AC electrothermal trapping for efficient nanoparticles enrichment in a microchannel

Trapping nanoparticles in a microfluidic device holds promise for enriching low-concentration species in samples. This article explores AC electrothermal (ACET) flow as an effective mechanism for nanoparticle trapping within a microfluidic system. Employing a precisely designed microfluidic device with coplanar symmetric electrodes, we systematically analyze the trapping performance of 100-nm polystyrene nanoparticles (PsNPs) dispersed in deionized water. Through fluorescence microscopy, we observe the dynamic behavior of PsNPs under the influence of an AC electric field. The concentration factor (CF) is introduced as a metric for evaluating trapping efficiency, revealing a remarkable up to 30-fold increase in concentration within the electrode gap. The quadratic relationship between electrothermal forces and electric field strength is investigated, highlighting the direct impact on trapping enhancement. By adjusting the applied voltage to vary the electric field strength, CF is found to significantly improve, reaching a peak value of 16.3 at 3.5 MV m⁻¹. Furthermore, we explore the influence of frequency on ACET velocity, emphasizing the importance of aligning frequency and electric field strength for effective nanoparticle trapping. This study contributes valuable insights into the optimization of ACET for precise and controlled nanoparticle manipulation, holding promise for diverse applications in fields requiring nanoparticle enrichment.