November & December 2020
January & February 2021

Online event

Webinar 'Photonics in Healthcare'

Thursday 28 January
15:00 - 17:00

Rudolf Verdaasdonk

TechMed Centre, University of Twente

Title: The Myths about Mouth Masks unmasked: Real time air flow and droplet imaging to study effectiveness of personal protection in view of Covid-19 spreading


Visualization of air motion and droplets between persons will provide better insights to improve personal protection measures reducing the spreading of the Covid-19 virus. 

A unique Real-Time Background Oriented Schlieren (RT-BOS) technique has been developed to visualize the air motion during talking, coughing, sneezing, singing, playing wind instruments and the effectiveness using personal protection like face masks and shields. In addition, high speed backlight scatter imaging and fluorescent dyes were employed to visualize and quantify the spreading of droplets.     

The RT-BOS imaging shows that distance of air (aerosols) spreading depends on the diameter/shape of the opening and air volume blown out per unit of time. The shape of the mouth varies significantly between vowels and consequently the extent of spreading of both air and droplets. Remarkably, in contrast to ‘public perception’ the aerosol and droplet spreading of loud singing is similar or less than talking and wind instruments do not spread any droplets. Almost any covering of the mouth is effective in preventing droplets to spread. However, most face masks and shields (even the medical approved) leak air (aerosols) all around slowing down air motion to the front.  Air and droplet visualization techniques are very useful in validation studies for the effectiveness of personal protection measures in view of Covid-19 spreading and the images contribute to a better understanding and education of the general public. 


Rudolf M Verdaasdonk is full professor of Health Technology Implementation at the TechMed Center and staff member the Biomedical Photonics Imaging group at the University of Twente. Before, he was head and chair of the department of Physics and Medical Technology at the Amsterdam University Medical Center (VUmc). He received his MSc in Applied Physics at the Technical University Eindhoven in 1985 and his PhD in Medicine at the University Medical Center Utrecht in 1990. He has been working in University Medical Centers for over 30 years as a registered Clinical Physicist.

His research interest and expertise started with medical laser applications and expanded to a broad range of surgical equipment and imaging modalities. He has developed special imaging techniques for diagnostics and to study the interaction of equipment with the patient in view of safety, treatment quality and development of new applications. His advanced imaging facilities are being used for testing medical equipment of international companies. He is working in close collaboration with the clinical professionals and has practical experience in the OR assisting in surgery with complex technologies. He is active in patient safety, innovation and valorisation of new medical technology with several patents and devices being commercialized. He authored over 180 papers, proceedings and book chapters.

Company description:

The TechMed Centre of the University of Twente is an interfaculty Institute acting as a leading Innovation Hub impacting healthcare by excellent Research, Innovation and Educational programs. It is equipped with state-of-the-art infrastructure, ranging from research labs, preclinical testbeds and simulated hospital environments.