Dynamics of liquid droplets in an evaporating drop: liquid droplet “coffee stain” effect
Bibliographic record
Abstract
In this paper, we demonstrate the dynamics of bidispersed oil droplets in an evaporating water sessile drop. This phenomenon is therefore equivalent to a unique liquid droplet based “coffee stain” effect, with the depositing colloidal particles (of a classical “coffee stain” problem) being replaced by the oil droplets partially wetting the substrate. The important difference with respect to the classical “coffee stain” problem, as revealed by our experiments, is that the oil droplets, unlike the colloidal particles, cannot reach the contact line; rather the aversion of the oil droplets to the air ensures that the oil droplets always remain at a finite distance from the contact line. We call this effect an “enclosure” effect, characterized by this distance. We provide a theoretical model to explain this phenomenon, and our theoretical results match well with the experimental observations. The “enclosure” effect depends on the droplet size, thereby allowing an automatic size-based separation of the oil droplets. Additionally, this effect depends on the wettability of the oil droplets and the sessile drop, as well as the relative velocity of the oil droplets with respect to the rate of decrease of the sessile drop contact angle. Our identification of this new phenomenon in a liquid-droplet based “coffee stain” problem will have a huge impact on microscale control and manipulation of liquid droplets in a two phase system.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".