秒的低打印速度, 图案可以变成波浪形, 如图 6所示。波形图案可能在可伸缩电子应用中很有用。但是, 由于打印速度低, 线宽可增加10µm。
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/57846/57846fig6.jpg"> 图 6: 使用低打印速度的波形图案示例.低打印速度 (约100毫米/秒) 可产生波形线。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig6large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
在某些印刷应用中, 需要非常精细的图案, 宽度小于1µm。为了达到如此精细的图案, 可以考虑打印速度快于1米/秒。但是, 过高的打印速度可能导致断开 (或断开) 线路。因此, 需要对聚合物的流量、线宽、印刷速度、拉伸等各种印刷条件进行优化, 以打印出没有任何线破损的精细图案。例如,图 7显示了打印速度和直流电压分别为300毫米/秒和 1200 V 时, 打印结果的流量影响。
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/57846/57846fig7.jpg"> 图 7: 按流速的图案宽度.流量与花纹宽度有关。随着流速的降低, 可以得到更精细的模式。例如, 如果流量高, 50 µL/分钟, 线宽将大与34µm。当流量降低到1µL/分钟和0.1 µL/分钟时, 可以得到更精细的模式, 宽度为8µm 和1µm。请注意, 如果流量太小, 线路模式可以断开和断开连接。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/57846fig7large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
图 S1: 根据打印条件, 备用半月板形状.在整个印刷过程中, 应保持适当的气压和直流背景电压, 以获得稳定的 DOD 喷射, 以保证合适的半月板形状。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/Figure_S1.tif">请单击此处下载此文件.</a>
图 S2: 静电纺丝印刷示意图.介绍了静电纺丝印刷的部件。请注意, 高直流电压被应用到喷嘴架上, 向墨水提供电荷, 并产生将墨水拉到基体上的电场。在 NFES 的情况下, 从喷嘴尖端到衬底的距离应为直线印刷沿印刷方向的 1 ~ 3 毫米。<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57846/Figure_S2_Modified.tif">请单击此处下载此文件.</a>

Watch this Scientific Journal Video about High-resolution Patterning Using Two Modes of Electrohydrodynamic Jet: Drop on Demand and Near-field Electrospinning at JoVE.com

High-resolution Patterning Using Two Modes of Electrohydrodynamic Jet: Drop on Demand and Near-field Electrospinning

采用两种 Electrohydrodynamic 射流的高分辨率模式: 需求下降和近场静电纺丝

在这里, 我们提出了一个协议, 以产生高分辨率导电模式使用 electrohydrodynamic (EHD) 喷墨打印。该协议包括两种 EHD 喷墨打印模式: 连续近场静电纺丝 (NFES) 和基于点的需求下降 (DOD) EHD 打印。

Electrohydrodynamic (EHD) jet printing has drawn attention in various fields because it can be used as a high-resolution and low-cost direct patterning ...

high-resolution-patterning-using-two-modes-electrohydrodynamic-jet

Nanyang Technological University

Research

JoVE Journal

Bioengineering

9.6K 次观看.  Soonchunhyang University. 在这里, 我们提出了一个协议, 以产生高分辨率导电模式使用 electrohydrodynamic (EHD) 喷墨打印。该协议包括两种 EHD 喷墨打印模式: 连续近场静电纺丝 (NFES) 和基于点的需求下降 (DOD) EHD 打印。

视频: High-resolution Patterning Using Two Modes of Electrohydrodynamic Jet: Drop on Demand and Near-field Electrospinning

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution. Traditionally, multiple experiments are run in parallel, with individual samples removed from the study at sequential time points for evaluation by light microscopy. Several intravital techniques have been developed, with confocal, multiphoton, and second harmonic microscopy all demonstrating their ability to be used for imaging in situ 1. With these systems, however, the required infrastructure is complex and expensive, involving scanning laser systems and complex light sources. Here we present a protocol for the design and assembly of a high-resolution microendoscope which can be built in a day using off-the-shelf components for under US$5,000. The platform offers flexibility in terms of image resolution, field-of-view, and operating wavelength, and we describe how these parameters can be easily modified to meet the specific needs of the end user.
We and others have explored the use of the high-resolution microendoscope (HRME) in in vitro cell culture 2-5, in excised 6 and living animal tissues 2,5, and in human tissues in vivo 2,7. Users have reported the use of several different fluorescent contrast agents, including proflavine 2-4, benzoporphyrin-derivative monoacid ring A (BPD-MA) 5, and fluoroscein 6,7, all of which have received full, or investigational approval from the FDA for use in human subjects. High-resolution microendoscopy, in the form described here, may appeal to a wide range of researchers working in the basic and clinical sciences. The technique offers an effective and economical approach which complements traditional benchtop microscopy, by enabling the user to perform high-resolution, longitudinal imaging in situ.

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

In many biological and clinical situations it is advantageous to study cellular processes as they evolve in their native microenvironment. Here we describe the assembly and use of a low-cost fiber-optic microscope which can provide real time imaging in cell culture, animal studies, and clinical patient studies.

高分辨率光纤内窥镜为原位细胞成像

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution.  ...

科研

生物工程

Electrospinning Fundamentals: Optimizing Solution and Apparatus Parameters

Electrospun nanofiber scaffolds have been shown to accelerate the maturation, improve the growth, and direct the migration of cells in vitro. Electrospinning is a process in which a charged polymer jet is collected on a grounded collector; a rapidly rotating collector results in aligned nanofibers while stationary collectors result in randomly oriented fiber mats. The polymer jet is formed when an applied electrostatic charge overcomes the surface tension of the solution. There is a minimum concentration for a given polymer, termed the critical entanglement concentration, below which a stable jet cannot be achieved and no nanofibers will form - although nanoparticles may be achieved (electrospray). A stable jet has two domains, a streaming segment and a whipping segment. While the whipping jet is usually invisible to the naked eye, the streaming segment is often visible under appropriate lighting conditions. Observing the length, thickness, consistency and movement of the stream is useful to predict the alignment and morphology of the nanofibers being formed. A short, non-uniform, inconsistent, and/or oscillating stream is indicative of a variety of problems, including poor fiber alignment, beading, splattering, and curlicue or wavy patterns. The stream can be optimized by adjusting the composition of the solution and the configuration of the electrospinning apparatus, thus optimizing the alignment and morphology of the fibers being produced. In this protocol, we present a procedure for setting up a basic electrospinning apparatus, empirically approximating the critical entanglement concentration of a polymer solution and optimizing the electrospinning process. In addition, we discuss some common problems and troubleshooting techniques.

Electrospinning techniques can create a variety of nanofibrous scaffolds for tissue engineering or other applications. We describe here a procedure to optimize the parameters of the electrospinning solution and apparatus to obtain fibers with the desired morphology and alignment. Common problems and troubleshooting techniques are also presented.

静电基础:优化解决方案和设备参数

Electrospun nanofiber scaffolds have been shown to accelerate the maturation, improve the growth, and direct the migration of cells in vitro. ...

Visualization of Cortex Organization and Dynamics in Microorganisms, using Total Internal Reflection Fluorescence Microscopy

TIRF microscopy has emerged as a powerful imaging technology to study spatio-temporal dynamics of fluorescent molecules in vitro and in living cells1. The optical phenomenon of total internal reflection occurs when light passes from a medium with high refractive index into a medium with low refractive index at an angle larger than a characteristic critical angle (i.e. closer to being parallel with the boundary). Although all light is reflected back under such conditions, an evanescent wave is created that propagates across and along the boundary, which decays exponentially with distance, and only penetrates sample areas that are 100-200 nm near the interface2. In addition to providing superior axial resolution, the reduced excitation of out of focus fluorophores creates a very high signal to noise ratios and minimizes damaging effects of photobleaching2,3. Being a widefield technique, TIRF also allows faster image acquisition than most scanning based confocal setups.
At first glance, the low penetration depth of TIRF seems to be incompatible with imaging of bacterial and fungal cells, which are often surrounded by thick cell walls. On the contrary, we have found that the cell walls of yeast and bacterial cells actually improve the usability of TIRF and increase the range of observable structures4-8. Many cellular processes can therefore be directly accessed by TIRF in small, single-cell microorganisms, which often offer powerful genetic manipulation techniques. This allows us to perform in vivo biochemistry experiments, where kinetics of protein interactions and activities can be directly assessed in living cells.
We describe here the individual steps required to obtain high quality TIRF images for Saccharomyces cerevisiae or Bacillus subtilis cells. We point out various problems that can affect TIRF visualization of fluorescent probes in cells and illustrate the procedure with several application examples. Finally, we demonstrate how TIRF images can be further improved using established image restoration techniques.

Total Internal Reflection Fluorescence (TIRF) microscopy is a powerful approach to observe structures close to the cell surface at high contrast and temporal resolution. We demonstrate how TIRF can be employed to study protein dynamics at the cortex of cell wall-enclosed bacterial and fungal cells.

皮层组织和动态可视化的微生物，利用全内反射荧光显微镜

TIRF microscopy has emerged as  a powerful imaging technology to study spatio-temporal dynamics of fluorescent molecules  in vitro and in living cells1. ...

Cell Co-culture Patterning Using Aqueous Two-phase Systems

Cell patterning technologies that are fast, easy to use and affordable will be required for the future development of high throughput cell assays, platforms for studying cell-cell interactions and tissue engineered systems. This detailed protocol describes a method for generating co-cultures of cells using biocompatible solutions of dextran (DEX) and polyethylene glycol (PEG) that phase-separate when combined above threshold concentrations. Cells can be patterned in a variety of configurations using this method. Cell exclusion patterning can be performed by printing droplets of DEX on a substrate and covering them with a solution of PEG containing cells. The interfacial tension formed between the two polymer solutions causes cells to fall around the outside of the DEX droplet and form a circular clearing that can be used for migration assays. Cell islands can be patterned by dispensing a cell-rich DEX phase into a PEG solution or by covering the DEX droplet with a solution of PEG. Co-cultures can be formed directly by combining cell exclusion with DEX island patterning. These methods are compatible with a variety of liquid handling approaches, including manual micropipetting, and can be used with virtually any adherent cell type.

Aqueous two-phase systems were used to simultaneously pattern multiple populations of cells. This fast and easy method for cell patterning takes advantage of the phase separation of aqueous solutions of dextran and polyethylene glycol and the interfacial tension that exists between the two polymer solutions.

利用双水相系统的细胞共培养图案

Cell patterning  technologies that are fast, easy to use and affordable will be required for the  future development of high throughput cell assays, ...

Permeabilization of Adhered Cells Using an Inert Gas Jet

Various cell transfection techniques exist and these can be broken down to three broad categories: viral, chemical and mechanical. This protocol describes a mechanical method to temporally permeabilize adherent cells using an inert gas jet that can facilitate the transfer of normally non-permeable macromolecules into cells. We believe this technique works by imparting shear forces on the plasma membrane of adherent cells, resulting in the temporary formation of micropores. Once these pores are created, the cells are then permeable to genetic material and other biomolecules. The mechanical forces involved do run the risk of permanently damaging or detaching cells from their substrate. There is, therefore, a narrow range of inert gas dynamics where the technique is effective. An inert gas jet has proven efficient at permeabilizing various adherent cell lines including HeLa, HEK293 and human abdominal aortic endothelial cells. This protocol is appropriate for the permeabilization of adherent cells both in vitro and, as we have demonstrated, in vivo, showing it may be used for research and potentially in future clinical applications. It also has the advantage of permeabilizing cells in a spatially restrictive manner, which could prove to be a valuable research tool.

This protocol describes a method for the temporary permeabilization of adherent cells using an inert gas jet. This technique facilitates the transfer of genetic material and biomolecules into adherent mammalian cells by the utilization of mechanical forces to disrupt the plasma membrane.

粘附细胞用惰性气体喷射的透

Various cell transfection techniques exist and these can be broken down to three broad categories: viral, chemical and mechanical. This protocol describes ...

Cell Patterning on Photolithographically Defined 
Parylene-C: SiO2 Substrates

Cell patterning platforms support broad research goals, such as construction of predefined in vitro neuronal networks and the exploration of certain central aspects of cellular physiology. To easily combine cell patterning with Multi-Electrode Arrays (MEAs) and silicon-based &#8216;lab on a chip&#8217; technologies, a microfabrication-compatible protocol is required. We describe a method that utilizes deposition of the polymer parylene-C on SiO2&#160;wafers. Photolithography enables accurate and reliable patterning of parylene-C at micron-level resolution. Subsequent activation by immersion in fetal bovine serum (or another specific activation solution) results in a substrate in which cultured cells adhere to, or are repulsed by, parylene or SiO2 regions respectively. This technique has allowed patterning of a broad range of cell types (including primary murine hippocampal cells, HEK 293 cell line, human neuron-like teratocarcinoma cell line, primary murine cerebellar granule cells, and primary human glioma-derived stem-like cells). Interestingly, however, the platform is not universal; reflecting the importance of cell-specific adhesion molecules. This cell patterning process is cost effective, reliable, and importantly can be incorporated into standard microfabrication (chip manufacturing) protocols, paving the way for integration of microelectronic technology.

Cell Patterning on Photolithographically Defined 
Parylene-C: SiO2 Substrates

This protocol describes a microfabrication-compatible method for cell patterning on SiO2. A predefined parylene-C design is photolithographically printed on SiO2 wafers. Following incubation with serum (or other activation solution) cells adhere specifically to (and grow according to the conformity of) underlying parylene-C, whilst being repulsed by SiO2 regions.

在光刻技术定义的聚对二甲苯-C细胞图案:二氧化硅<sub&gt; 2</sub&gt;基板

Cell patterning platforms support broad research goals, such as construction of predefined in vitro neuronal networks and the exploration of certain ...

Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol adhesive through a metal stencil, the overall amount of adhesive used in assembling paper microfluidic devices can be significantly reduced. We show on a simple 4-layer planar paper microfluidic device that the optimal adhesive application technique and device construction style depends heavily on desired performance characteristics. By moderately increasing the overall area of a device, it is possible to dramatically decrease the wicking time and increase device success rates while also reducing the amount of adhesive required to keep the device together. Such adhesive application also causes the adhesive to form semi-permanent bonds instead of permanent bonds between paper layers, enabling single-use devices to be non-destructively disassembled after use. Nonplanar 3D origami devices also benefit from the semi-permanent bonds during folding, as it reduces the likelihood that unrelated faces may accidently stick together. Like planar devices, nonplanar structures see reduced wicking times with patterned adhesive application vs uniformly applied adhesive.

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

使用粘性图案构建3D纸微流体装置

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol ...

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Protocols are described for the fabrication of degradable thermoresponsive hydrogels based on hydrazone cross-linking of polymeric oligomers on the bulk scale, microscale, and nanoscale, the latter for preparation of both gel nanoparticles and nanofibers.

通过反应挤出、微流体、自组装和电纺丝制备多长尺度可降解 Thermoresponsive 水凝胶

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), ...

Patterning Bioactive Proteins or Peptides on Hydrogel Using Photochemistry for Biological Applications

There are many biological stimuli that can influence cell behavior and stem cell differentiation. General cell culture approaches rely on soluble factors within the medium to control cell behavior. However, soluble additions cannot mimic certain signaling motifs, such as matrix-bound growth factors, cell-cell signaling, and spatial biochemical cues, which are common influences on cells. Furthermore, biophysical properties of the matrix, such as substrate stiffness, play important roles in cell fate, which is not easily manipulated using conventional cell culturing practices. In this method, we describe a straightforward protocol to provide patterned bioactive proteins on synthetic polyethylene glycol (PEG) hydrogels using photochemistry. This platform allows for the independent control of substrate stiffness and spatial biochemical cues. These hydrogels can achieve a large range of physiologically relevant stiffness values. Additionally, the surfaces of these hydrogels can be photopatterned with bioactive peptides or proteins via thiol-ene click chemistry reactions. These methods have been optimized to retain protein function after surface immobilization. This is a versatile protocol that can be applied to any protein or peptide of interest to create a variety of patterns. Finally, cells seeded onto the surfaces of these bioactive hydrogels can be monitored over time as they respond to spatially specific signals.

In this method, we use photopolymerization and click chemistry techniques to create protein or peptide patterns on the surface of polyethylene glycol (PEG) hydrogels, providing immobilized bioactive signals for the study of cellular responses in vitro.

生物活性蛋白或多肽在水凝胶上的应用

There are many biological stimuli that can influence cell behavior and stem cell differentiation. General cell culture approaches rely on soluble factors ...

Quantifying Microorganisms at Low Concentrations Using Digital Holographic Microscopy (DHM)

Accurately detecting and counting sparse bacterial samples has many applications in the food, beverage, and pharmaceutical processing industries, in medical diagnostics, and for life detection by robotic missions to other planets and moons of the solar system. Currently, sparse bacterial samples are counted by culture plating or epifluorescence microscopy. Culture plates require long incubation times (days to weeks), and epifluorescence microscopy requires extensive staining and concentration of the sample. Here, we demonstrate how to use off-axis digital holographic microscopy (DHM) to enumerate bacteria in very dilute cultures (100-104 cells/mL). First, the construction of the custom DHM is discussed, along with detailed instructions on building a low-cost instrument. The principles of holography are discussed, and a statistical model is used to estimate how long videos should be to detect cells, based on the optical performance characteristics of the instrument and the concentration of the bacterial solution (Table 2). Video detection of cells at 105, 104, 103, and 100 cells/mL is demonstrated in real time using un-reconstructed holograms. Reconstruction of amplitude and phase images is demonstrated using an open-source software package.

Quantifying Microorganisms at Low Concentrations Using Digital Holographic Microscopy DHM

Digital holographic microscopy (DHM) is a volumetric technique that allows imaging samples 50-100X thicker than brightfield microscopy at comparable resolution, with focusing performed post-processing. Here DHM is used for identifying, counting, and tracking microorganisms at very low densities and compared with optical density measurements, plate count, and direct count.

用数字全息显微镜 (DHM) 定量化低浓度微生物

Accurately detecting and counting sparse bacterial samples has many applications in the food, beverage, and pharmaceutical processing industries, in ...