Fig. 8.

a Schematic of a bioelectronic tongue developed using zinc oxide and graphene derivatives (rGO and GQDs) for monitoring of glucose present in saliva. Reprinted with permission from [241]. Copyright 2021 Elsevier. b Diagram of a graphene-based wearable contact lens sensor showing glucose sensing with graphene-AgNW. Reprinted with permission from [242]. Copyright 2017 Springer Nature. c The schematic picture of the graphene-based soft, smart contact lens for glucose detection. Reprinted with the permission from [243]. Copyright 2018 American Association for the Advancement of Science. d Schematic of the flexible graphene field-effect transistor (GFET) biosensor fabricated on an ultrathin film, and the device attached onto the artificial eyeball for detection of cytokine. Reprinted with the permission from [244]. Copyright 2020 Multidisciplinary Digital Publishing Institute. e Fabrication process and photographs of corneal microelectrode of corneal biosensors for the in vivo tears testing. Reprinted with the permission from [245]. Copyright 2020 Wiley–VCH. f Schematic illustration of integrated and therapeutic devices for chronic OSI. Reprinted with the permission from [246]. Copyright 2021 American Association for the Advancement of Science