D4 Scope (IMAGE) Duke University Caption The D4 assay is read by this battery-powered, tablet-sized scope, allowing the whole thing to be thrown into a backpack and be used at the point-of-care with minimal resources. Credit Jake Heggestad Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.