Small molecule propulsion driven by solvent-mediated ultrafast energy transfer from vibrations to self-translation

Despite its interest, self-propulsion at the molecular scale remains an open challenge. In this work, we demonstrate through all-atom molecular dynamics simulations that vibrational excitation of the amphiphilic molecule nitromethane ( CH 3 NO 2 ) in water can lead to transient, directed propulsion. The excess vibrational energy is anisotropically transferred into the solvent, generating a mechanical instability that results in a short-lived net force between the solvent and the molecule. As a consequence, propulsion emerges along the axis of the molecule with speeds of up to 2.2 Å / ps , which decay in subpicosecond timescales. Under periodic excitation, this effect is measurable as an enhancement of the translational diffusion coefficient. We show that, despite being sensitive to the solute-solvent interaction model, the propulsion mechanism introduced here is robust to changes in the force field employed to describe atomic interactions. Our findings highlight a propulsion mechanism that is solvent-mediated and externally tunable via vibrational excitation, providing insight into the principles governing active transport at the nanoscale.