Fig. 4.

Selective cargo assembly and transport. a Precise control of the frequency of the applied field enables selective transport (green highlighted region). The desired operating frequency is chosen to align with positive DEP of target (magenta) and negative DEP of the contaminant (purple). The frequency of the applied field also determines the mode of transport—whether by ICEP with Ps hemisphere forwards or sDEP with metallic hemisphere forwards. Operating conditions can be determined by plotting the frequency-dependent mobility (particle velocity normalized by the maximum attainable value U₀ = 2.4 μm s⁻¹) JP carrier (blue data points) and the real part of the Clausius–Mossotti factor of target and contaminant (magenta and purple curves). Four frequency domains are observed—each of which correspond with microscope images and schematics in b–e. b At low frequencies, target and contaminant undergo pDEP (non-selective trapping), whereas JP translates forward under ICEP. c Janus particle reverses direction but both target and contaminant still undergo pDEP. d Selective trapping—target undergoes pDEP, while contaminant undergoes nDEP. e Frequency aligned with nDEP of target for release. Scale bar in b is 5 µm