Gold-coated fiber concentrates bacteria

Osaka Metropolitan University researchers have developed a gold-coated optical fiber that concentrates bacteria and other microscopic targets into a single spot within about a minute, according to a study published in *Communications Physics*. The team said the method is designed to speed up detection when harmful bacteria are present only in trace amounts. The paper, published on February 19, 2026, describes a fiber tip coated with a metallic thin film that turns laser light into localized heat. (nature.com 1) (nature.com 2) The university said on May 18 that the system can gather thousands to hundreds of thousands of bacteria or microparticles from a 20-microliter sample in 60 seconds. Lead author Takuya Iida said conventional techniques can be slow, complex, or limited to collecting targets near a surface. ### How does the fiber actually pull bacteria together? The device works by heating the liquid at the fiber tip. Osaka Metropolitan University said the gold-coated tip absorbs the incoming laser light, converts it into heat, and creates both fluid motion and microscopic bubble formation in the surrounding liquid. (nature.com) Those effects generate three-dimensional convection currents. The paper said the currents move bacteria and particles through the liquid and concentrate them between the bubble and the fiber tip, rather than only along a flat surface. (omu.ac.jp) Iida said that differs from conventional photothermal techniques that mainly operate in two dimensions. ### What did the researchers say it improved over existing methods? The study reported that the module assembled 10^3 to 10^5 bacteria and microparticles from a 20-microliter sample within 60 seconds when positioned away from the substrate. (omu.ac.jp) The authors said that represented more than a tenfold increase in assembly efficiency compared with conventional two-dimensional photothermal methods. Osaka Metropolitan University said the system achieved about tenfold higher collection efficiency than conventional approaches and enabled the assembly of roughly 10,000 microparticles or bacteria in 60 seconds. (omu.ac.jp) Iida said the results showed that complex optical setups were not required to achieve high-efficiency concentration in liquid environments. ### Which bacteria and use cases did the paper focus on? The paper identified *Staphylococcus aureus* and *Escherichia coli* as examples of harmful bacteria that are important to detect accurately. (nature.com) The authors wrote that *E. coli* O157 can cause severe illness even at concentrations of 10 to 100 cells. The researchers framed the method as a tool for early diagnosis and disease prevention. The paper said the same optical-condensation approach could also be relevant to nanoscale biomarkers, drug delivery and material assembly technologies. (omu.ac.jp) ### Who conducted the work? The *Communications Physics* paper lists Kota Hayashi, Mamoru Tamura, Masazumi Fujiwara, Shiho Tokonami and Takuya Iida as authors. Osaka Metropolitan University identified Iida as a professor in its Graduate School of Science and Research Institute for Light-induced Acceleration System, or RILACS. (nature.com) Osaka Metropolitan University said the next step is broader use of the fiber-based optical condensation method for faster, more sensitive detection of bacteria and other micro- and nanoscale targets. (nature.com) The open-access paper remains available through *Communications Physics*, where the full experimental setup and results are published. (nature.com)