(483g) Microswimmer Combing: A Dynamic and Ultra-Simple Approach for Rapid Isolation of Active Microswimmers on an Open Surface
To address this challenge, we develop an ultra-simple approach termed âmicroswimmer combingâ that can in parallel isolate highly active small animals from a suspension and individually address them on an open surface. Our approach exploits a novel dynamic sample loading mechanism by engineering local contact line dynamics on a 2D microgel array. The unique interfacial dynamics dominates the active locomotion of microswimmers, and hence achieves open-surface sample isolation. We demonstrate the efficacy of this approach using one of the most studied and hardest to isolate microswimmer, Caenorhabditis elegans, as a model. The open-surface substrate for housing individual C. elegans consists of an array of separated hydrophilic PEG-based microgel pads surrounded by a continuous, less-hydrophilic plastic surface made of structured Kapton tape. To capture individual microswimmers on the microgel array, we move a thin film of active worm suspension across the microgel array by a glass slide on top of the substrate, which we call âcombingâ. When the receding edge of the liquid film slides through, the imbalance of local capillary pressures between the microgel pad and the surrounding plastic surface due to their different wettabilities drives a rapid collapsing of opposite meniscus between two adjacent microgel pads. Such a fast contact line dynamic can hence pin the individual animal on a microgel pad autonomously. This approach can be performed simply by hand without any external equipment. More than 100 worms can be isolate on a single chip with 80% single isolation rate, within 30 seconds.
We provide a simple scaling theory to guide the design of the device for adapting this approach to different active bioparticles. The mechanistic principle underpins the robust sample loading which does not rely on user expertise; the isolation performance is largely guaranteed a priori by design. We demonstrate the effectiveness and simplicity of this approach by characterizing the consistent sample isolation performance with different device designs, loading conditions, and users. The open-surface array of isolated microswimmers can be directly used for multiple screening applications. Here we demonstrate the utility of this strategy with high-resolution image-based screening of synaptic development in larval C. elegans. Other screening functions, such as selective sample recovery, can also be enabled by the open-accessibility of individual samples isolated on our device. Although we demonstrate this method using nematode C. elegans as an example, we envision that our device, with proper scaling, can be easily modified to study other active microswimmer model systems, such as parasitic nematodes, D. rerio and Ciona larvae, and motile bacteria.
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