Flexible and Highly Sensitive Piezoresistive Pressure Sensor with Sandpaper as a Mold

Wendan Jia,Qiang Zhang,Yongqiang Cheng,Dong Zhao,Yan Liu,Wendong Zhang,Shengbo Sang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.7

Flexible pressure sensors based on piezoresistive induction have recently become a research hotspot due to the simple device structure, low energy consumption, easy readout mechanism and excellent performance. For practical applications, flexible pressure sensors with both high sensitivity and low-cost mass production are highly desirable. Herein, this paper presents a high-sensitivity piezoresistive pressure sensor based on a micro-structured elastic electrode, which is low cost and can be mass-produced by a simple method of sandpaper molding. The microstructure of the electrode surface under external pressure causes a change in the effective contact area and the distance between the electrodes, which exhibits great pressure sensitivity. The test results show that the surface structure is twice as sensitive as the planar structure under low pressure conditions. This is because of the special morphology of silver nanowires (AgNWs), which exhibits the tip of nanostructures on the surface and realizes the quantum tunneling mechanism. The sensor has high sensitivity for transmitting signals in real time and it can also be used to detect various contact actions. The low cost mass production and high sensitivity of flexible pressure sensors pave the way for electronic skin, wearable healthcare monitors and contact inspection applications.

Fluorine-Substituted Dithienylbenzodiimide-Based n-Type Polymer Semiconductors for Organic Thin-Film Transistors

Feng, Kui,Zhang, Xianhe,Wu, Ziang,Shi, Yongqiang,Su, Mengyao,Yang, Kun,Wang, Yang,Sun, Huiliang,Min, Jie,Zhang, Yujie,Cheng, Xing,Woo, Han Young,Guo, Xugang American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.39

<P>Imide functionalization is one of the most effective approaches to develop electron-deficient building blocks for constructing n-type organic semiconductors. Driven by the attractive properties of imide-functionalized dithienylbenzodiimide (TBDI) and the promising device performance of TBDI-based polymers, a novel acceptor with increased electron affinity, fluorinated dithienylbenzodiimide (TFBDI), was designed with the hydrogen replaced by fluorine on the benzene core, and the synthetic challenges associated with this highly electron-deficient fluorinated imide building block are successfully overcome. TFBDI showed suppressed frontier molecular orbital energy levels as compared with TBDI. Copolymerizing this new electron-withdrawing TBDI with various donor co-units afforded a series of n-type polymer semiconductors TFBDI-T, TFBDI-Se, and TFBDI-BSe. All these TFBDI-based polymers exhibited a lower-lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analogue without fluorine. When applied in organic thin-film transistors, three polymers showed unipolar electron transport with large on-current/off-current ratios (<I>I</I><SUB>on</SUB>/<I>I</I><SUB>off</SUB>) of 10<SUP>5</SUP>-10<SUP>7</SUP>. Among them, the selenophene-based polymer TFBDI-Se with the deepest-positioned LUMO and optimal chain stacking exhibited the highest electron mobility of 0.30 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>. This result demonstrates that the new TFBDI is a highly attractive electron-deficient unit for enabling n-type polymer semiconductors, and the fluorination of imide-functionalized arenes offers an effective approach to develop more electron-deficient building blocks in organic electronics.</P> [FIG OMISSION]</BR>

3D Bioprinted GelMA/PEGDA Hybrid Scaffold for Establishing an In Vitro Model of Melanoma

( Jiahui Duan ),( Yanyan Cao ),( Zhizhong Shen ),( Yongqiang Cheng ),( Zhuwei Ma ),( Lijing Wang ),( Yating Zhang ),( Yuchuan An ),( Shengbo Sang ) 한국미생물생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.4

Due to the high incidence of malignant melanoma, the establishment of in vitro models that recapitulate the tumor microenvironment is of great biological and clinical importance for tumor treatment and drug research. In this study, 3D printing technology was used to prepare GelMA/PEGDA composite scaffolds that mimic the microenvironment of human malignant melanoma cell (A375) growth and construct in vitro melanoma micro-models. The GelMA/PEGDA hybrid scaffold was tested by the mechanical property, cell live/dead assay, cell proliferation assay, cytoskeleton staining and drug loading assay. The growth of tumor cells in two- and three-dimensional culture systems and the anti-cancer effect of luteolin were evaluated using the live/dead staining method and the Cell Counting Kit-8 (CCK-8) method. The results showed a high aggregation of tumor cells on the 3D scaffold, which was suitable for long-term culture. Cytoskeleton staining and immunofluorescent protein staining were used to evaluate the degree of differentiation of tumor cells under 2D and 3D culture systems. The results indicated that 3D bioprinted scaffolds were more suitable for tumor cell expansion and differentiation, and the tumor cells were more aggressive. In addition, luteolin was time- and dose-dependent on tumor cells, and tumor cells in the 3D culture system were more resistant to the drug.

ZnO/NiO nanofibers prepared by electrostatic spinning for rapid ammonia detection at room temperature

Shiqiang Xu,Junhe Wang,Hongying Lin,Rongchao Li,Yongqiang Cheng,Shengbo Sang,Kai Zhuo 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.6

ZnO/NiO heterojunction nanofibers were synthesized by an electrostatic spinning technique in thiswork. The morphologies, crystal structures, and compositional features of the ZnO/NiO nanofiberswere analyzed by SEM, TEM, XRD, and EDS characterization. ZnO/NiO nanofibers with Zn contentsof 37.5 at% showed a 46% response to 300-ppm ammonia gas at room temperature (25 ± 1 ℃;56 ± 3% RH), with fast response and recovery behavior (100 s /25 s). The existence of p-n heterojunctionson the surface of ZnO/NiO nanofibers, as well as surface ionic conduction, improved the responseto ammonia gas in a synergistic manner.

Enhanced mechanical properties and interface structure characterization of W-La₂O₃ alloy designed by an innovative combustion-based approach

Chen, Pengqi,Xu, Xian,Wei, Bangzheng,Chen, Jiayu,Qin, Yongqiang,Cheng, Jigui Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

Oxide dispersion strengthening (ODS) tungsten alloys are highly desirable in irradiation applications. However, how to improve the properties of ODS-tungsten alloys efficiently has been worth studying for a long time. Here we report a nanostructuring approach that achieves W-La₂O₃ alloy with a high level of flexural strength and Vickers hardness at room temperature, which have the maximum value of 581 MPa and 703 Hv, respectively. This method named solution combustion synthesis (SCS) can generate 30 nm coating structures W-La₂O₃ composite powders by using Keggin-type structural polyoxometalates as raw materials in a fast and low-cost process. The composite powder can be fabricated to W-La₂O₃ alloy with an optimal microstructure of submicrometric W grains coexisting with nanometric oxide particles in the grain interior, and a stability interface structure of grain boundaries (GBs) by forming transition zones. The method can be used to prepare new ODS alloys with excellent properties in the future.

Influences of weaving architectures and impact locations on the ballistic resistance of UHMWPE fabric

Zihan Zhu,Hu Zhou,Xiangshao Kong,Fang Liu,Yongqiang Zhang,Cheng Zheng,Weiguo Wu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

This study is devoted to reveal the influence of weaving architectures and impact locations on the ballistic resistance of UHMWPE (ultrahigh high molecular weight polyethylene) fabrics. Firstly, a mesoscopic model of UHMWPE fabric is established and the accuracy of the numerical method is verified. Subsequently, the models with different weaving architectures are further established, and the impact resistance performances are evaluated. Finally, the influence factors on the fabric ballistic resistance is explored. It is proved that the ballistic resistance of UHMWPE fabric mainly dominated by the tensile strength of yarn under highvelocity impact. The plain fabric shows best anti-ballistic performance, while basket and woven fabric are slightly inferior. The damage pattern of fabrics with different weaving architectures changes greatly. In addition, this study proposes a residual impact velocity correction model for projectile based on the probability distribution of impact positions, which can better characterize the protective ability of fiber fabrics.