Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India.
Department of Cell Biology and Microbiology, Indian Institute of Science, Bangalore 560012, India.
J Colloid Interface Sci. 2022 Jan 15;606(Pt 2):2011-2023. doi: 10.1016/j.jcis.2021.09.158. Epub 2021 Oct 6.
Deposits of biofluid droplets on surfaces (such as respiratory droplets formed during an expiratory) are composed of water-based salt-protein solution that may also contain an infection (bacterial/viral). The final patterns of the deposit formed and bacterial aggregation on the deposits are dictated by the fluid composition and flow dynamics within the droplet.
This work reports the spatio-temporal, topological regulation of deposits of respiratory fluid droplets and control of bacterial aggregation by tweaking flow inside droplets using non-contact vapor-mediated interactions. Desiccated respiratory droplets form deposits with haphazard multiscale dendritic, cruciform-shaped precipitates when evaporated on a glass substrate. However, we showcase that short and long-range vapor-mediated interaction between the droplets can be used as a tool to control these deposits at nano-micro-millimeter scales. We morphologically control hierarchial dendrite size, orientation and subsequently suppress cruciform-shaped crystals by placing a droplet of ethanol in the vicinity of the biofluid droplet. Active living matter in respiratory fluids like bacteria is preferentially segregated and agglomerated without its viability and pathogenesis attenuation.
The nucleation sites can be controlled via preferential transfer of solutes in the droplets; thus, achieving control over crystal occurrence, growth dynamics, and the final topology of the deposit. For the first time, we have experimentally presented a proof-of-concept to control the aggregation of live active matter like bacteria without any direct contact. The methodology can have ramifications in biomedical applications like disease detection and bacterial segregation.
液滴（如呼气过程中形成的呼吸液滴）表面上的生物流体液滴沉积物由基于水的盐-蛋白质溶液组成，该溶液可能还含有感染（细菌/病毒）。沉积物形成的最终图案和沉积物上细菌的聚集是由液滴内的流体成分和流动动力学决定的。
这项工作报道了呼吸液滴沉积物的时空、拓扑调控以及通过使用非接触蒸气介导相互作用来调整液滴内的流动来控制细菌聚集。干燥的呼吸液滴在玻璃基底上蒸发时会形成具有随意多尺度树枝状、十字形沉淀物的沉积物。然而，我们展示了可以将短程和长程蒸气介导相互作用用作工具，以在纳米-微米-毫米尺度上控制这些沉积物。我们通过在生物流体液滴附近放置一滴乙醇来控制分级树枝状结构的大小、方向，从而抑制十字形晶体的形成。呼吸道液中的活的生物物质（如细菌）被优先分离和聚集，而不会降低其生存能力和发病机制。
可以通过优先转移液滴中的溶质来控制成核点；从而实现对晶体出现、生长动力学和沉积物最终拓扑结构的控制。我们首次通过实验提出了一个概念验证，即在不进行任何直接接触的情况下控制活的活性物质（如细菌）的聚集。该方法可能在疾病检测和细菌分离等生物医学应用中产生影响。
