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Printed electronics offer a breakthrough in the penetration of information technology into everyday life. The possibility of printing electronic circuits will further promote the spread of the Internet of Things applications. Inks based on graphene have a chance to dominate this technology, as they potentially can be low cost and applied directly on materials like textile and paper. Here we report the environmentally sustainable route of production of graphene ink suitable for screen-printing technology. The use of non-toxic solvent Dihydrolevoglucosenone (Cyrene) significantly speeds up and reduces the cost of the liquid phase exfoliation of graphite. Printing with our ink results in very high conductivity (7.13 × 10 4  S m −1 ) devices, which allows us to produce wireless connectivity antenna operational from MHz to tens of GHz, which can be used for wireless data communication and energy harvesting, which brings us very close to the ubiquitous use of printed graphene technology for such applications. Printed conductive inks show promise for future electronic device applications. Here, the authors report synthesis of graphene inks with conductivity of 7.13 × 10^4 S/m by Cyrene assisted liquid phase exfoliation, and their applications in data communication and RF energy harvesting.

Rapid synthesis of high-entropy alloy nanoparticles (HEA NPs) offers new opportunities to develop functional materials in widespread applications. Although some methods have successfully produced HEA NPs, these methods generally require rigorous conditions such as high pressure, high temperature, restricted atmosphere, and limited substrates, which impede practical viability. In this work, we report laser solid-phase synthesis of CrMnFeCoNi nanoparticles by laser irradiation of mixed metal precursors on a laser-induced graphene (LIG) support with a 3D porous structure. The CrMnFeCoNi nanoparticles are embraced by several graphene layers, forming graphene shell-encapsulated HEA nanoparticles. The mechanisms of the laser solid-phase synthesis of HEA NPs on LIG supports are investigated through theoretical simulation and experimental observations, in consideration of mixed metal precursor adsorption, thermal decomposition, reduction through electrons from laser-induced thermionic emission, and liquid beads splitting. The production rate reaches up to 30 g/h under the current laser setup. The laser-synthesized graphene shell-encapsulated CrMnFeCoNi NPs loaded on LIG-coated carbon paper are used directly as 3D binder-free integrated electrodes and exhibited excellent electrocatalytic activity towards oxygen evolution reaction with an overpotential of 293 mV at the current density of 10 mA/cm2 and exceptional stability over 428 h in alkaline media, outperforming the commercial RuO2 catalyst and the relevant catalysts reported by other methods. This work also demonstrates the versatility of this technique through the successful synthesis of CrMnFeCoNi oxide, sulfide, and phosphide nanoparticles.We demonstrate a simple and versatile method to synthesize graphene shell-encapsulated high-entropy alloy nanoparticles through laser irradiation of mixed metal precursors in solid-phase, offering excellent electrocatalytic activity and stability.

Conductive thin films are an essential component of many electronic devices. Measuring their conductivity accurately is necessary for quality control and process monitoring. We compare conductivity measurements on films for flexible electronics using three different techniques: four-point probe, microwave resonator and terahertz time-domain spectroscopy. Multiple samples were examined, facilitating the comparison of the three techniques. Sheet resistance values at DC, microwave and terahertz frequencies were obtained and were found to be in close agreement.

To prevent back wall damage in cavity workpieces during laser drilling, it is crucial to monitor hole penetration status in real time. This study proposes a laser drilling penetration monitoring method based on acoustic principles. First, the acoustic module parameters of the system were simulated and calibrated using COMSOL Multiphysics (version 6.1) software, resulting in an optimal sound source frequency of 35 kHz and an incident angle of 30° for the acoustic waves. Next, a nickel-based alloy laser drilling acoustic monitoring platform was designed and constructed, and the system’s upper computer control software was developed. Subsequent drilling trials were performed on the validated platform. During the experiments, the threshold for hole penetration signals under the specified experimental parameters was determined, enabling the acquisition of acoustic signals and the identification of hole penetration status. Furthermore, a correlation between the intensity of the acoustic signals and the exit aperture of the drilled holes was established. The results demonstrate the feasibility of using acoustic principles to monitor hole penetration status and measure machining aperture, providing both theoretical and experimental foundations for active laser drilling to prevent back wall damage.

A new metamaterial was demonstrated to absorb microwaves with 97.2%–97.7% absorption within a wide bandwidth of 1.56 GHz-18.3 GHz. The material has achieved the highest relative bandwidth and lowest thickness in the L to S-band reported so far. The design of multiple-layer metamaterial structures was for wide bandwidth microwave absorption. A one-step laser direct writing method was demonstrated to synthesize graphene and magnetic nanoparticles simultaneously. The laser direct writing enabled the achievement of an electrical sheet resistance from 57 to 480 Ω sq −1 with a 5% deviation. Microwave absorption in radar stealth technology is faced with challenges in terms of its effectiveness in low-frequency regions. Herein, we report a new laser-based method for producing an ultrawideband metamaterial-based microwave absorber with a highly uniform sheet resistance and negative magnetic permeability at resonant frequencies, which results in a wide bandwidth in the L- to S-band. Control of the electrical sheet resistance uniformity has been achieved with less than 5% deviation at 400 Ω sq −1 and 6% deviation at 120 Ω sq −1 , resulting in a microwave absorption coefficient between 97.2% and 97.7% within a 1.56–18.3 GHz bandwidth for incident angles of 0°–40°, and there is no need for providing energy or an electrical power source during the operation. Porous N- and S-doped turbostratic graphene 2D patterns with embedded magnetic nanoparticles were produced simultaneously on a polyethylene terephthalate substrate via laser direct writing. The proposed low-frequency, wideband, wide-incident-angle, and high-electromagnetic-absorption microwave absorber can potentially be used in aviation, electromagnetic interference (EMI) suppression, and 5G applications.

In this work, we have designed, fabricated and experimentally characterized a printed graphene nano-flakes enabled flexible and conformable wideband radar absorber. The absorber covers both X (8–12 GHz) and Ku (12–18 GHz) bands and is printed on flexible substrate using graphene nano-flakes conductive ink through stencil printing method. The measured results show that an effective absorption (above 90%) bandwidth spans from 10.4 GHz to 19.7 GHz, namely a 62% fraction bandwidth, with only 2 mm thickness. The flexibility of the printed graphene nano-flakes enables the absorber conformably bending and attaching to a metal cylinder. The radar cross section (RCS) of the cylinder with and without absorber attachment has been compared and excellent absorption has been obtained. Only 3.6% bandwidth reduction has been observed comparing to that of un-bended absorber. This work has demonstrated unambiguously that printed graphene can provide flexible and conformable wideband radar absorption, which extends the graphene’s application to practical RCS reductions.

School buses could alleviate the emissions associated with school travel. China is devoted to promoting its school bus service, leaving parents in a dynamic process of change from the original school travel mode to using the school bus service. This study analyzes parents’ switching intentions regarding school buses and decomposes the dimensions of certain critical factors by applying the Push–Pull–Mooring model. We conducted an online questionnaire survey of 463 parents. The measurement model result showed a satisfying prediction power, superior to that of existing theories. The results showed that perceived service quality is the most influential factor in the initial stage of school bus promotion. Among the four dimensions of perceived service quality, parents emphasize reliability and comfort. These results contribute to a deeper comprehension of parents’ intentions to switch to school bus services during the rollout phase and to ensuring sustainable school travel.

As graphene has been discovered since 2004, a large amount of papers investigating the fundamental physical and chemical properties of graphene has been published. However, the applications that perfect taking advantage of graphene’s properties are bare. This thesis focused on the development of graphene and graphene oxide (GO) based materials and their applications for electromagnetic ranges such as antennas, absorbers, wireless energy harvesting devices, sensors, and so on.In this thesis, physical exfoliation of graphene from graphite particles has been well discussed and compared. Both popular bath sonication and mechanical shear-mixing methods have been used and compared. The cost, concentration and conductivity of exfoliated graphene have been optimized. Moreover, the graphene based low-cost screen printing inks have been developed and discussed in this thesis. Excellent conductivity property allows engineers to produce wireless connectivity antenna operational from MHz to tens of GHz. Applications of printed, flexible Near Field Communication antenna (NFC), ultra high frequency Radio Frequency Identification (RFID) tags, wireless NFC sensors and ultra-wideband energy harvesting system have been designed, fabricated and demonstrated in this thesis.Due to the advances of ink preparation, cost and electrical properties, chemically exfoliated GO is used to replace physical exfoliated graphene on certain occasions. Printing and novel reduction process which can control reduced graphene oxide’s (rGO) conductivity has been demonstrated as well. The fabricated rGO laminate not only can be used in flexible electronic circuits as conductors or resistors but also highly efficient to absorb microwave radiations with proper design. A printed Jaumann structured microwave absorber has been characterized and compared with standard absorber which is consisted by graphene loaded composites.This thesis also presents the latest microfluidic RFID sensors for stretch sensing. The liquid, high conductive alloy based conductor has excellent sensitivity and repeatability comparing with lossy, rigid graphene based materials.

This chapter contains sections titled: Introduction Screen Printed Graphene Screen Printed Graphene for RFID Applications Chapter Summary

Defect detection is an emerging field in SHM, which not only reduces costs by minimizing maintenance and inspection cycles, but also prevents catastrophic failures at an earlier stage. As a non‐destructive evaluation method, the well‐known Lamb wave‐based defect detection and localization approach has been widely used in SHM. Due to its unique features of simplicity, durability, small size and low‐cost, piezoelectric lead zirconate titanate (PZT)‐based Lamb‐wave monitoring technology has shown great promise for defect detection in SHM. This chapter presents the basic principles of Lamb wave‐based defect detection and active PZT sensing. It introduces the newly developed wireless PZT sensor network for SHM, followed by the detailed design of the wireless PZT sensor nodes. The chapter discusses the procedure for distributed signal processing for SHM. The effectiveness and applicability of acoustic PZT monitoring were evaluated in both experimental and numerical investigations for three types of representative bridge: steel‐girder, reinforced concrete and pre‐stressed concrete.