The First 3D-Printed Microneedle for Hearing Loss Treatment

The inner ear, especially the cochlea, remains one of the most challenging areas to address in medicine due to its intricate anatomy and limited accessibility. This presents significant hurdles in treating hearing loss (including hyperacusis) and other inner ear disorders. For more than a decade, a dedicated team of physicians and engineers at Columbia University has been working to overcome these challenges by developing a microneedle designed to enhance the delivery of medical treatments for hearing impairments. Additive manufacturing has been pivotal in creating this innovative device, enabling precise and efficient production.

Thanks to advancements in 3D printing, ENT surgeon Anil Lalwani and mechanical engineer Jeffrey Kysar have successfully developed an ultra-thin, 3D-printed microneedle for precision medicine in the inner ear. They believe this innovation could improve current therapies, particularly for previously inaccessible areas of the cochlea. The microneedle was created using two-photon photolithography, a specialized 3D printing technique that enables the production of high-resolution structures. This method ensures the needle is sharper than existing devices while remaining robust enough for practical use.

The microneedle can inject a contrast agent into the inner ear so that changes in the cochlea can be detected, helping to diagnose diseases such as Meniere’s disease. MRI images of the cochlea of a guinea pig show the different compartments of the cochlea. (Credit: Anil Lalwani/Columbia University Vagelos College of Physicians and Surgeons)

One difficulty is the cochlea’s complex anatomy. Dr. Lalwani explained that it is a spiral-shaped, fluid-filled bone: the hardest bone in our bodies. This makes it difficult to carry out therapies because to reach damaged cells, one has to go through a 2 mm wide, very delicate membrane, which often tears when using traditional instruments – a problem that can lead to hearing loss or even balance problems. The researchers needed to understand the factors that lead to tearing. For this reason, they envisioned the membrane as a tightly stretched tarp. If the hole is too large when inserted, the membrane tears. So, the width of the finished 3D-printed microneedle corresponds to the width of a human hair.

Therefore the main aim was to make it possible to treat the cochlea without damaging the membrane. In addition, the 3D-printed microneedle allows for fluid removal from the cochlea, which can help diagnose inner ear diseases such as Meniere’s disease, a localized disorder in the inner ear that leads to dizziness, nausea and hearing loss.

Numerous operations have already been performed on animals without negative effects or hearing loss, and the membrane healed within two days after each procedure. It is currently believed that the 3D-printed microneedle could fundamentally improve the treatment of the inner ear through precise surgery. Lalwani emphasizes: “It’s not an exaggeration to say our microneedle could be key to precision medicine for the inner ear.”

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*Cover Photo: Anil Lalwani/Columbia University Vagelos College of Physicians and Surgeons