Department of Chemical Engineering, Loughborough University, LoughboroughLE11 3TU, United Kingdom.
Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, LoughboroughLE11 3TU, United Kingdom.
Langmuir. 2022 Nov 22;38(46):14053-14062. doi: 10.1021/acs.langmuir.2c01755. Epub 2022 Nov 9.
The delivery of colloidal particles in dead-end microstructures is very challenging, since these geometries do not allow net flows of particle-laden fluids; meanwhile, diffusive transport is slow and inefficient. Recently, we introduced a novel particle manipulation strategy, based on diffusiophoresis, whereby the salt concentration gradient between parallel electrolyte streams in a microgrooved channel induces the rapid (i.e., within minutes) and reversible accumulation, retention, and removal of colloidal particles in the microgrooves. In this study, we investigated the effects of salt contrast and groove depth on the accumulation process in silicon microgrooves and determined the experimental conditions that lead to a particle concentration peak of more than four times the concentration in the channel bulk. Also, we achieved an average particle concentration in the grooves of more than twice the concentration in the flowing streams and almost 2 orders of magnitude larger than the average concentration in the grooves in the absence of a salt concentration gradient. Analytical sufficient and necessary conditions for particle accumulation are also derived. Finally, we successfully tested the accumulation process in polydimethylsiloxane microgrooved channels, as they are less expensive to fabricate than silicon microgrooved substrates. The controlled and enhanced accumulation of colloidal particles in dead-end structures by solute concentration gradients has potential applications in soft matter and living systems, such as drug delivery, synthetic biology, and on-chip diagnostics.
在死端微结构中输送胶体颗粒非常具有挑战性，因为这些几何形状不允许载有颗粒的流体进行净流动；同时，扩散传输缓慢且效率低下。最近，我们引入了一种基于扩散泳的新型粒子操纵策略，在微槽道中的平行电解质流之间的盐浓度梯度会导致胶体颗粒在微槽道中快速（即在几分钟内）且可逆地积累、保留和去除。在这项研究中，我们研究了盐对比和槽深对硅微槽道中积累过程的影响，并确定了导致颗粒浓度峰值超过通道主体浓度四倍以上的实验条件。此外，我们还实现了槽中颗粒的平均浓度超过流动流中浓度的两倍，并且比没有盐浓度梯度时槽中颗粒的平均浓度大近两个数量级。还推导出了颗粒积累的充分和必要的解析条件。最后，我们成功地在聚二甲基硅氧烷微槽道中测试了积累过程，因为它们的制造成本比硅微槽道衬底低。通过溶质浓度梯度在死端结构中对胶体颗粒进行可控且增强的积累在软物质和生命系统中具有潜在的应用，例如药物输送、合成生物学和片上诊断。
