New method boosts control and separation of tiny particles – a promising tool for medical research

Separating nanosized particles remains a persistent challenge in biotechnology. Once particle size drops below a few hundred nanometres, their behaviour becomes dominated by diffusion – the random walk of particles. This weakens the forces used to guide them, causing separation accuracy to collapse.

A microfluidics research group led by Professor Caglar Elbuken at the University of Oulu has developed a new solution to the problem. The method significantly improves the separation and purification of both small synthetic particles and nanoscale vesicles secreted by living cells.

Particle separation is crucial because many biological processes occur precisely at the nanoscale. Extracellular vesicles isolated from biological samples can reveal early changes in the body. If impurities cannot be removed, valuable information may remain undetected. An efficient yet gentle purification method is therefore essential for both diagnostics and basic research.

In the new method, the researchers combined two physical phenomena: lift generated by electrophoretic slip and the lateral forces that arise in a viscoelastic fluid. In the slip phenomenon, an electric field does not pull the particle directly but sets the surrounding fluid in motion. A viscoelastic fluid behaves partly like a conventional liquid and partly like an elastic material, resulting in lateral forces that do not emerge in water-based solutions.

The study was recently published in the respected journal Analytical Chemistry. The article’s lead author, doctoral researcher Seyedamirhosein Abdorahimzadeh from the University of Oulu, explains the significance of the work:

“Controlled separation of nanoparticles is essential in both biological research and many clinical applications, yet existing methods are often slow, complex or unreliable. Our separation and purification method enables surprisingly efficient sorting of particles in an ordinary microchannel. Until now, particles of this size required nanofluidic channels, which clog easily and demand high operating pressures. Compared to earlier techniques, the new method is faster, more accurate and easier to scale.”

The study demonstrated that the method improves the separation and purity of polystyrene particles by roughly 30–50%. Polystyrene particles are commonly used as model particles in research because their size, shape and surface properties can be manufactured with high precision. This makes them ideal test material for various separation techniques, such as those used in microfluidics. The researchers also succeeded in enhancing the purity of vesicles secreted by cancer cells by more than one fifth – a significant improvement at this scale.

According to the researchers, the method could be applied in the future in blood sample analysis, cancer research, studies of cellular communication and nanomedicine more broadly.

The research forms part of Abdorahimzadeh’s doctoral thesis, which examines electroviscoelastic and electroinertial methods for controlling and separating micro- and nanoscale particles. He will defend his dissertation on Friday, 13 February 2026, at the University of Oulu.

Article: Seyedamirhosein Abdorahimzadeh, Zikrullah Bölükkaya, Éva Bozó, Artem Zhyvolozhnyi, Anatoliy Samoylenko, Feby W. Pratiwi, Henrikki Liimatainen, Seppo J. Vainio, and Caglar Elbuken. Microfluidic Electro-Viscoelastic Separation of Submicron Particles and Extracellular Vesicles. Analytical Chemistry, February 6, 2026. DOI: 10.1021/acs.analchem.5c06727

Further information about Abdorahimzadeh’s dissertation defence