還要「飲水思源」?

(http://www.bbc.com/news/science-environment-39482342) A UK-based team of researchers has created a graphene-based sieve capable of removing salt from seawater...The promising graphene oxide sieve could be highly efficient at filtering salts, and will now be tested against existing desalination membranes...But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapour deposition (CVD). Current production routes are also quite costly.