publications
Scientific breakthroughs achieved using the NanoOne from renowned institutes
AIP Publishing – Physics of Fluids, Kiss et al., 2026
Bridging shallow flow theory and microfluidics: The role of confinement in shaping wake lengths and pressure loss
Flow past obstacle clusters in micro-channels is central to a wide range of microfluidic applications, yet its fundamental hydrodynamics remain poorly understood under strong geometric confinement.
No-slip boundary conditions on all walls enforce inherently three-dimensional (3D) flow structures in fully confined micro-channels, fundamentally altering wake formation, momentum transport, and drag mechanisms. A combined experimental and numerical investigation of wake dynamics behind obstacle clusters in laminar micro-channel flows is presented. High-resolution micro-particle image velocimetry and resolved 3D computational fluid dynamics simulations are employed to systematically explore the effects of Reynolds number and cluster porosity. We demonstrate that full wall confinement suppresses classical wake–regime transitions commonly observed in shallow and unconfined flows, including shear layer instabilities and vortex shedding. Instead, wake recovery is governed primarily by secondary flows that promote rapid momentum redistribution across the channel depth. As a result, wake length exhibits only weak dependence on Reynolds number and is controlled predominantly by cluster porosity. We further introduce the relative bleeding velocity as a unifying metric to characterize the transition from macro-particle to individual particle behavior. The relative bleeding velocity is the ratio of the mean velocity through the cluster’s main axis perpendicular to the inflow and the mean inflow velocity. These findings establish a distinct physical regime of confined wake flows, bridging the gap between classical shallow flow theory and microfluidic hydrodynamics, and provide a foundation for improved prediction of pressure losses, transport, and mixing in micro-reactors and porous microfluidic systems.
On-chip fabrication of tailored 3D hydrogel scaffolds to model cancer cell invasion and interaction with endothelial cells
The high mortality associated with certain cancers can be attributed to the invasive nature of the tumor cells. Yet, the complexity of studying invasion hinders our understanding of how the tumor spreads. This work presents a microengineered three-dimensional (3D) in vitro model for studying cancer cell invasion and interaction with endothelial cells. The model was generated by printing a biomimetic hydrogel scaffold directly on a chip using 2-photon polymerization that simulates the brain’s extracellular matrix. The scaffold’s geometry was specifically designed to facilitate the growth of a continuous layer of endothelial cells on one side, while also allowing for the introduction of tumor cells on the other side. This arrangement confines the cells spatially and enables in situ microscopy of the cancer cells as they invade the hydrogel scaffold and interact with the endothelial layer. We examined the impact of 3D printing parameters on the hydrogel’s physical properties and used patient derived glioblastoma cells to study their effect on cell invasion. Notably, the tumor cells tended to infiltrate faster when an endothelial cell barrier was present. The potential for adjusting the hydrogel scaffold’s properties, coupled with the capability for real-time observation of tumor-endothelial cell interactions, offers a platform for studying tumor invasion and tumor–endothelial cell interactions.
High-resolution bioprinting
Since the inception of 3D printing in the 1980s, there have been remarkable advancements that have given rise to a wide array of technologies. In the field of bioprinting, many of these technologies are being leveraged to embed living cells into precisely defined 3D structures. Droplet- and extrusion-based bioprinting, two of the earliest techniques, have undergone significant improvements but still face limitations in resolution and versatility. As the role of the cellular microenvironment becomes increasingly recognized, the need for technologies that operate at the microscale has become more critical. Among high-definition (HD) bioprinting techniques, which achieve resolutions below 50 µm, multiphoton lithography (MPL) stands out for its unparalleled precision and versatility. MPL uses a laser to initiate a chemical reaction within a photosensitive material at the laser’s focal point, resulting in highly precise and truly 3D printing capabilities. Recent innovations have focused on improving cytocompatibility and increasing throughput to levels suitable for creating tissue-relevant structures. UpNano leverages over a decade of expertise in photoinitiator and material development, combined with advanced hardware and sophisticated software solutions, to deliver MPL-based bioprinting at the highest level. In addition to classic photopolymerization, additional processes like photoablation, photocleaving, and photopatterning enable precise temporal and spatial control over cell microenvironments. These photochemical methods hold great promise for enhancing the complexity and functionality of 3D-printed tissue models. As commercial MPL systems become more widespread, a growing number of biofabrication applications are emerging, ranging from organs-on-a-chip, designed to replace animal testing, to tissue engineering, where microscaffolds are used to create millimeter-sized tissue constructs, and vascularization, where MPL’s precision allows for the creation of microvessels.
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