Adaptive Open Fluidics: Particle-Stabilized Liquid Channels for Biomedical and Chemical Applications

Fluidics, the study of how liquids move through channels, has played a huge role in everything from chemical analysis to medical research. When microfluidics came along, it completely changed the game, making experiments far more precise. Suddenly, lab-on-a-chip devices, point-of-care diagnostics, and high-throughput screening became possible. But despite all these advancements, traditional fluidic systems still have one major limitation—they are trapped inside enclosed channels. This might be great for controlling flow, but it also means the liquid cannot interact freely with its surroundings. That is a big problem in situations where gas exchange, real-time adjustments, or flexible reconfiguration are needed. This is where open fluidics comes in. Instead of keeping liquid locked inside walls, this approach allows it to stay exposed to air while still following structured pathways. The idea sounds simple, but it opens up a world of new possibilities. It could completely change how researchers conduct cell culture studies, chemical experiments, and environmental monitoring, all of which require direct interaction between the liquid and outside elements. The challenge, however, is that working with open liquids is not easy. Fluids evaporate, shift unexpectedly, or lose their shape without some kind of physical boundary. And if scientists want a system where they can adjust pathways on demand, things get even more complicated.

To this account, new research paper published in Journal of Advanced Materials and conducted by Heng Liu, Xianglong Pang, Mei Duan, Zhujun Yang and led by Professor Xiaoguang Li from the School of Physical Science and Technology, Northwestern Polytechnical University alongside Professor Thomas Russell from University of Massachusetts have come up with a completely new way to build open fluidic systems. Their study developed a method that stabilizes liquids using tiny hydrophobic particles which naturally gather at the liquid-air interface and create a flexible but stable barrier that prevents the fluid from spilling or breaking apart. The researchers put their innovative open fluidic system to the test, focusing on how well it could be built, how stable it was under different conditions, how easily it could be adjusted, and whether it had real-world biomedical applications. They kicked things off with a straightforward yet clever fabrication method, using laser-patterned surfaces that had a mix of hydrophilic and hydrophobic areas. This setup made it possible to control exactly where liquids were placed while preventing them from spreading in unwanted directions. Since the system lacked physical walls, they needed a way to keep everything in place, so they turned to hydrophobic nanoparticles and microparticles. These particles formed natural barriers around the liquid, helping it hold its shape while still allowing interaction with the surrounding environment.

With their basic structures in place, the team shifted their focus to stability testing. In most open liquid systems, fluids tend to lose their shape under pressure, expanding or collapsing unpredictably. To see how well their approach held up, they compared different particle coatings—some fluidic channels were reinforced with a thin monolayer of nanoparticles, while others used micron-sized powder particles like PTFE and carbon nanotubes (CNTs). The results were striking. Channels without any reinforcement lost their shape almost immediately, but those stabilized with nanoparticles performed much better. The real winner, however, was the microparticle-covered channels, which proved to be the most structurally rigid, handling flow rates up to 8.9 mL/min—nearly double what the nanoparticle-covered channels could sustain. This showed that larger particles created a stronger mechanical barrier, making them ideal for situations that required consistent, controlled fluid movement. Beyond just keeping liquid in place, the authors wanted to prove their system could be reconfigured on demand, something that is almost unheard of in microfluidic systems. They developed a method to reshape and reconnect liquid pathways using a simple fusion process where they could manually move liquid bridges covered in particles to create new connections or disconnect old ones. Afterward, the team tackled three-dimensional (3D) open fluidics, an area that has remained mostly unexplored. Traditional fluidic devices are almost always flat, making it difficult to simulate complex interactions or run multiple reactions at once. The team stacked liquid channels stabilized with particles, creating fluid streams that could move independently, passing over and under each other without mixing. They even built “fly-over bridges,” allowing one stream of liquid to cross over another while maintaining full separation. This was a game-changer, proving that multi-layered, open fluidic systems can be created without needing rigid support structures. These capabilities could be invaluable for organ-on-a-chip models, where multiple biological processes need to interact just like they do in the human body. To put their innovation into real-world biomedical applications, the researchers designed a fluidic network that mimicked chemotherapy treatment, exposing osteosarcoma (143B) cells to a controlled drug gradient. By allowing cis-platinum, a widely used chemotherapy drug, to flow through a gradually changing concentration, they could simulate how different doses affect cancer cell survival and their results were clear—cells exposed to higher drug concentrations had significantly lower survival rates, something confirmed by live/dead staining and CCK-8 viability tests. This experiment showed that their system could serve as an effective, adaptable drug screening platform, offering a cheaper and more flexible alternative to traditional cell culture methods.

Pushing the boundaries even further, the researchers tested whether heat could improve chemotherapy effectiveness. They used CNT-coated fluidic channels to trap heat through near-infrared (NIR) laser irradiation, raising the temperature of the liquid inside. The temperature in CNT-covered channels shot up to 42.8°C, while the nanoparticle-coated ones barely changed. When cancer cells were treated with both chemotherapy and localized heating, survival rates dropped dramatically compared to chemotherapy alone. The researchers concluded that higher temperatures made cancer cells absorb more of the drug, reinforcing the idea that thermal modulation could be a powerful tool in improving chemotherapy treatments.

Prof. Xiaoguang Li said: Open fluidics combined with functional surface particles like CNT really opens up a bunch of new possibilities. We can rethink traditional studies in fresh ways and also explore totally new areas. In conclusion, Professor Xiaoguang Li and his colleagues have successfully introduced an exciting new way to build open fluidic devices which expected to shake up the field of fluidic engineering. Instead of relying on rigid enclosures like traditional microfluidic systems, their innovative method uses self-assembled particle walls to stabilize liquid channels while still keeping them open to the environment. This we believe is a huge step forward because it removes many of the long-standing challenges in fluidics, like restricted gas exchange, limited flexibility, and complex fabrication processes. By allowing liquids to interact freely with their surroundings, these devices open up entirely new possibilities for biomedical research, chemical synthesis, and advanced lab-on-a-chip technologies. Indeed, this work completely changes the way we think about liquid-based systems.