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Microneedle delivery methods to the epidermis can be divided into four types: ligation followed by application (solid microneedles), ligation followed by release (soluble microneedles, frozen microneedles), coated delivery (coated microneedles), and injectable delivery (hollow microneedles, gel microneedles). Etching technology and MEMS processing technology are generally used to prepare microneedles with sufficient mechanical force, mostly for preparing solid microneedles, hollow microneedles, and coated microneedles, while photolithography is mostly used to prepare soluble microneedles.
Fig.1 Graphical description of the manufacturing process of microneedles. (Choi et al., 2022)Microneedle preparation technology has the following characteristics: (1) low cost, simple preparation, and easy mass production; (2) high retention of the hollow structure and geometry of traditional hypodermic needles, high drug loading capacity, and good puncture performance; (3) minimally invasive, painless, high biosafety, and high patient compliance.
Different types of microneedles require different preparation techniques, mainly because of the different nature of the materials selected. With the development of various technologies, more and more materials can be used to prepare microneedles, from the earliest silicon materials to metals to polymer materials, and the preparation technologies that can be chosen include 3D printing technology, etching technology, photolithography and microelectromechanical system processing technology.
3D printing technology can process and take into account the characteristics of fast, high precision and large format, which can meet the above micro-needle size requirements, and the processed micro-needle surface is smooth, which provides technical support for the micro-needle minimally invasive and painless treatment effect, and also provides a feasible solution for fast and efficient industrial production.
(1) Remove the bare oxide layer on the surface of the material, the part covered by the photosensitizer remains on the surface of the material in a needle-like structure. The removal of the oxide layer can be done by chemical dissolution removal or by physical impact removal.
(2) The photosensitizer at the tip of the needle-like structure is degraded by UV light, and the degradation products are washed away with solvent to collect the microneedles.
Photolithography is a simple microneedle preparation process that allows precise control of microneedle size, shape, and preparation material. The steps for preparing microneedles by photolithography:First, a polymer film is paired with a microneedle mold and filled with a heated roller, then the filled mold is placed on a flexible substrate, and then the mold is separated by the heated roller, and the microneedles are retained on the substrate material to make a microneedle patch.
MEMS technology can also be called surface/bulk micromachining technology, is a micron or submicron level fine processing technology by large machine manufacturing small machine and then use small machine manufacturing micro-machine. Microelectromechanical systems are micro devices or systems that can be fabricated in bulk, integrating micro mechanisms, micro sensors, micro actuators and signal processing and control circuits, down to interfaces, communications and power supplies.
Different types of microneedles can be prepared by different classes of techniques, and since the tip size, geometry, and number of tip arrays affect the mechanical properties of microneedles, CD Formulation can visualize the geometry of microneedles by visual inspection, stereo microscopy, and scanning electron microscopy (SEM). If you are interested in our technology, please feel free to contact us.
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