Etching Technology for Microneedles Preparation

Microneedle patches consist of a series of short needle-like structures that penetrate the skin in a minimally invasive manner; their length can be customized so that they can bypass the stratum corneum and interact precisely with the underlying viable epidermis without touching the nerve endings or capillaries in the underlying dermis. The use of etching techniques to develop microneedle structures reduces processing time and complexity, achieving the complex shapes and micron-level precision required to successfully fabricate microneedles.

Fig.1 Key steps in the fabrication of a microneedle/reservoir device. (O'Mahony et al., 2023)

What are the Etching Technologies for Preparing Microneedles

• Wet Etching Technology

Wet etching is a technique in which the pattern of a mask plate is transferred to a photoresist, and the SiO₂ layer on the surface of the silicon wafer is used as a mask plate to etch the internal structure of the silicon wafer again to fabricate microneedle arrays by wet etching. The microneedles prepared by wet etching not only play an important role in medical monitoring and transdermal drug delivery, but also can be used to extract and collect fluids for minimally invasive diagnosis by piercing the dermis of human skin.

• Dry Etching Technology

Dry etching is a process that uses plasma to treat silicon wafers, which allows for high aspect ratio structures without the hazards of chemicals. The most used dry etching techniques are generally reactive techniques with chemical and physical effects, such as reactive ion etching (RIE) and deep reactive ion etching (DRIE). The microneedles prepared by dry etching can be used for drug delivery, glucose testing and cell transplantation in combination with some external access devices such as sensors, without chemical contamination.

Combination and Optimization of Etching Technologies

• Technology Combination

CD Formulation can combine dry etching technology and wet etching technology, which can solve the problem of depth to width ratio and strength of microneedles, thus maximizing the effect in practical applications. The combination of the two techniques allows the production of microneedle arrays of different shapes, materials and aspect ratios for different applications.

• Technology Optimization

1. Wet etching optimization

By varying the concentration of wet etching chemistry, etching time and temperature, the shape of the mask and the material of the substrate, the performance of the microneedles can be influenced to improve the strength of the microneedles while maintaining the same shape, which can be used for medical testing, transdermal drug delivery, blood collection and wearable patches.

2. Dry etching optimization

To enhance the strength and toughness of microneedles, the desired effect can be achieved by controlling the timing of deep reactive ion etching and atomic layer deposition during the preparation process. The process simplifies the fabrication process and the strength and toughness of the microneedles can be easily tuned by varying the deposition time of the film.

CD Formulation provides technical support and technical solutions for wet etching and dry etching to help customers with microneedle patch project development and product optimization. Based on our current technology and testing capabilities, we can provide you with a full range of product analysis and testing. If your project needs development and optimization, please contact us and we will customize our technical support and solutions exclusively for you.