Reconfigurable Particle-Walled Fluidics for Adaptive Biomedical and Chemical Interfaces

There is growing interest in open fluidic systems—designs where liquids are no longer confined within rigid walls but are instead allowed to interact freely with the surrounding environment. By removing barriers, researchers can now explore interactions that were previously difficult or impossible to access—such as direct gas exchange, localized biochemical reactions, or cell behavior under ambient conditions. Yet, for all their conceptual appeal, open fluidic devices present serious practical hurdles. Liquids, when stripped of their enclosures, behave unpredictably. They spread, deform, or evaporate with even modest flow rates or temperature shifts. Designing systems that can support stable liquid shapes—especially under dynamic conditions—has proven extremely difficult. Some workarounds have emerged: oil overlays to reduce evaporation, or interfacial tension tricks using immiscible liquids. Others have turned to complex microfabrication, using lithography or 3D printing to carve out precise topographies. However, these approaches are limited because immiscible phases often interfere with biological compatibility, and high-end fabrication is inaccessible to many labs and ill-suited to rapid iteration. Worse still, most of these systems are fixed in design and changing a channel layout typically means starting from scratch.

Faced with these limitations, new research paper published in Advanced Materials and conducted by Heng Liu, Xianglong Pang, Mei Duan, Zhujun Yang, and led by Professor Xiaoguang Li from the Northwestern Polytechnical University alongside Professor Thomas Russell from University of Massachusetts, took a very different approach. Rather than relying on rigid enclosures or exotic materials, they embraced a strategy rooted in the behavior of particles at interfaces. Hydrophobic powders—readily available and easy to manipulate—can, when assembled at the surface of a droplet, create a jammed shell that mimics the function of a solid boundary. These particle layers stabilize the liquid form, resist deformation under flow, and maintain structural fidelity, all while leaving the surface accessible to the environment.

But this wasn’t just a technical workaround. It was a deliberate response to a broader need—especially in biomedical research, where adaptability and spatial control are often non-negotiable. Think of drug response assays where tumor cells must be exposed to carefully controlled gradients, or thermally driven therapies requiring localized heating. A platform that’s reconfigurable, transparent, and simple to assemble could open up entirely new experimental possibilities—without demanding a cleanroom or a corporate-sized budget. That vision underpins this study.

The researchers set out to develop open fluidic channels using an approach that was both elegant in concept and refreshingly low-tech. Starting with ordinary Petri dishes, they laser-patterned adhesive tape to create precise hydrophilic pathways, flanked by superhydrophobic surfaces derived from a sol-gel coating. This allowed them to control where the liquid would travel without resorting to closed channels. When droplets coated with hydrophobic particles—ranging from nanoscale SiO₂ to larger carbon nanotube (CNT) agglomerates—were introduced, the liquids pinned cleanly to the patterned regions, forming stable channels. The particle shell played a crucial role here: by jamming at the liquid-air interface, the particles acted like a flexible scaffold, imparting a pseudo-solid structure to the droplet and minimizing distortion under flow. To rigorously assess this effect, the authors used barbell-shaped channel designs and tracked how the inlets expanded under pressure. In devices without any particle reinforcement, liquid inflation was dramatic and uncontrollable. In contrast, channels bordered by particle walls remained remarkably stable—even at elevated flow rates—showing less than 15% deformation. The contrast was not only visual but quantifiable, offering a compelling argument for the stabilizing power of interfacial jamming. Afterward, the authors examined the effect of particle size and morphology on mechanical performance of the wall by comparing different hydrophobic powders. Using Langmuir–Blodgett compression assays, they measured the bending modulus of the interfacial films and found that micron-scale powders like lycopodium and PTFE produced far stiffer, more robust walls than nanoparticle monolayers. These thicker particle coatings enabled fluidic structures to withstand flow rates of up to 8.9 mL/min, nearly doubling what nanoscale films could tolerate. Simulations of the pressure and velocity fields within the channels backed this up, showing more stable flow profiles when particle walls were present.

One of the most compelling aspects of this system was its modularity. By using so-called “liquid plasticines”—shapable liquid systems entirely enveloped in particles—the researchers could assemble, disassemble, and reconfigure circuits mid-experiment. These mobile bridges allowed them to create reusable reaction platforms, where the same layout could be redirected multiple times just by shifting a single liquid plasticine. They further exploited this versatility to build three-dimensional structures. By stacking particle-encased flows and connecting them with fly-over bridges, they maintained flow separation even in vertically layered systems. Finally, to test the biological relevance, they introduced osteosarcoma cells and created a gradient of cisplatin. Cell viability decreased in a dose-dependent manner. When CNT walls were irradiated with NIR light, localized heating enhanced drug uptake, significantly increasing tumor cell death—a strong proof-of-concept for integrating photothermal effects into an open fluidic system.

In conclusion, Professor Xiaoguang Li and colleagues successfully used hydrophobic particles to stabilize liquids at the air–interface and show that you don’t need hard infrastructure to guide flow—you just need a smart manipulation of surface energy and interfacial mechanics. The result is a fluidic system that is not only simpler to build but also inherently more versatile. What stands out is the accessibility of the method. There’s no need for cleanrooms, no reliance on expensive polymers or proprietary microfabrication. It’s a toolkit built from a very cheap laser marking machine and everyday lab materials—Petri dishes, adhesive tape, and a handful of commercially available powders. Yet, the capabilities unlocked are anything but basic. The ability to reconfigure flow paths in real time—by merging, moving, or reshaping particle-coated droplets—introduces a degree of flexibility that conventional chips simply cannot match. You can now redesign your fluidic logic mid-experiment, without ever needing to halt the process or fabricate a new device.

What’s perhaps most impactful is the biological relevance. In their cancer therapy experiments, the researchers used the platform to deliver controlled cisplatin gradients across cultured osteosarcoma cells. Then, by integrating carbon nanotube walls, they leveraged local photothermal heating to enhance drug uptake. This dual-modality—combining chemical delivery with spatially precise thermal activation—mirrors real therapeutic strategies currently being explored in oncology, yet it was achieved here with a system made almost entirely by hand. Indeed, the new innovation empowers low-resource labs while offering advanced functionality for complex applications. On the engineering side, the ability to build multilayered, three-dimensional fluid networks that remain stable under flow pressure is a technical leap. This opens up possibilities for modeling more anatomically realistic environments, where flows need to cross or interweave without mixing. And because the system is open to air, natural processes like gas exchange or evaporation aren’t hindered—they become tools to work with.