【introduction】

Graphene has become a versatile material for making flexible electronic devices due to its excellent flexibility, transparency, electrical conductivity, and mechanical strength. In the past ten years, various laser technologies have been used for graphene processing, such as: laser reduced graphene oxide (LRGO), patterning of graphene, multi-stage structuring, heteroatom doping, delayering, and etching , Impact, etc., and laser-treated polyimide (PI) to prepare graphene (LIG). Graphene is widely used in the preparation of a variety of electronic devices, such as generators, supercapacitors, optoelectronic devices, sensors and drivers.

[Achievement Profile]

Recently, in particular, political academician Tsinghua University and Professor Zhang to Jilin University, Dr. Han Dongdong team (corresponding author) under the leadership of, and Peking University Ph.D. in particular Core (first author) cooperation, reviewed the progress of work flexible graphene electronics laser manufacturing base. This article summarizes a variety of laser processing technologies for the preparation, processing, and modification of graphene and its derivatives. An overview of various graphene flexible electronic devices based on typical lasers. A comprehensive review of the use of continuous and pulsed lasers to process GO, chemical vapor deposition (CVD) grown graphene, and laser-induced graphene. Discusses the various functions of laser-processed graphene, such as photoreduction of GO, maskless patterning, multi-level structure, reduction of CVD-grown graphene, etching, impact, and laser-made graphene on PI substrate. Laser processing of graphene has made great contributions to the development of graphene-based flexible electronic devices. Summarize the typical flexible electronic devices prepared by laser, such as: generators, super capacitors, sensors, optoelectronic devices, drivers and intelligent integrated devices. Finally, we look forward to the current challenges and future research directions. Related results were published on Advanced Materials under the title " Laser Fabrication of Graphene - Based Flexible Electronics " .

[Picture and text guide]

FIG 1 the laser processing graphene and derivatives thereof in the development of graphene-based flexible electronic device aspects of work progress

Figure 2 Laser reduction GO

a) Absorption spectrum of GO.

b) Schematic diagram of laser photochemical reduction of GO, AFM image, physical photo (scale bar: 1 mm).

c) C 1s XPS spectra of GO and LRGO.

d) SEM images of LRGO prepared by GO and laser photothermal reduction. Scale bar: 10 μm.

e) Resistance controlled LRGO.

Figure 3 Graphene grown by laser-treated CVD and laser-induced graphene

a) Schematic diagram of laser ablation graphene (left) and DFT model of graphene oxidation on gold film (right). On the right, O, C, and Au atoms are represented by red, brown, and gold balls, respectively.

b) Folding of graphene.

c) Laser shock of graphene.

d) Corresponding SEM and AFM images.

e) Schematic diagram of LIG preparation (left). Photo in kind (right).

f) HRTEM image of LIG. Scale bar: 5 nm.

g) Raman spectrum of LIG.

FIG 4 patterning of the graphene

a) LRGO-based spider web and Jilin University emblem design. Scale bar: 10 μm.

b) Taiji (scale bar: 50μm), panda (scale bar: 10μm) and graphene circuit patterns based on LRGO.

c) Three-dimensional pattern based on LRGO.

d) Laser-processed patterns of CVD graphene.

e) LIG-based patterning.

f) Three-dimensional shape based on LIG.

g) Three-dimensional shape of laser-processed CVD graphene.

FIG . 5 multilevel structure of graphene

a) SEM image of LRGO porous structure.

b) SEM image of LIG porous structure (left, scale: 10 μm; inset, scale: 1 μm) and TEM image (right, scale: 5 Å).

c) Schematic diagram of LRGO grating structure obtained by laser interference technology.

d, e) SEM images of 1D and 2D grating-like structures LRGO.

f) 1D and 2D grating structures LRGO are used for light diffraction demonstration.

g) Graphene with multi-stage structure prepared by CVD method.

h) Structural color of multi-stage graphene.

Figure 6 Heteroatom-doped graphene

a) Preparation of N-doped LRGO in NH ₃ atmosphere.

b) Device structure of N-doped LRGO as FETs channel.

c) XPS spectra of GO and N-doped LRGO.

d) Transfer characteristics of N-doped LRGO FETs.

e) Fluorinated graphene.

f) Performance comparison of graphene devices before and after fluorination.

Figure 7 Graphene generator

a) Schematic diagram of humidity-electric conversion device.

b, c) Performance curve of humidity-electric conversion device.

d) A writing board prepared using a humidity-electric conversion device.

e) Stretchable humidity-electric conversion device.

f) Schematic diagram of pressure generator.

g) Photo of the parallel pressure generator.

h) Short-circuit current curve.

Figure 8 Graphene supercapacitor

a, b) a) In-plane and b) Sandwich structure supercapacitors.

c) Schematic diagram and physical photos of the flexible LRGO supercapacitor device.

d) Performance test of LRGO supercapacitors with different bending angles.

e) Leakage current curves for supercapacitor-sensor integration and integrated devices.

f) Charge and discharge curve of the integrated device.

Figure 9 Graphene strain and pressure sensor

a) The relationship between the change in the relative resistance of the strain sensor and the tensile deformation.

b, c) b) frequency of the strain sensor and c) cyclic characteristics of 2% tensile.

dh) Strain sensors are used for d) finger bending, eg) breathing, and h) pulse detection.

ik) i) device structure of LRGO pressure sensor, j) sensing mechanism, k) relationship between conductance and pressure.

Figure 10 Graphene biosensor

a) Schematic diagram of monitoring EEG, ECG and EMG signals using LIG biosensors.

b) Photographs and SEM images of elastomer sponge substrates and LIG biosensors.

ce) c) alpha rhythm recorded by biosensor, d) ECG, e) EMG signal.

Figure 11 Graphene Transducer

a) Schematic diagram of the working principle of the ion driver.

b) Durability of IPGC and IPMC drivers with EMI-BF ₄ electrolyte.

c) Schematic diagram of the working principle of the electric heating driver.

d) Electrothermal bionic flytrap.

Figure 12 Graphene artificial throat

a) The working mechanism of artificial throat.

b) A physical photo of the artificial throat. Scale bar: 1 cm.

c) Artificial throat detection and conversion of weak vibrations.

df) sound signal: d) high volume 10 kHz, e) low volume 10 kHz, f) low volume 5 kHz.

[ Summary ]

Graphene has excellent flexibility, electrical conductivity, transparency, mechanical strength, and controllable electrical conductivity, and has become a multifunctional material for preparing flexible electronic devices. In the past ten years, the preparation, processing and application of graphene have been greatly developed, and the application of graphene materials in electronic devices has been promoted. In the development of flexible graphene-based electronic devices, laser manufacturing technology plays a very important role, such as: programmable pattern design, multi-level structure, device manufacturing and integration. Various graphene sources have been successfully used in laser processing, such as GO, CVD graphene, and LIG. Laser-reduced GO has the following advantages. First, maskless and chemically-free patterning can be achieved. Second, laser processing can produce micro-nano multi-level structures. Third, by adjusting the content of oxygen-containing functional groups, electrical performance is regulated. Fourth, laser reduction is used for heteroatom doping. Therefore, laser-reduced GO is a promising technology for manufacturing flexible electronic devices. For CVD graphene, laser ablation can be used for CVD graphene patterning. Laser thinning can precisely control the number of graphene layers. In addition, laser-assisted etching and impact can promote graphene modification and topography. Recently, LIG fabrication of PI substrates by laser irradiation has become a research hotspot of graphene-based flexible electronic devices. Using laser direct writing technology, any required graphene pattern can be directly prepared on a flexible PI substrate. The method is simple and low cost, and has been widely used in the development of a variety of flexible electronic devices. Through laser processing technology, a variety of graphene-based flexible electronic devices have been developed, such as generators, supercapacitors, optoelectronic devices, sensors and drivers.

Laser processing of graphene still has some limitations. Laser direct writing technology has low manufacturing efficiency. In practical applications, parallel processing methods can be adopted to solve the efficiency problem, such as using a spatial light modulator or holographic laser processing. For photoreduction of GO, laser treatment can remove most of the oxygen-containing functional groups and restore the conductivity of LRGO. However, during the severe deoxidation process, the sp ² carbon plane was destroyed, resulting in many defects. For LIG, compared to a single layer of smooth graphene, the formed LIG has a porous structure. Therefore, LIG is suitable for preparing sensors and supercapacitors, and is not suitable for use in photovoltaic devices such as OLEDs that require smooth electrodes. With the rapid development of laser processing technology and graphene preparation methods, more graphene-based electronic devices will be prepared by laser processing technology. With the continuous development of this field, laser-produced graphene electronic devices will have broad application prospects.

Literature link: Laser Fabrication of Graphene - Based Flexible Electronics(Adv. Mater., 2019, DOI: 10.1002 / adma.201901981)

Source of information: material cattle