Electrokinetic Tweezers Drive 20 nm-Precision Micro-Robot Sensing of Biomolecular Patterns in Liquids

The preprint validates a motion-enabled scheme using electrokinetic tweezers that position particles at up to 20 nm precision to steer motors along programmed paths. Local chemical or topographic variations alter motor speed and trajectory, converting locomotion data into sensing signals without physical tethers. This approach operates directly in liquids, sidestepping the cantilever constraints and tip-sample damage risks that limit atomic force microscopy on soft biological interfaces. Sample size is a proof-of-concept demonstration on defined microridge arrays and patterned biomolecules; key limitation is restriction to controlled buffer conditions without in-situ biological variability testing.

Context from related electrokinetic and microrobotic literature shows this work advances beyond earlier tethered or magnetically steered probes by achieving wireless, solution-compatible scanning at nanoscale resolution. Prior studies on catalytic motors lacked the closed-loop field confinement needed for repeatable path following, while AFM papers routinely note liquid-cell incompatibilities for delicate tissues. The concrete engineering gain here lies in the dual-use of the same field for both propulsion and position feedback, reducing hardware complexity for potential deployment in microfluidic environmental monitors or minimally invasive medical diagnostics.

Next steps require closed-loop autonomy with onboard sensing and validation against gold-standard surface techniques on heterogeneous samples. Integration with machine-learning trajectory analysis could extract quantitative material properties from motion statistics, moving the platform toward industrial surface metrology where conventional probes cannot reach.