Design, Fabrication, and Efficacy of Customized Medical Masks

 Masks are a widely used and important device worn on the face to provide breathing  support such as oxygen or noninvasive ventilation (NIV), or to protect the wearer  from particulates. Two key features that define masks are that they are worn for  long periods of time, and they require a good fit to function properly; so, to be a  successful mask, it must be comfortable and well-fitting. Medical masks typically  come in generic sizes such as small, medium, and large, making it difficult for many  people to find a mask that fulfills these key requirements. This thesis focuses on two  masks: continuous positive airway pressure (CPAP) masks and N95 respirators. We  propose that medical mask efficacy, fit, and comfort can be improved by creating  custom-fit masks informed by the patient’s individual facial features and properties.  

In this thesis, we propose a mask customization technique based on the subject’s  facial anatomy. We have created a method to design and fabricate custom-fit CPAP  masks based on the subject’s facial contour. We use photogrammetry to collect the  patient’s facial contour, then use our own software to generate a 3D file of a silicone  interface layer based on the patient’s 3D face shape. We can then use finite element  analysis (FEA) to test the mask and potential leakage areas so we can make changes  before fabrication. N95 respirators are typically single-use devices and are better  suited to a rapid customization technique. We have developed a 3D printable mask  that, when paired with N95 filter material can serve as an N95 respirator replacement.  By exploiting the low melting temperature of PLA, these masks can be molded to  the user’s face with hot water, providing a good fit without having to try on several  masks.  

We have tested our mask-making methodology based on facial contour on CPAP  masks made in a five-person healthy subject study, where results suggest that the  iv Custom-Fit mask is more comfortable than the off-the-shelf version. The 3D-printed  moldable N95 masks have been quantitatively fit tested on 13 subjects with 77%  of subjects passing the fit test with the molded mask. We have shown that using  the proposed mask customization methodology produces comfortable and well-fitting  CPAP and N95 masks. Finally, we tested the custom-fit CPAP mask on a clinical  case study patient. This study provided many insights on how the mask performs  on someone who uses CPAP. Applying these methods to CPAP and N95 respirators  is only the beginning of what is possible, these methods could be applied to other  masks and other custom devices.