Spontaneous rolling of a soft sphere on a vertical soft substrate
Bibliographic record
Abstract
On perfectly vertical surfaces, rolling is conventionally deemed impossible without external torque. While various species like geckos and spiders exhibit vertical locomotion, they cannot achieve rolling; instead, they fall. In this study, we demonstrate the spontaneous rolling of a soft polyacrylamide sphere on a soft polydimethylsiloxane (PDMS) substrate held vertically at a 90° incline, given specific elasticity values for the materials. Our experiments uncover a slow rolling motion induced by a dynamically changing contact diameter and a unique contact asymmetry. The advancing edge behaves like a closing crack, while the receding edge acts as an opening crack. Utilizing adhesion hysteresis theories and crack propagation models, we explain how this contact asymmetry generates the necessary torque and friction to maintain rolling, preventing either pinning or falling. The findings challenge the traditional understanding of vertical surface interactions and open new avenues for exploring soft-on-soft contact systems. This novel phenomenon has potential implications for designing advanced materials and understanding biological locomotion on vertical surfaces.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".