Microparticle electrical conductivity measurement using optoelectronic tweezers
Wei Ren, Mohammad Asif Zaman, Mo Wu, Michael A. Jensen, Ronald Wayne Davis, Lambertus Hesselink
Abstract
When it comes to simulate or calculate an optoelectronic tweezer (OET) response for a microparticle suspended in a given medium, a precise electrical conductivity (later referred to as conductivity) value for the microparticle is critical. However, there are not well-established measurements or well-referenced values for microparticle conductivities in the OET realm. Thus, we report a method based on measuring the escape velocity of a microparticle with a standard OET system to calculate its conductivity. A widely used 6 μm polystyrene bead (PSB) is used for the study. The conductivity values are found to be invariant around 2×10-3 S/m across multiple different aqueous media, which helps clarify the ambiguity in the usage of PSB conductivity. Our convenient approach could principally be applied for the measurement of multiple unknown OET-relevant material properties of microparticle-medium systems with various OET responses, which can be beneficial to carry out more accurate characterization in relevant fields.