arrive at an angle a u201c grazing u201d angle such that the directional and asymmetric pressure of the arriving phonons appears as wave motion on the other side of the catalyst body which pushes against a fluid such as a liquid metal or sacrificial interface causing it to move in a direction parallel to the bottom surface an apparent negative coefficient of friction between the wall and the fluid is exhibited due to the wave motion or directed impulses along the surface of the bottom of the device the exemplary device comprises a substrate 202 with top and bottom surfaces having a saw tooth pattern as shown in the cross sectional view of fig2 the bottom surface is in contact with a hydraulic fluid 204 as shown in fig2 the substrate can be thought of as comprising a plurality of sub structures 200 having rectangular cross sections and arranged adjacent to each other at an angle with respect to the hydraulic fluid 204 at the top surface of the substrate each sub structure 200 includes a layer 201 comprising a catalyst on an exposed side surface between adjacent sub structures each sub structure 200 includes a layer 202 of material which.