(W1130-07-41) Comparison of Centrifugation Method and Vacuum Method in Fabricating Microneedles

Purpose: Centrifugation is the most commonly employed in fabricating molded polymer microneedles. However, it results in significant loss of the polymer solution during centrifugation. The purpose of this study was to investigate a vacuum method in fabricating the polymer microneedles and compare that to the microneedles made from centrifugation method.

Methods: The polymer solution was made with sodium alginate, chitosan base, and water. For making microneedles with centrifugation method, the polymer solution was placed in the microneedle mold, a spatula was used to even out the solution in the molds, any excess solution was removed, and then the mold was then placed in the centrifuge buckets at 4000 RPM for 15 minute. For making microneedles with vacuum method, the polymer solution was placed in the mold, a spatula was used to even out the solution in the molds, the molds were then placed in the vacuum oven with pressure decreased to 30 mmHg for 5 minutes, the molds were then taken out of the vacuum and any air bubbles that were present in the mold were removed with a spatula, additional solution was added to the molds. They were placed in the vacuum again at 30 mmHg for another 5 minutes, one again the air bubbles were removed and more solution was added to the molds. For both method, the molds were placed in the oven to dry overnight at 27 °C. Pictures were taken of the microneedles using stereomicroscope. Then 4 different weights: 10 grams, 20 grams, 50 grams, and 100 grams, were gently placed on top of the microneedles for 5 minutes. Then pictures were taken again for those microneedles. The heights of the microneedles were taken before and after the weights to assess their strength.

Results: The centrifugation method resulted in longer microneedles with a thinner platform that could easily be fractured. The thin platform was due to some of the polymer solution being lost during the centrifugation. In contrast, the vacuum method resulted in shorter needles with a sturdy platform. Since there was no loss of any polymer solution with the vacuum method, it resulted in a more durable base. However, unlike the centrifugation method, the microneedles were shorter with the vacuum method since there was no strong force pulling the solution into the microneedle mold. To further assess the difference in the two methods, different weights were placed slowly on the microneedles for five minutes to measure their strength. The microneedles made using the centrifuge method resulted in a higher percentage of loss of height with each weight compared to the microneedles made using the vacuum method implying that the microneedles from the vacuum method are stronger.

Conclusion: Vacuum method can be used to make molded polymer microneedles. The microneedles constructed using the vacuum method seemed stronger than the ones made using the centrifugation method.


Images of microneedles made using both centrifugation and vacuum methods before and after placing the weights.


Table summarizing the experiment results.