The glass-PDMS-glass(G-P-G)sandwich microdevices provide some advantages over the whole-PDMS or PDMS-glass(P-G)hybrid microdevices,such as better mechanical properties,stronger reversible bonding and less evaporation [1].Especially their low evaporation expands the application of PDMS-based microfluidic devices to long-term experiments [2].However,current fabrication methods of the G-P-G microchip generally require a blade-assisted separation to release the rigid glass-PDMS hybrid from the master,which are apt to damage the fragile silicon master due to a strong bond between the rigid glass-PDMS and the silicon master,thus reducing the effectiveness of these methods.Here we present a novel strategy to fabricate G-P-G sandwich microdevices by using a water-dissolvable polyvinyl alcohol(PVA)film as a transfer carrier to handle the fragile structured PDMS film and then sandwiching it between two rigid glass substrates.This method can easily produce the G-P-G microdevices without any skills or special tools.Due to the high-barrier properties of the sandwiching glass plates,the G-P-G construction can control the evaporation rate of solutions in PDMS-based microdevices for meeting the requirements of long-term experiments.In order to demonstrate the capability of the G-P-G construction to suppress the evaporation of water,we compared the volume loss rate of droplets in the G-P-G microchip with that in the P-G microchip.In addition,we applied the G-P-G devices to protein crystallization experiments to further illustrate its low-evaporation power.