Photo Credit: IANS IANSLive Singapore, June 9 (IANS) Scientists from Singapore's Nanyang Technological University (NTU) have developed a reusable "nanotech mask" that can block 99.9 per cent of bacteria, viruses and particulate matter (PM), as well as kill germs in just 45 seconds, much effective against Covid-19 than the currently used N95 masks.