Figure 5

(a) Position of particles relative to the central wave node position (\(d_p\)) at different actuation amplitudes and translation speeds. The red, grey and blue regions represent the position \(x=0\) (underneath the upper plates), \(0<x<\lambda /4\) and \(\lambda /4<x<\lambda /2\) (stable collection). (b) Depiction of \(d_p\) under a capillary wave translating at a speed \(v_t\). The figure also depicts the forces acting on the particles during tweezing; \(F_d\) is the Stokes drag force due to capillary wave movement and \(F_{eq}\) is the equivalent collection force time-averaged over a cycle due to the periodic inertial drag from the capillary wave⁵⁶.