Microbe removal using a micrometre-sized optical fiber.

The growing global shortage of fresh water has lead to the need for technological innovations for water purification and reuse. The removal of pathogenic microbes from urban, laboratory or industrial wastewater is one of the most challenging and critical issues due to the potential risk of microbe outbreaks. In addition, microbe removal in human blood or tissues has also inspired novel techniques for extracting and collecting different cells in fluidic channels or vessels. Recently, efficient removal of microbes from flowing water running under gravity feed has been achieved using filters in nanotubes or nanofibers. Here we report a highly efficient removal of microbes from flowing water in a fluidic channel using a reusable micrometre-sized optical fiber. Our technique is based on photophoresis of the microbes induced by the radiation of 1.55 μm wavelength injected into the fiber. Yeast cell suspensions, as a sample of microbe-contaminated water, are flown through a fluidic channel and the suspended cells are collected by the photophoretic forces, leading to a consistent accumulation of the yeast cells. The experiments indicate that a removal efficiency of 99.9% can be obtained when the flow velocity of the suspensions is less than the peak photophoretic velocity of the yeast cells.