Fig. 2: Lawnmowers exhibit track-guided motion.

A Schematic illustrating LM motion within a lithographically defined peptide-containing channel with polymer resist walls and a SiO₂ channel floor that was selectively functionalized. LM beads have a density of 1.6 g/cm³ and are partially confined to the inside of channels by gravity. Channels are patterned in two directions as a control for possible background flow. B Trajectories of LMs on peptide lawns, colored from green to red to illustrate the time course of motion. Trajectories are overlaid with an image of the orthogonally patterned channels in the beginning of imaging (trajectories that started later are not depicted). The light blue arrows show the direction of slight background flow ( ≈ 0.01 µm/s). Scale bar is 50 μm. C, D Position along the channel direction as a function of time for (C) n = 48 LMs in peptide channels and (D) n = 26 particles in bare channels. The starting position of each LM is plotted with a common origin, with the positive direction chosen to align with the observed background flow in the channel. E, F Displacement distributions relative to Gaussian distributions. E Comparison of experimental and model results to Gaussian distributions. Plotted are the ratios of probability densities for the measured versus Gaussian-predicted distributions, where the first and second moments of the Gaussian distribution match experiment. Blue squares: peptide lawn from (C). Orange triangles: bare lawn from (D). Black circles: 1D LM model. The model captures the heavy tails seen for LMs on peptide lawns, while bare lawn trajectories are described by diffusion. F Displacement probability distribution of LMs in peptide channels has heavier tails than a Gaussian distribution, as seen also by the kurtosis of the distribution of κ = 3.3.