Scientists Put Masks to the Test—With a Cell Phone and a Laser

When it comes to blocking germs, not all cloth masks are created equal. A new, low-cost testing device literally illuminates which ones won’t get the job done.

Scientists Put Masks to the Test—With a Cell Phone and a Laser
When it comes to blocking germs, not all cloth masks are created equal. A new, low-cost testing device literally illuminates which ones won’t get the job done.