Method and device for fabricating step-index hydrogel optical fibers using hydrodynamic microfluidic focusing

This invention presents a novel microfluidic method and device for fabricating core-shell or concentric multilayered hydrogel structures with diameters as small as 100 micrometers, overcoming limitations of existing fiber production techniques.

Background:

Traditional methods that use coaxial devices to create core-shell hydrogel microfibers, including step-index hydrogel optical fibers —structures that transport light —often face challenges such as size constraints and clogging, limiting their usability—especially in delicate biomedical applications. There is a growing demand for microscale fibers that can be integrated seamlessly into in vitro tissue systems and various biohybrid devices. This need for miniaturized yet functional optical fibers has driven research toward innovative fabrication techniques that maintain fiber quality while reducing diameter size and increasing manufacturability.

Technology Overview:

This technology employs a hydrodynamic microfluidic focusing approach to fabricate hydrogel fibers and other concentrically layered hydrogel structures with precise geometric control. The platform is capable of producing solid fibers, core-shell fibers, hollow fibers, concentric multilayered fibers, and hydrogel optical fibers, including step-index architectures. The process begins by generating a laminar stream of core material, which may comprise hydrogel precursors, sacrificial fluids, or other functional materials. This stream is then concentrically surrounded by one or more laminar layers of hydrogel precursor, enabling the fabrication of solid, hollow, core-shell, or multilayered structures depending on the composition of the core and surrounding layers. The combined streams are subsequently focused through a converging sheathing flow to produce a stable coaxial stream with tunable dimensions. The resulting structure is then solidified using one or more suitable crosslinking mechanisms, including ionic, photochemical, thermal, or chemical crosslinking, yielding a mechanically stable hydrogel while preserving the intended architecture. This microfluidic platform enables the continuous production of core-shell microfibers, concentric bilayer hydrogel fibers, and other multilayered hydrogel geometries, each approximately 100 micrometers in diameter. Compared with traditional extrusion-based approaches, hydrodynamic focusing reduces the risk of clogging while enabling the fabrication of hydrogel structures with tunable sizes and architectures. Additionally, the device itself is 3D-printed, enabling accessible customization and scalability for various research and industrial needs. 
The resulting fibers are suitable for integration into complex tissue models and flexible biohybrid devices, making the technology highly relevant for biomedical engineering. The ability to continuously fabricate hydrogel fibers with controlled architecture expands practical opportunities across life sciences. For example, the platform enables large-scale fabrication of step-index hydrogel optical fibers for biomedical optical sensing and light delivery, and supports the production of hollow and multilayered tissue-engineered constructs.

Advantages:

•    The 3D-printed device has the capacity to fabricate core-shell hydrogel microfibers and may be implemented in any application requiring coaxial flow or coaxial fiber formation using coaxial devices, including, but not limited to, concentric needle, coaxial needle, coaxial nozzle, spinnerets, coaxial extrusion system, coaxial glass capillary, microfluidic chip-based coaxial devices.
•    Reduces clogging issues commonly encountered in traditional coaxial device-based concentric multilayer hydrogel manufacture due to microfluidic laminar flow design.
•    3D-printed device offers cost-effective, customizable, and scalable production capabilities.
•    When fabricated using suitable materials, the device can be compatible with standard sterilization methods, including autoclaving. Enables continuous fabrication of hydrogel fibers over a broad range of diameters and lengths. Enables fabrication of ultra-thin hydrogel microfibers down to 100 micrometers, surpassing existing size constraints. For example, a step-index fiber structure improves optical performance for biomedical sensing and imaging applications.
•    Cell-laden microfibers allow for cells’ access to oxygen and nutrients through diffusion, enabling high-density cell culture and manufacturing
•    Ideal for integration into biological environments, such as in vitro tissue systems and soft biohybrid devices.

Applications:

•    Biomedical engineering fields, including 3D culture, drug delivery systems, tissue engineering scaffolds, and diagnostic devices requiring microfibers.
•    Development of soft biohybrid devices where flexible and biocompatible optical components are essential.
•    Research and academic laboratories focused on bioprinting and regenerative medicine technologies.
•    Optical sensing and imaging within biological tissues at microscale dimensions.
•    Potential industrial applications in manufacturing customized hydrogel-based optical components.

Intellectual Property Summary: Patent pending

Stage of Development: TRL 4: The developed microfluidic flow focusing nozzle has been shown to functionally create hydrodynamically focused steady concentric layers. Validation for hydrogel formation remains ongoing; however, early results indicate that concentric layering is feasible. However, further optimization of sheathing flow rate and ionic crosslinker concentration is required, depending on material parameters.

Licensing Status: This technology is available for licensing.

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