Figures & data
Figure 1. Outline of surface engineering for enhancing performance of triboelectric energy harvesting devices. Reprinted with permission from [Citation77,Citation100,Citation108,Citation110,Citation120,Citation123,Citation124].
![Figure 1. Outline of surface engineering for enhancing performance of triboelectric energy harvesting devices. Reprinted with permission from [Citation77,Citation100,Citation108,Citation110,Citation120,Citation123,Citation124].](/cms/asset/c9fa998e-a0d8-4ad6-a756-2a863c68e825/tsta_a_1631716_f0001_oc.jpg)
Figure 2. (a) Schematic illustration and photograph of a simple-structured triboelectric energy harvester of the metal-to-insulator type in contact-separation mode. Equivalent circuits of the triboelectric energy harvesting system with an external load when the device is in (b) original, (c) pressed, and (d) released states, and (e) corresponding generated current signals during the single cycle. (f) Linear superposition tests of two triboelectric generators (G1 and G2) connected each other in parallel with same and opposite polarity. Reprinted with permission from [Citation90]. Copyright 2013 Elsevier.
![Figure 2. (a) Schematic illustration and photograph of a simple-structured triboelectric energy harvester of the metal-to-insulator type in contact-separation mode. Equivalent circuits of the triboelectric energy harvesting system with an external load when the device is in (b) original, (c) pressed, and (d) released states, and (e) corresponding generated current signals during the single cycle. (f) Linear superposition tests of two triboelectric generators (G1 and G2) connected each other in parallel with same and opposite polarity. Reprinted with permission from [Citation90]. Copyright 2013 Elsevier.](/cms/asset/aab958e8-5f6c-4c43-93a2-286b73b8fc62/tsta_a_1631716_f0002_oc.jpg)
Figure 3. (a) Schematics of the fabrication of laser-irradiated (LI) PDMS using ultrafast laser, and corresponding scanning electron microscopy (SEM) images of the LI-PDMS at laser power of 29 mW and 132 mW. Reprinted with permission from [Citation91]. Copyright 2017 Elsevier. (b) Schematics of the enlarged cross-sectional view of PEDOT:PSS/AgNW layer on a substrate (left). 3D topographic images of PEDOT:PSS, AgNW, and PEDOT:PSS/AgNW films (right). Reprinted with permission from [Citation66]. Copyright 2018 Elsevier. (c) Schematic illustration, photograph, and SEM image of the Au nanoparticles-coated surface based triboelectric generator. Reprinted with permission from [Citation75]. Copyright 2013 American Chemical Society.
![Figure 3. (a) Schematics of the fabrication of laser-irradiated (LI) PDMS using ultrafast laser, and corresponding scanning electron microscopy (SEM) images of the LI-PDMS at laser power of 29 mW and 132 mW. Reprinted with permission from [Citation91]. Copyright 2017 Elsevier. (b) Schematics of the enlarged cross-sectional view of PEDOT:PSS/AgNW layer on a substrate (left). 3D topographic images of PEDOT:PSS, AgNW, and PEDOT:PSS/AgNW films (right). Reprinted with permission from [Citation66]. Copyright 2018 Elsevier. (c) Schematic illustration, photograph, and SEM image of the Au nanoparticles-coated surface based triboelectric generator. Reprinted with permission from [Citation75]. Copyright 2013 American Chemical Society.](/cms/asset/5052d03a-dc24-407b-94ef-a3bd4dd3f02a/tsta_a_1631716_f0003_oc.jpg)
Figure 4. (a) Illustrated fabrication scheme of the nanopatterned surface of the block copolymer (BCP) TEG. The right panels show SEM images of BCP nanopatterned surface established by various self-assembly conditions. Reprinted with permission from [Citation77]. Copyright 2014 American Chemical Society. (b) Schematics of nanograting replication process onto a flexible plastic substrate using ultraviolet (UV)-curable resin. The right panel is the photograph of the wafer-scale and uniform nanograting replica onto the flexible plastic substrate. The inset is the SEM image of the ultra-long and defect-free nanograting pattern of the replica on the flexible substrate. Reprinted with permission from [Citation79]. Copyright 2017 Elsevier. (c) Schematics and SEM image of the interlocked TEG (i-TEG). Reprinted with permission from [Citation95]. Copyright 2016 Elsevier.
![Figure 4. (a) Illustrated fabrication scheme of the nanopatterned surface of the block copolymer (BCP) TEG. The right panels show SEM images of BCP nanopatterned surface established by various self-assembly conditions. Reprinted with permission from [Citation77]. Copyright 2014 American Chemical Society. (b) Schematics of nanograting replication process onto a flexible plastic substrate using ultraviolet (UV)-curable resin. The right panel is the photograph of the wafer-scale and uniform nanograting replica onto the flexible plastic substrate. The inset is the SEM image of the ultra-long and defect-free nanograting pattern of the replica on the flexible substrate. Reprinted with permission from [Citation79]. Copyright 2017 Elsevier. (c) Schematics and SEM image of the interlocked TEG (i-TEG). Reprinted with permission from [Citation95]. Copyright 2016 Elsevier.](/cms/asset/78b433a2-43e6-4f61-8dc4-c45950a4a29f/tsta_a_1631716_f0004_oc.jpg)
Figure 5. (a) The suggested mechanism of chemical elements and bonds of fresh, UV/O3, NaOH-, and HCl-treated PDMS surface. Reprinted with permission from [Citation100]. Copyright 2015 Elsevier. (b) Schematics of the surface functionalization with fluorinated organic materials on the PP nanowires. Bottom panels show the voltage generation and the charge density of PP-based TEGs before and after the diverse fluorinated modifications. Reprinted with permission from [Citation80]. Copyright 2016 Elsevier. (c) Current flow obtained from the triboelectric film of CNF, FEP, nitro-CNF, and methyl-CNF during a contact-separation cycle with Ga-In eutectic liquid (top). The scanning Kelvin probe microscopy (SKPM) surface potential mapping of pristine CNF, nitro-CNF, and methyl-CNF (bottom). Reprinted with permission from [Citation102]. Copyright 2017 John Wiley & Sons. (d) Schematics of the reactive ion etching (RIE) and the device fabrication processes of the S-TEG-CGG. Reprinted with permission from [Citation103]. Copyright 2017 American Chemical Society.
![Figure 5. (a) The suggested mechanism of chemical elements and bonds of fresh, UV/O3, NaOH-, and HCl-treated PDMS surface. Reprinted with permission from [Citation100]. Copyright 2015 Elsevier. (b) Schematics of the surface functionalization with fluorinated organic materials on the PP nanowires. Bottom panels show the voltage generation and the charge density of PP-based TEGs before and after the diverse fluorinated modifications. Reprinted with permission from [Citation80]. Copyright 2016 Elsevier. (c) Current flow obtained from the triboelectric film of CNF, FEP, nitro-CNF, and methyl-CNF during a contact-separation cycle with Ga-In eutectic liquid (top). The scanning Kelvin probe microscopy (SKPM) surface potential mapping of pristine CNF, nitro-CNF, and methyl-CNF (bottom). Reprinted with permission from [Citation102]. Copyright 2017 John Wiley & Sons. (d) Schematics of the reactive ion etching (RIE) and the device fabrication processes of the S-TEG-CGG. Reprinted with permission from [Citation103]. Copyright 2017 American Chemical Society.](/cms/asset/f189f2f1-487b-4571-9a99-a4a287acbdc7/tsta_a_1631716_f0005_oc.jpg)
Figure 6. (a) A step in the fabrication process of TEG devices for the thiol-SAM modified Au films. Bottom panels present the comparisons in the transferred charge density, generated voltage, and generated current density of each SAM functionalized TEGs. Reprinted with permission from [Citation82]. Copyright 2016 Royal Society of Chemistry. (b) Schematic illustrations of surface-functionalized polyethylene terephthalate (PET) substrates with various organic molecule head groups for negatively or positively charging. Reprinted with permission from [Citation104]. Copyright 2017 American Chemical Society. (c) Schematic diagram showing the propensity of the triboelectrification from electron-donating to electron-withdrawing layers according to the type of surface dipoles. Reprinted with permission from [Citation86]. Copyright 2016 American Chemical Society.
![Figure 6. (a) A step in the fabrication process of TEG devices for the thiol-SAM modified Au films. Bottom panels present the comparisons in the transferred charge density, generated voltage, and generated current density of each SAM functionalized TEGs. Reprinted with permission from [Citation82]. Copyright 2016 Royal Society of Chemistry. (b) Schematic illustrations of surface-functionalized polyethylene terephthalate (PET) substrates with various organic molecule head groups for negatively or positively charging. Reprinted with permission from [Citation104]. Copyright 2017 American Chemical Society. (c) Schematic diagram showing the propensity of the triboelectrification from electron-donating to electron-withdrawing layers according to the type of surface dipoles. Reprinted with permission from [Citation86]. Copyright 2016 American Chemical Society.](/cms/asset/9ac28e86-fd38-4022-ad2b-1212d3165b8b/tsta_a_1631716_f0006_oc.jpg)
Figure 7. (a) Fabrication illustration of the ionic molecule-injected fluorinated ethylene propylene (FEP) film and the final charge state of the FEP film for the contact-mode TEG. Reprinted with permission from [Citation81]. Copyright 2014 John Wiley & Sons. (b) Schemes of electron drift in the G-TEG device (left) and electron escape from PDMS to Au (right). Reprinted with permission from [Citation107]. Copyright 2018 American Chemical Society. (c) Schemes of PVDF/GO nanofibers presenting the dispersion of GO in the nanofiber (left) and stored charges on the surface of the GO sheet (right). Reprinted with permission from [Citation108]. Copyright 2015 Springer Nature. (d) Device design of the as-fabricated TEG improved by the hole transport layer (left) and the top-view and cross-sectional SEM images of the hole transport layer, showing ethylene glycol (EG)-PEDOT:PSS (EPP) layer coated PDMS surface (right and inset). Reprinted with permission from [Citation110]. Copyright 2016 American Chemical Society.
![Figure 7. (a) Fabrication illustration of the ionic molecule-injected fluorinated ethylene propylene (FEP) film and the final charge state of the FEP film for the contact-mode TEG. Reprinted with permission from [Citation81]. Copyright 2014 John Wiley & Sons. (b) Schemes of electron drift in the G-TEG device (left) and electron escape from PDMS to Au (right). Reprinted with permission from [Citation107]. Copyright 2018 American Chemical Society. (c) Schemes of PVDF/GO nanofibers presenting the dispersion of GO in the nanofiber (left) and stored charges on the surface of the GO sheet (right). Reprinted with permission from [Citation108]. Copyright 2015 Springer Nature. (d) Device design of the as-fabricated TEG improved by the hole transport layer (left) and the top-view and cross-sectional SEM images of the hole transport layer, showing ethylene glycol (EG)-PEDOT:PSS (EPP) layer coated PDMS surface (right and inset). Reprinted with permission from [Citation110]. Copyright 2016 American Chemical Society.](/cms/asset/788c1f91-e9d5-43ff-9b3e-14f05dca7de4/tsta_a_1631716_f0007_oc.jpg)
Figure 8. (a) Schematic illustrations of composite sponge PDMS-based TEG (CS-TEG) and its principle of performance enhancement. Reprinted with permission from [Citation65]. Copyright 2016 American Chemical Society. (b) Schematics and SEM image of the mesoporous PDMS film filled with Au nanoparticles (top). Triboelectric charge generation mechanisms of the Au NP-embedded mesoporous triboelectric nanogenerator and schematic energy band diagram (bottom). Reprinted with permission from [Citation118]. Copyright 2015 Royal Society of Chemistry. (c) Simple diagram of synthesis of PVDF-Gn graft copolymer for dielectric-controlled triboelectric energy harvesters (Top). The Kelvin probe force microscopy (KPFM) surface potential distribution images and work function values of pristine PVDF and PVDF-G18 films (bottom). Reprinted with permission from [Citation119]. Copyright 2017 AAAS. (d) Schematic description of the ferroelectric composite for control dielectric properties to enhance triboelectric energy harvesting. Reprinted with permission from [Citation120]. Copyright 2017 John Wiley & Sons. (e) Schematic illustrations of P(VDF-TrFE) solution in low dipole moment solvent and its corresponding film on a substrate (left), and P(VDF-TrFE) solution in high dipole moment solvent and its corresponding film on the substrate (right). Reprinted with permission from [Citation121]. Copyright 2017 John Wiley & Sons.
![Figure 8. (a) Schematic illustrations of composite sponge PDMS-based TEG (CS-TEG) and its principle of performance enhancement. Reprinted with permission from [Citation65]. Copyright 2016 American Chemical Society. (b) Schematics and SEM image of the mesoporous PDMS film filled with Au nanoparticles (top). Triboelectric charge generation mechanisms of the Au NP-embedded mesoporous triboelectric nanogenerator and schematic energy band diagram (bottom). Reprinted with permission from [Citation118]. Copyright 2015 Royal Society of Chemistry. (c) Simple diagram of synthesis of PVDF-Gn graft copolymer for dielectric-controlled triboelectric energy harvesters (Top). The Kelvin probe force microscopy (KPFM) surface potential distribution images and work function values of pristine PVDF and PVDF-G18 films (bottom). Reprinted with permission from [Citation119]. Copyright 2017 AAAS. (d) Schematic description of the ferroelectric composite for control dielectric properties to enhance triboelectric energy harvesting. Reprinted with permission from [Citation120]. Copyright 2017 John Wiley & Sons. (e) Schematic illustrations of P(VDF-TrFE) solution in low dipole moment solvent and its corresponding film on a substrate (left), and P(VDF-TrFE) solution in high dipole moment solvent and its corresponding film on the substrate (right). Reprinted with permission from [Citation121]. Copyright 2017 John Wiley & Sons.](/cms/asset/a360bf17-98bf-4286-8ed2-65115f10fa90/tsta_a_1631716_f0008_oc.jpg)
Figure 9. (a) Output current density generated by the Cu foil-grown 1L-, 2L-, 3L-, and 4L-stacked graphene-based TEG under same compressive force. Inset: a schematic illustration of graphene-based transparent TEG device with a spacer structure. Reprinted with permission from [Citation123]. Copyright 2014 John Wiley & Sons. (b) Schematics of MXene TEG (MXene/glass for the bottom electrode) with an air gap between top and bottom electrodes. ITO stands for indium tin oxide and PET for polyethylene terephthalate. Inset: illustration of Ti3C2Tx MXene structure. Reprinted with permission from [Citation124]. Copyright 2018 Elsevier. (c) Device structure of the TEG made by the MoS2 monolayer films (left). Schematics of the electron transfer from the PI matrix to the MoS2 monolayers (right). Reprinted with permission from [Citation125]. Copyright 2017 American Chemical Society.
![Figure 9. (a) Output current density generated by the Cu foil-grown 1L-, 2L-, 3L-, and 4L-stacked graphene-based TEG under same compressive force. Inset: a schematic illustration of graphene-based transparent TEG device with a spacer structure. Reprinted with permission from [Citation123]. Copyright 2014 John Wiley & Sons. (b) Schematics of MXene TEG (MXene/glass for the bottom electrode) with an air gap between top and bottom electrodes. ITO stands for indium tin oxide and PET for polyethylene terephthalate. Inset: illustration of Ti3C2Tx MXene structure. Reprinted with permission from [Citation124]. Copyright 2018 Elsevier. (c) Device structure of the TEG made by the MoS2 monolayer films (left). Schematics of the electron transfer from the PI matrix to the MoS2 monolayers (right). Reprinted with permission from [Citation125]. Copyright 2017 American Chemical Society.](/cms/asset/5ff3c20b-a9ca-42c3-a9b8-401587932d45/tsta_a_1631716_f0009_oc.jpg)
