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Laser-Induced Graphene Based Flexible Electronic Devices

Herein, inspired by the tactile perception architecture of human skin, including the epidermis and touch receptor, skin-like flexible pressure sensors were fabricated via the assembly of a sandwich structure composed of an encapsulation layer (bionic epidermis), a piezoresistive sensing layer (bionic touch receptor), and a transducer layer. The piezoresistive sensing layer composed of graphene oxide/ hydroxyl functionalized carbon nanotubes/bovine serum albumin (GO/CNTs/BSA) nanocomposites with wavy microstructures was fabricated using layer-by-layer (LBL) self-assembly technology. The mechanisms of hydrogen bond and electrostatic interactions may improve the adhesion efficacy of the textile substrate with conductive nanomaterials. Based on the skin-like architecture for pressure sensing, the sensor exhibited the sensing characteristics, including wide pressure-detecting range (0∼171 kPa), high sensitivity (2.456 kPa−1), rapid response/recovery time (225 ms and 50 ms), and outstanding durability (2000 cycles). Our work provide references for textile-based electronic devices that can be applied to intelligent robotics, wearable monitoring, and man–machine interaction. 

Bioinspired sandwich-structured pressure sensors based on graphene oxide/hydroxyl functionalized carbon nanotubes/bovine serum albumin nanocomposites for wearable textile electronics

Flexible sensors are low cost, wearable, and lightweight, as well as having a simple structure as per the requirements of engineering applications. Furthermore, for many potential applications, such as human health monitoring, robotics, wearable electronics, and artificial intelligence, flexible sensors require high sensitivity and stretchability. Herein, this paper systematically summarizes the latest progress in the development of flexible sensors. The review briefly presents the state of the art in flexible sensors, including the materials involved, sensing mechanisms, manufacturing methods, and the latest development of flexible sensors in health monitoring and soft robotic applications. Moreover, this paper provides perspectives on the challenges in this field and the prospect of flexible sensors.

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Recent Advances in Flexible Sensors and Their Applications

Graphene has been regarded as a potential application material in the field of new energy conversion and storage because of its unique two-dimensional structure and excellent physical and chemical properties. However, traditional graphene preparation methods are complicated in-process and difficult to form patterned structures. In recent years, laser-induced graphene (LIG) technology has received a large amount of attention from scholars and has a wide range of applications in supercapacitors, batteries, sensors, air filters, water treatment, etc. In this paper, we summarized a variety of preparation methods for graphene. The effects of laser processing parameters, laser type, precursor materials, and process atmosphere on the properties of the prepared LIG were reviewed. Then, two strategies for large-scale production of LIG were briefly described. We also discussed the wide applications of LIG in the fields of signal sensing, environmental protection, and energy storage. Finally, we briefly outlined the future trends of this research direction.

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Research Progress on the Preparation and Applications of Laser-Induced Graphene Technology

Ca 2 LaSbO 6 : Mn 4+ , Eu 3+ phosphor has high sensitivity to temperature in the range of 273–473 ℃. • The Ca 2 LaSbO 6 : Mn 4+ , Eu 3+ phosphors were synthesized for the first time. • The sensing properties of Ca 2 LaSbO 6 : Mn 4+ , Eu 3+ showed its absolute sensitivity and relative sensitivity were 0.098 K −1 and 2.60% K −1 . • The material presents a good thermal stability. Optical temperature sensors based on photoluminescence materials have received considerable attention because of their noncontact measurement. However, such sensors still suffer from low sensitivity. Herein, A rationmetric optical temperature sensor with high sensitivity based on the spectra of Ca 2 LaSbO 6 : Mn 4+ , Eu 3+ (CLS: Mn 4+ , Eu 3+ ) phosphors was constructed. The temperature-dependent spectra were studied ranging from 273 to 473 K. Results showed that the fluorescence intensity of Mn 4+ ions attenuated faster than that of Eu 3+ ions with the increase of temperature because of their different thermal responses. Moreover, the sensing properties of CLS: Mn 4+ , Eu 3+ showed absolute sensitivity and relative sensitivity of 0.098 K −1 and 2.60% K −1 , respectively, based on the fluorescence intensity ratio of Mn 4+ and Eu 3+ . Therefore, CLS: Mn 4+ , Eu 3+ phosphor can be used for optical thermometry with high performance. 

Optical temperature sensor with superior sensitivity based on Ca2LaSbO6: Mn4+, Eu3+ phosphor

Facile fabrication of a fast-response flexible temperature sensor via laser reduced graphene oxide for contactless human-machine interface

To obtain a flexible dry bioelectrode with high performance, this paper proposes a flexible dry bioelectrode with microneedle structures inspired by golden margined century plant leaf. The microneedle structures are fabricated by laser processing method, and then embedded inside the flexible PDMS substrate. In this way, the flexible dry bioelectrode with curved-hook type microneedle structures is obtained. The mechanical and electrical properties of the bioelectrode are characterized. Our results show that the curved-hook type microneedle has a smaller penetration force (0.939 N) but bigger pullout force (0.149 N) compared with triangular microneedles. The curved-hook type microneedle structures allow better anti-destructive and bonding performance. Additionally, compared with traditional Ag/AgCl electrode, the developed flexible dry bioelectrodes exhibit better detection performance of EMG in both time and frequency domain.

Zheng Shen

Papers

Facile fabrication of a fast-response flexible temperature sensor via laser reduced graphene oxide for contactless human-machine interface

Fabrication and characteristic of flexible dry bioelectrodes with microstructures inspired by golden margined century plant leaf