Electrokinetic Microscope for Imaging Three-Dimensional Surface Topography and Heterogeneity

We introduce the concept of electrokinetic microscope (EKM) which is an imaging technique based on hydrodynamics and electrokinetics. The EKM can provide information of the three-dimensional surface topography and heterogeneity using a syringe pump, pressure sensor, and electrometer. The three-dimensional surface topography is obtained from the relation between the flow impedance and a relative distance of a probe from a specimen, and the surface heterogeneity is obtained by measuring streaming potential or current electrokinetically generated by a surface material. Experimental results show that streaming potential and current depend not only on the relative distance between the probe and specimen, but also on surface materials. The major advantages of the EKM are that it does not need direct physical contact between the probe and specimen, and the surface topography and heterogeneity of the specimen are measured simultaneously. EKM micrographs of microscale patterns with various materials and linewidths are presented. The lateral resolution of the EKM strongly depends on the inner diameter of the probe.