Additive manufacturing is an expanding multidisciplinary field encompassing applications including medical devices¹, aerospace components², microfabrication strategies^3,4 and artificial organs⁵. Among additive manufacturing approaches, light-based printing technologies, including two-photon polymerization⁶, projection micro stereolithography^7,8 and volumetric printing^{9,10,11,12,13,14}, have garnered significant attention due to their speed, resolution or potential applications for biofabrication. Here we introduce dynamic interface printing, a new 3D printing approach that leverages an acoustically modulated, constrained air–liquid boundary to rapidly generate centimetre-scale 3D structures within tens of seconds. Unlike volumetric approaches, this process eliminates the need for intricate feedback systems, specialized chemistry or complex optics while maintaining rapid printing speeds. We demonstrate the versatility of this technique across a broad array of materials and intricate geometries, including those that would be impossible to print with conventional layer-by-layer methods. In doing so, we demonstrate the rapid fabrication of complex structures in situ, overprinting, structural parallelization and biofabrication utility. Moreover, we show that the formation of surface waves at the air–liquid boundary enables enhanced mass transport, improves material flexibility and permits 3D particle patterning. We, therefore, anticipate that this approach will be invaluable for applications where high-resolution, scalable throughput and biocompatible printing is required.

Microfluidic organ-on-chip models recapitulate increasingly complex physiological phenomena to study tissue development and disease mechanisms, where there is a growing interest in retrieving delicate biological structures from these devices for downstream analysis. Standard bonding techniques, however, often utilize irreversible sealing, making sample retrieval unfeasible or necessitating destructive methods for disassembly. To address this, several commercial devices employ reversible sealing techniques, though integrating these techniques into early-stage prototyping workflows is often ignored because of the variation and complexity of microfluidic designs. Here, we demonstrate the concerted use of rapid prototyping techniques, including 3D printing and laser cutting, to produce multi-material microfluidic devices that can be reversibly sealed. This is enhanced via the incorporation of acrylic components directly into polydimethylsiloxane channel layers to enhance stability, sealing, and handling. These acrylic components act as a rigid surface separating the multiple mechanical seals created between the bottom substrate, the microfluidic features in the device, and the fluidic interconnect to external tubing, allowing for greater design flexibility. We demonstrate that these devices can be produced reproducibly outside of a cleanroom environment and that they can withstand ~1 bar pressures that are appropriate for a wide range of biological applications. By presenting an accessible and low-cost method, we hope to enable microfluidic prototyping for a broad range of biomedical research applications.

Gelatin Methacryloyl (GelMA) hydrogels are widely utilized in biomedical applications due to their biocompatibility and tenable mechanical properties. Traditional methods for measuring stiffness are often destructive, which limits real-time monitoring of critical processes such as swelling and cell growth. Here, Surface Acoustic Wave (SAW) sensing is employed to characterize the mechanical properties of GelMA hydrogels with varying concentrations and degrees of functionalization. GelMA samples were fabricated and subjected to compression testing alongside SAW measurements to assess stiffness via wave attenuation. While mass load affects wave reflection linearly, wave attenuation is an exponential response and the primary influence on stiffness measurements, with SAW sensing yielding greater reproducibility than compression testing. This indicates enhanced reliability and sensitivity in measuring dynamic property changes. Rayleigh-SAW technology has been successfully applied to 3D hydrogels, enabling real-time monitoring of cellular behavior and supporting advances in tissue engineering and other biomedical applications. Overall, SAW sensing offers a promising alternative to traditional mechanical testing, enhancing our ability to analyze complex biological systems.