“…Recently, transparent paper made of CNs (NCC and NFC) had a representative thickness of 25-100 μm and a density of 0.8-1.5 g cm −3 , and attracted great attention because of its unique properties such as excellent flexibility [3,5,6,8,[89][90][91][92], superior surface smoothness [7,8,91], thermal stability [93,94], high optical transmittance [5,8,15,43,94,95], strong tensile strength [44,45,[47][48][49] and superior gas barrier performance in dry conditions [51-53, 87, 96-99]. These fascinating properties meet the stringent requirements of fabricating next generation 'green', transparent and flexible electronics on nanopaper.…”