A vat polymerization printer may comprise a tank assembly for containing a photo-curing liquid resin. The tank assembly may include a tank sidewall and a tank bottom formed by a membrane assembly. The membrane assembly may comprise a radiation-transparent flexible membrane and a frame affixed to a perimeter of the radiation-transparent flexible membrane. The radiation-transparent flexible membrane may include a radiation-transparent flexible substrate sandwiched between two fluorinated ethylene propylene (FEP) films or two polyolefin polymer films. More specifically, a first side of the radiation-transparent flexible substrate may be bonded to a first FEP or polyolefin polymer film, and a second side of the radiation-transparent flexible substrate may be bonded to a second FEP or polyolefin polymer film. In one embodiment, the radiation-transparent flexible substrate may be a layer of silicone rubber.