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Among his many theoretical insights, (https://www.livescience.com/albert-einstein.html) Albert Einstein predicted the existence of two phenomena in our universe that have since been proved: gravitational waves and the stimulated emission of radiation. [...]

Abstract Tissue paper softness relies on two major factors, the bulk softness, which can be indicated by the elasticity of the sheet, and surface softness. Measurement of surface softness is complicated and often requires a multi-step process. A key parameter defining surface softness is the topography of the surface, particularly the crepe structure and its periodicity. Herein, we present a novel approach to measure and quantify the tissue paper surface crepe structure and periodicity based on the detection of waviness along the sample using laser scanning confocal microscopy (LSM) and X-ray tomography (XRT). In addition, field emission scanning electron microscope (FESEM) was used to characterize the tissue paper surface. We demonstrate that surface topography is directly correlated to the erosion of the doctor blade, which is used to remove the dry tissue paper from the Yankee cylinder. Because of its accuracy and simplicity, the laser confocal microscopy method has the potential to be used directly on the production line to monitor the production process of the tissue paper. XRT revealed more structural details of the tissue paper structure in 3D, and it allowed for the reconstruction of the surface and the internal structure of the tissue paper. Graphic abstract

Laser-induced graphene (LIG) is a foam-like porous material consisting of few-layer graphene obtained by laser irradiation of a wide range of carbon-containing substrates. Among these, the ability to synthesize LIG from paper and other cellulose-related materials is particularly exciting, as it opens the door to a wide assortment of potential applications in the form of low-cost, flexible, and biodegradable devices. Here, the synthesis of this material, dubbed paper-LIG, on different types of filter papers and xylan biopolymer is discussed. In particular, we report the formation of paper-LIG by single-step irradiation, providing an improvement over the conventional multiple lasing approach and giving an explanation of the conditions that allow this simplified synthesis. All the relevant process parameters are covered, assessing their effect on the resulting electrical properties, structure, and morphology. Additionally, we demonstrate the application of LIG obtained from xylan, an abundant and often underutilized biopolymer, for temperature sensing. These results provide a better understanding of the conditions required for the synthesis of highly conductive LIG from paper and related materials, paving the way for its application, with reduced cost and low environmental impact, in fields ranging from biomonitoring to consumer electronics. published

This paper describes a method to fabricate microfluidic paper-based analytical devices (μPADs) using a toner laser printer. Multiple methods have been reported for the fabrication of μPADs for point-of-care diagnostics and environmental monitoring. Despite successful demonstrations, however, existing fabrication methods depend on particular printers, in-house instruments, and synthetic materials. In particular, recent discontinuation of the solid wax printer has made it difficult to fabricate μPADs with readily available instruments. Herein we reported the fabrication of μPADs using the most widely available type of printer: a toner laser printer. Heating of printed toner at 200 °C allowed the printed toner to reflow, and the spreading of the hydrophobic polymer through the filter paper was characterized. Using the developed μPADs, we conducted model colorimetric assays for glucose and bovine serum albumin (BSA). We found that heating of filter paper at 200 °C for 60 min caused the pyrolysis of cellulose in the paper. The pyrolysis resulted in the formation of aldehydes that could interfere with molecular assays involving redox reactions. To overcome this problem, we confirmed that the removal of the aldehyde could be readily achieved by washing the μPADs with aqueous bleach. Overall, the developed fabrication method should be compatible with most toner laser printers and will make μPADs accessible in resource-limited circumstances.

The recently emergent laser induced graphene paper (LIGP) has endowed the large-scale assembly of 2D electronics with freestanding and multifunctional natures. Liquid sensors, a crucial component in next-generation smart devices, were developed in this report through LIGP technology. Attributed to the one-step process of computer-aided laser scribing, the new sensor was fulfilled easily with arbitrary 2D shapes, sizes and array modalities. In comparison to indirect sensing manners existed majorly in polymer binder/substrate enabled carbon devices, the novel LIGP sensors with self-supported graphitic structures evidently showed multiple superiorities, including faster response, greater reproducibility, and higher sensitivity for micro-volume liquid detections. Benefiting from the laser-process dependent structures, we further proved the tunable sensing characteristics relying dominantly on specific surface area, a critical factor for introducing capillary pressure to facilitate liquid infiltration and electrical disruption. Additionally, a dual-mode liquid-recognition strategy based on both time and speed was creatively proposed for identification of various liquids. With successful utilization of 5 × 5 LIGP array for mapping the distribution of different fluid emissions on composite structures, we highly anticipate the escalation of LIGP sensors for commercialization, roll-to-roll manufacturing, and multimodal safety-assurance applications.

The graphene paper microsieves can be applied in the filtration of biological fluids or separation of solid particles from exploitation fluids. To produce graphene paper microsieves for specific applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 &micro, J, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (&ge, 10 &micro, m), optimum parameters of graphene paper laser ablation were defined using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre&ndash, Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of diffraction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.

Low-energy manufacturing of polymeric composites through two-dimensional electrothermal heaters is a promising strategy over the traditional autoclave and oven. Laser-induced graphene paper (LIGP) is a recent emergent multifunctional material with the merits of one-step computer aided design and manufacturing (CAD/CAM) as well as a flexible thin nature. To fully explore its capabilities of in situ heating, herein, we adventurously propose and investigate the customizable manufacture and modulation of LIGP enabled heaters with multimodally patternable performance. Developed by two modes (uniform and nonuniform) of laser processing, the LIGP heaters (LIGP-H) show distinctively unique characteristics, including high working range (>600 °C), fast stabilization (

The ability to synthesize laser-induced graphene (LIG) on cellulosic materials such as paper opens the door to a wide range of potential applications, from consumer electronics to biomonitoring. In this work, strain and bending sensors fabricated by irradiation of regular filter paper with a CO

We report a laser-based photo-polymerisation technique for the fabrication of 3D -multilayer paper-based devices. This method circumvents fabrication issues associated with other reported methods (e.g. alignment, contact), providing a pathway for mass-manufacture of paper-based devices.

We report the use of laser direct-writing for creation of size-exclusive, flow-through filters in paper-based devices. The usefulness of this novel filtration approach is demonstrated via an immunoassay that detects a common inflammation marker CRP.

A novel ratiometric fluorescent imprinted microfluidic device was constructed to rapidly detect trace pesticide residues. NBD-APTES was used as control fluorescence, and the fluorescence of carbon quantum dots modified with cysteine (CDs-Cys) was constructed to achieve rapid visual detection of the bacteriostatic agent difenoconazole. The analytical performance of paper-based chips was studied in detail using scanning electron microscopy and laser confocal microscopy. Under optimized conditions, the linear range of the fluorescence sensor is 0.3–60 μmol/L, the LOD is 75 nmol/L, the recoveries are 102.1%–111.2%, and the accuracy is 3.1%–4.2%. Compared with the traditional liquid phase fluorescence sensing materials, the ratiometric fluorescence sensor under the solid phase matrix has better portability and storability, showing satisfactory fluorescence characteristics. In addition, the sensor was highly specific for separating and detecting difenoconazole and was successfully applied to actual sample. It opens up new ways for the combination of ratiometric fluorescence technology and paper-based microfluidic chip, and provides potential point-of-care applications.

Graphene quantum dots (GQDs) are attractive fluorescent nanoparticles that have wide applicability, are inexpensive, nontoxic, photostable, water-dispersible, biocompatible and environmental-friendly. Various strategies for the synthesis of GQDs have been reported. However, simple and efficient methods of producing GQDs with control over the size of the GQDs, and hence their optical properties, are sorely needed. Herein, an ultra-fast and efficient laser writing technique is presented as a means to produce GQDs with homogeneous size from graphene produced by the instantaneous photothermal gasification and recrystallization mechanism. Controlling the laser scan speed and output power, the yield of GQDs can reach to be about 31.458 mg/s, which shows promising potential for large-scale production. The entire process eliminates the need for chemical solvents or any other reagents. Notably, the prepared laser writing produced GQDs (LWP-GQDs) exhibit blue fluorescence under UV irradiation of 365 nm and the Commission Internationale de L’Eclairage (CIE) chromaticity coordinates is measured at (0.1721, 0.123). Overall, this method exhibits superior advantages over the complex procedures and low yields required by other existing methods, and thus has great potential for the commercial applications.

Paper-based supercapacitors have attracted more and more attention for high electrochemical performance. However, most of them adopt sandwiched structure. Here, we prepared planar polypyrrole (PPy) coated paper-based supercapacitors by applying simple laser carving assisted method. The planar device showed a significant performance improvement (13.9 mF/cm2) compared to the sandwiched device (12.3 mF/cm2). In addition, by adjusting the polymerization time of pyrrole, the device capacity can be further increased to 87.4 mF/cm2. We firmly believed that the laser carving assisted method has a significant role in promoting the development of flexible planar electronic devices.

Development of paper-based sensors that do not suffer with humidity interference is desirable for practical environmental applications. In this work, a laser processing method was reported to effectively modulate the cross-sensitivity to humidity of ZnO-based UV (Ultraviolet) sensors printed on paper substrate. The results reveal that the laser induced zinc oxide (ZnO) surface morphology contributes to the super-hydrophobicity of the printed ZnO nanoparticles, reducing humidity interference while enhancing UV sensitivity. Herein, this conducted research highlights for the first time that laser processing is an attractive choice that reduces the cross-sensitivity to water vapor in the UV sensing response of ZnO-based devices printed on paper, paving the way to low-cost and sophisticated paper-based sensors.