Pharmaceutical Analysis, Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, P.O. Box 196, 9700 AD Groningen, The Netherlands.
Lab Chip. 2016 Mar 21;16(6):1013-21. doi: 10.1039/c5lc01355k. Epub 2016 Feb 19.
We report on a new way to control solvent flows in paper microfluidic devices, based on the local patterning of paper with alkyl ketene dimer (AKD) to form barriers with selective permeability for different solvents. Production of the devices is a two-step process. In the first step, AKD-treated paper (hydrophobic) is exposed to oxygen plasma for re-hydrophilization. 3D-printed masks are employed to shield certain areas of this paper to preserve well-defined hydrophobic patterns. In the second step, concentrated AKD in hexane is selectively deposited onto already hydrophobic regions of the paper to locally increase the degree of hydrophobicity. Hydrophilic areas formed in the previous oxygen plasma step are protected from AKD by wetting them with water first to prevent the AKD hexane solution from entering them (hydrophilic exclusion). Characterization of the patterns after both steps shows that reproducible patterns are obtained with linear dependence on the dimensions of the 3D-printed masks. This two-step methodology leads to differential hydrophobicity on the paper: (i) hydrophilic regions, (ii) low-load AKD gates, and (iii) high-load AKD walls. The gates are impermeable to water, yet can be penetrated by most alcohol/water mixtures; the walls cannot. This concept for solvent-dependent on/off valving is demonstrated in two applications. In the first example, a device was developed for multi-step chemical reactions. Different compounds can be spotted separately (closed gates). Upon elution with an alcohol/water mixture, the gates become permeable and the contents are combined. In the second example, volume-defined sampling is introduced. Aqueous sample is allowed to wick into a device and fill a sample chamber. The contents of this sample chamber are eluted perpendicularly with an alcohol/water mixture through a selectively permeable gate. This system was tested with dye solution, and a linear dependence of magnitude of the signal on the sample chamber size was obtained.
我们报告了一种新的控制纸微流控装置中溶剂流动的方法，该方法基于局部对烷基烯酮二聚体 (AKD) 处理的纸张进行图案化，以形成对不同溶剂具有选择性渗透性的屏障。该装置的制作过程分为两步。在第一步中，AKD 处理过的纸张（疏水性）暴露于氧气等离子体中以重新亲水。使用 3D 打印掩模来屏蔽该纸张的某些区域，以保留明确定义的疏水性图案。在第二步中，将己烷中的浓缩 AKD 选择性地沉积到纸张的已经疏水的区域上，以局部增加疏水性程度。在先前的氧气等离子体步骤中形成的亲水区域通过首先用水润湿它们来防止 AKD 己烷溶液进入它们（亲水排斥）而免受 AKD 的影响。两步处理后对图案的表征表明，可以通过 3D 打印掩模的尺寸获得具有线性依赖性的可重复图案。这种两步方法导致纸张上的差异疏水性：（i）亲水区域，（ii）低负载 AKD 门，和（iii）高负载 AKD 壁。门对水是不可渗透的，但可以被大多数醇/水溶液渗透；墙壁不能。这种基于溶剂的开/关阀的概念在两个应用中得到了证明。在第一个例子中，开发了一种用于多步化学反应的装置。不同的化合物可以分别点样（关闭的门）。用醇/水溶液洗脱时，门变得可渗透，内容物被混合。在第二个例子中，引入了体积定义的采样。允许水性样品虹吸到装置中并填充样品室。通过选择性渗透的门，用醇/水溶液垂直地洗脱该样品室的内容物。该系统用染料溶液进行了测试，并获得了信号幅度与样品室尺寸的线性依赖性。
