Laser-Induced Graphene from Commercial Inks and Dyes

Abstract

Laser-induced graphene (LIG) has been so far obtained from polymer precursors and proposed for numerous applications, including various types of sensors and energy storage solutions. This study examines a radically different class of new precursors for LIG, distinct from polymers: inks and dyes. The identification of specific organic dyes present in commercial markers demonstrates that the aromatic structure, in conjunction with high thermal stability (residual weight > 20% at 800°C), are key factors for laser-induced pyrolysis. Eosin Y is identified as an excellent LIG precursor, comparable with well-known polyimide. The unique properties of dyes allow for dispersion in various media, such as acrylic binder. A dye concentration of 0.75 mol L^-1 in acrylic binder results in a conductivity of 34 ± 20 S cm^-1 for LIG. The composition and microstructure of LIG from dyes are thoroughly characterized, revealing peculiar features. A versatile "Paint & Scribe" methodology is introduced, enabling to integrate LIG tracks onto any wettable surface, and in particular onto printed and flexible electronics. A process for obtaining freestanding and transferrable LIG is demonstrated by dissolving acrylic paint in acetone and floating LIG in water. This advancement offers novel avenues for diverse applications that necessitate a transfer process of LIG.

Keywords: Eosin Y; dye; freestanding; ink; laser‐induced graphene; pyrolysis; transfer.

Figure 1

Investigation of non‐permanent pen markers and dye identification. a) Image of areas of acrylic glass colored with various Lumocolor markers irradiated with an IR laser showing carbonization and/or ablation, b) FTIR of Lumocolor markers (dashed line = IR laser sources wavenumber); c) schematic of continuous defocus d screening with a 10° wedge; d) images of areas of glass slides coated with a film of the identified dyes and polyimide (considered as a standard reference polymeric precursor of LIG) showing ablation and/or carbonization at different levels of defocus (inset: chemical structures of dyes and polyimide).

Figure 2

Investigation of selected xanthene dyes for laser‐induced pyrolysis. a) Images of films of selected xanthene dyes showing ablation and carbonization at different levels of defocus d (inset: chemical structure of xanthene dyes). b) TGA of selected dyes in air and nitrogen environment showing different weight losses.

Figure 3

Characterization of LIG from Eosin Y films obtained from dye solutions at maximum concentration M6 and scribed with IR laser at P = 5% (top), 10% (middle), and 20% (bottom). a) Sheet resistance as a function of defocus with insets showing the corresponding optical images of the scribed samples. In b) average Raman spectra with standard deviations (shaded areas) and c) SEM images of the samples showing the lowest sheet resistance, marked in black in a).

Figure 4

Detailed characterization of LIG from M6P10D2.1. a) High magnification SEM images showing bright spots on the porous carbon structure, b) EDX, c) XPS, d) XRD showing characteristic peaks of NaBr crystals (PDF#15‐0010).^{[ 60 ]}

Figure 5

Characterization of LIG from Eosin Y/Acrylic binder films obtained from dye dispersion at two different concentrations AH2, AH3, upon IR laser scribing at P = 10, 20%. a) sheet resistance as a function of defocus. Marked samples in black, representing the lowest sheet resistance per each series, are further investigated with b) average Raman spectra, c) SEM images.

Figure 6

Detailed characterization of LIG from AH3P20D3.6. a) High magnification SEM images showing bright spots on the porous carbon structure, b) EDX, c) XPS, d) XRD of showing characteristic peaks of NaBr crystals (PDF#15‐0010).^{[ 60 ]}

Figure 7

a) Schematic illustration of the “Paint & Scribe” methodology on a generic object (mug) with an optional step of removing the paint by washing. b) Change of resistance (R/R0) of the LIG thermistor when hot water is poured into the mug; inset: image of the painted and scribed mug (scale bar = 10 mm) c) Thermal camera images of the mug filled with cold water (1), being filled with hot water (2) and the heated mug (3) d) Schematic illustration of the methodology for integration of “Paint & Scribe” with printed and flexible electronics showing the two approaches, “Paint, Scribe and Print” (PSP) and “Print, Paint, and Scribe” (PPS). e) Images of the PSP variant to integrate LIG with printed silver tracks on a PET foil substrate (scale bar = 5 mm), showing the painting with a marker (i), laser scribing (ii), washing away the ink in water (iii), printing of silver tracks (iv), flexing of the sample (v) and electrical connection (vi).

Figure 8

a) Schematic showing the creation and transfer of free‐standing LIG from an Eosin Y/acrylic binder precursor (detailed description in text). b) Pictures of LIG alphabet soup demonstrating the lift‐off transfer of free‐standing LIG from acrylic paint creating the anagram of EOSIN “NOISE”. c) Thermistor from free‐standing LIG transferred onto a glass slide heated to 80°C and cooled down to room temperature. d) Stretchable conductor made from free‐standing LIG transferred and embedded in PDMS.