Microparticle/Fiber Synthesis

"Microfluidics" can be used for the multi-functional manufacturing of ultra-fine fibers and microparticles. This article will describe them in detail.

Microfluidic Microfiber Manufacturing

In recent years, microfibers/nanofibers have been widely used in tissue engineering and regenerative medicine. Microfibers/nanofibers can mimic the natural condition of tissues in which fibrils are entangled in the matrix, and are excellent candidates for cell culture scaffolds. After continuous development, microfluidic technology can be used to produce microfibers, which precisely control the anisotropy of morphology, material, size and structure, and biological applications. To date, various technologies have been developed for manufacturing various types of microfibers with various materials and morphologies.

Synthetic Methods of Superfine Fiber

Microfluidics has created a wide range of methods for the custom manufacturing of microfibers. It is related to laminar flow, allowing two or more liquid streams to flow side by side without mixing, which is beneficial for microfiber manufacturing. For example, two polymer streams with different properties can be adjacent to each other and then photo-crosslinked to make bi-material microfibers. By changing the arrangement of the fluid flow, different microfibers can be formed.

Crosslinking is an important step in the production of microfibers. The appropriate crosslinking method depends on the type of polymer and the desired morphology of the microfiber. There are three common techniques for curing microfibers:

• Photocrosslinking: This method requires a photopolymerizable polymer to crosslink the polymer.
• Chemical crosslinking: In this method, small molecules or ions cause crosslinking. Microfibers can be cross-linked to varying degrees on the chip or be crosslinked off-chip.
• Solvent extraction: Crosslinking occurs through phase inversion. The sheath flow and the polymer flow through the microchannel and form a coaxial flow. The solvent in the polymer is exchanged with the sheath liquid to solidify the microfibers.

Types of Microfibers

Our microfluidic chip allows the manufacturing of microfibers with uniform shapes and sizes, ranging in size from a few microns to hundreds of microns. Nanofibers can also be realized by modifying the input material. For example, microfluidic chips can easily produce cell-rich microfibers for regenerative medicine and tissue reconstruction. In addition, nanoparticles, proteins or drugs can also be mixed with input materials and encapsulated in microfibers for therapeutic purposes.

Alfa Chemistry's microchips provide unprecedented flexibility in changing the structure of microfibers, including but not limited to:

• Hollow microfiber
• Multi-component microfiber
• Concentration gradient microfiber
• Microfibers with different core materials

Microfluidic Particle Synthesis

Two crucial characteristics of particles: morphology and uniformity. Microfluidics technology has proven to be a powerful tool to generate uniformly sized particles in spherical and custom shapes. In microfluidics, droplet microfluidics is an excellent choice for spherical particles, while photolithography is suitable for custom-shaped particles.

Spherical Particles

Spherical particles are the most common form of particles formed using microfluidic chips. Droplet microfluidics is the most popular method of spherical particle generation, which allows very high particle generation frequencies of the order of kHz. In this technique, a liquid stream is split into droplets by another stream. The droplets then undergo a chemical reaction to solidify and form spherical particles. In this way, the particles are uniform in height and size.

Depending on the polymer solution used, the curing method can be different. Common methods include:

• Thermal polymerization: The droplet undergoes a temperature change to solidify.
• Photopolymerization: The droplets are polymerized by exposure to ultraviolet light.
• Chemical polymerization: The third solution is mixed with droplets to solidify.

Click on Droplet-based Microfluidics and Droplet Generation Chips to learn more about droplet microfluidics and droplet generation chips.

Custom-shaped Particles

We can produce particles of the desired shape and structure. There is no need for a droplet generator chip. Instead, a photomask of the desired shape should be used. The photomask is located on the straight channel through which the photo-crosslinkable material passes. A UV lamp is turned on on the top of the photomask, which passes through the printed shapes on the photomask and crosslinks the material underneath. Then the custom-shaped particles are punched out of the chip.

Reference

• Sommer C, et al. (2014). "The Equilibrium Velocity of Spherical Particles in Rectangular Microfluidic Channels for Size Measurement." Lab Chip. 14: 2319-2326.

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