Structure‐Foldable and Performance‐Tailorable PI Paper‐Based Triboelectric Nanogenerators Processed and Controlled by Laser‐Induced Graphene

Abstract Laser‐induced graphene (LIG) technology has provided a new manufacturing strategy for the rapid and scalable assembling of triboelectric nanogenerators (TENG). However, current LIG‐based TENG commonly rely on polymer films, e.g., polyimide (PI) as both friction material and carbon precursor of electrodes, which limit the structural diversity and performance escalation due to its incapability of folding and creasing. Using specialized PI paper composed of randomly distributed PI fibers to substantially enhance its foldability, this work creates a new type of TENG, which are structurally foldable and stackable, and performance tailorable. First, by systematically investigating the laser power‐regulated performance of single‐unit TENG, the open‐circuit voltage can be effectively improved. By further exploiting the folding process, multiple TENG units can be assembled together to form multi‐layered structures to continuously expand the open‐circuit voltage from 5.3 to 34.4 V cm−2, as the increase of friction units from 1 to 16. Last, by fully utilizing the unique structure and performance, representative energy‐harvesting and smart‐sensing applications are demonstrated, including a smart shoe to recognize running motions and power LEDs, a smart leaf to power a thermometer by wind, a matrix sensor to recognize writing trajectories, as well as a smart glove to recognize different objects.

). High resolution N1s XPS spectrum of a LIG-1.25 W film and PI.The intensity of the N1s peak was greatly reduced after laser exposure (Figure S2b).High resolution O1s XPS spectrum of a LIG-1.25 W film and PI.After laser conversion, the C-O (531.2 eV) peak becomes more dominant than C=O (531.4 eV) (Figure S2c).The XRD pattern in the supporting information confirmed the existence of multilayer internal structure of graphene, and the strong peaks (002) and ( 100) were concentrated at 2θ = 26.3°and2θ = 43.5°,respectively (Figure S2d).
At each irradiation distance, the power parameters with the best voltage performance are 1.5, 1.25, 1.5, 1.75 and 2 W, respectively.Under these parameters, homogeneous porous layers are formed (Figure S3).The SEM images with different irradiation distances at 1.25 W power.Only at defocus distance 0 mm, a porous graphene layer is formed (Figure S4).Resistance changes at 0, 2, 4, and 6 hours under the durability test (Figure S5).
At the same time, SEM images and interface images of different times were also displayed, and after testing with different cycles, the graphene electrode remained basically intact (Figure S6).

Figure S1 .
Figure S1.The simulation diagram of the single-electrode TENG.

Figure S2 .
Figure S2.XPS pattern of C1s (a), O1s (b) and N1s (c) of the original PI and LIG-1.25(d) XRD pattern of LIG-1.25 and the original pi paper.High resolution C1s XPS spectrum of the LIG film and PI, showing the dominant C-C peak.The C-N, C-O and C=O peaks from PI were greatly reduced in the C1s XPS spectrum of LIG, which indicates that LIG was primarily sp 2 -carbons

Figure S6 .
Figure S6.SEM image of cross-section structure when the defocus distance is -1 mm and the power is 0.75 W, 1 W, 1.25 W, 1.5 W, 1.75 W, 2 W, 2.25 W.

Figure S7 .
Figure S7.SEM image of cross-section structure when the defocus distance is 1 mm, and the power is 0.75 W, 1 W, 1.25 W, 1.5 W, 1.75 W, 2 W, 2.25 W.

Figure S9 .
Figure S9.SEM image of cross-section structure when the defocus distance is 3 mm, and the power is 1 W, 1.25 W, 1.5 W, 1.75 W, 2 W, 2.25 W,2.5 W, 2.75 W.The laser induced graphene technology produces a tactile sensing system.The tactile sensor generated two, three, four and five finger signals when grasping the pen, box, keyboard and beaker, respectively.(FigureS10a-d).The performance of each unit of the matrix sensor is basically consistent, approximately 2 V.At the same time, the matrix sensor monitored the hand movements of writing BUAA.

Figure S10 .
Figure S10.Demonstration of the PIP-TENG in smart sensing.(a-d) The palm sensor generated two, three, four and five finger signals.

Figure S11 .
Figure S11.Demonstration of the PIP-TENG in smart sensing.(a) The voltage of each touch unit is basically the same (about 2 V).(b-d) Matrix sensors monitor writing movement.

Figure S13 .
Figure S13.TENG performance at different relative humidity levels.

Figure S14 .
Figure S14.The relationship between impact force and TENG performance.

Figure S15 .
Figure S15.(a) Resistance of LIG electrodes under different folding times.(b) The variation curve of resistance during the folding process.