A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

Photo taken on March 26, 2020 shows a respirator made by using 3D priniting technology in Prague, the Czech Republic. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)

A developer demonstrates the process of making respirators by using 3D priniting technology in Prague, the Czech Republic, March 26, 2020. Facing the shortage of masks in the Czech Republic due to the spread of COVID-19, Czech Technical University in Prague developed a new type of respirator that can be produced by 3D printing technology. (Photo by Dana Kesnerova/Xinhua)