Sustained electron tunneling at unbiased metal-insulator-semiconductor triboelectric contacts

Liu, Jun,Miao, Mengmeng,Jiang, Keren,Khan, Faheem,Goswami, Ankur,McGee, Ryan,Li, Zhi,Nguyen, Lan,Hu, Zhiyu,Lee, Jungchul,Cadien, Ken,Thundat, Thomas Elsevier 2018 Nano energy Vol.48 No.-

<P><B>Abstract</B></P> <P>Generating sufficient current density for powering electronic devices remains as one of the critical challenges of mechanical energy harvesting techniques based on piezo and triboelectricity, mainly due to the high impedance of the insulating material systems. Here we report on producing sustainable tunneling current using an unbiased, triboelectrically charged metal-insulator-semiconductor (MIS) point contact system, consisting of p-type silicon, silicon oxide and a metal tip. The native thin oxide (~ 1.6 nm) on the silicon surface provides a natural pathway for quantum mechanical tunneling of the triboelectrically generated electrons into the silicon substrate. Lateral back and forth sliding motion of the tip, irrespective of the direction of motion, generates a constant direct current (d.c.) with very high current density. The measured current shows an exponential decay with the thickness of oxide layer deposited with atomic layer deposition (ALD), confirming the quantum mechanical tunneling mechanism. It is proposed that the contact potential difference enhanced by triboelectric charging provides potential difference between metal point contact and the substrate. With single metallic micro probe sliding on a moderately doped p-type silicon, an open circuit voltage (<I>V</I> <SUB>oc</SUB>) of 300–400 mV and a short-circuit direct current (<I>I</I> <SUB>sc</SUB>) of 3–5 μA (a corresponding high current density, <I>J</I>, in the order of 1–10 A/m<SUP>2</SUP>) have been observed. It is predicted from conductive-atomic force microscopy (C-AFM) experiment that the theoretical <I>J</I> can be as high as 10<SUP>4</SUP> A/m<SUP>2</SUP>. This new concept has the potential as a green energy harvesting technique where a broad range of material candidates and device configurations could be used.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Quantum mechanical tunneling at triboelectrically charged interface through ultrathin oxide layer is demonstrated. </LI> <LI> Tribo-tunneling is found to be a universal phenomenon in MIS frictional contact system. </LI> <LI> High current density <I>J</I> of 5 A/m<SUP>2</SUP> is experimentally measured in doped silicon materials at macroscale. </LI> <LI> Ultrahigh C-AFM <I>J</I> of 10<SUP>4</SUP> A/m<SUP>2</SUP> is observed due to the nano-size probe-induced high electric field. </LI> <LI> This method can be used as cost-effective triboelectric DC current generator, due to easily available silicon wafers with native oxide. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Tectono-magmatic evolution of the Mesozoic granodiorite and their diorite enclaves in Shulan Area, Jilin, China

Mengmeng Li,Jingdang Liu,Tianyi Liang,Chen Li,Dejun Bao 한국지질과학협의회 2022 Geosciences Journal Vol.26 No.1

The Mesozoic granodiorite and their diorite enclaves in the Shulan area have been investigated to understand the petrographic characteristics and elemental geochemistry and to further interpret the petrogenesis and paleotectonic environment. The petrography, mineral component, zircon U-Pb age, and major and trace element contents of 9 granodiorite host rock samples and 9 diorite enclave samples were analyzed. Results show host rock and the enclave both present of medium-fine subhedral and porphyritic. The main rock-forming minerals of host rocks are plagioclase (57–60%), quartz (25–30%), and K-feldspar (6–13%), whereas the main rock-forming minerals of enclaves are plagioclase (65–83%), amphibole (3–20%), and biotite (5–25%). Zircon U-Pb dating results show that the weighted-mean 206Pb/238U ages of the granodiorite host rock and the diorite enclave are 168.1 ± 1.6 Ma and 181.0 ± 1.0 Ma, respectively. The SiO2 contents of the host rocks and enclaves are 61.95–64.86% and 51.12–59.32%, respectively. Their K2O/Na2O ratios are 0.51–1.24 and 0.41–1.02; aluminum saturation index A/CNK [Al2O3/(CaO + Na2O + K2O) molar ratio] are between 0.80–1.14 and 0.70–0.98 and A/NK [Al2O3/(Na2O + K2O) molar ratio] are 1.48–1.97 and 1.47–2.11, indicating a medium-high-K calc-alkaline series and a metaluminous series. The chondrite-normalized rare earth element (REE) patterns of both host rock and enclave samples show a right-dip model, but the Eu ratios of the host rock samples show weak negative anomalies, whereas the Eu ratios of the enclave samples show distinctive negative anomalies. The δEu [δEu = EuN/sqrt(SmN × GdN)] averages of both host rock and enclave samples are 0.75 and 0.63, respectively. The primary mantle normalized trace element patterns shows the enrichment of Rb, Th, U, La, Zr, Hf and Li and the depletion of Nb and Sm in the granodiorite host rocks, whereas enriched Rb, U, La, Pr, Nd, Zr, Hf, and Li and depleting Ba, Nb, Sr, Sm, and Eu are presented in the diorite enclaves. The REE, trace element patterns and the other geochemical indices indicate both granodiorite and diorite were derived from partial melting of pre-existent basaltic materials with a minor contribution of mantle materials. Host rocks and enclaves were formed in the same subduction-related paleotectonic environment, but in different stages of magma evolution. The subduction triggered the delamination of the lithosphere, causing upwelling of the asthenosphere and partial melting of the crust, forming the magmatic precursors of both kinds of rocks.

Assessment of Myocardial Bridge by Cardiac CT: Intracoronary Transluminal Attenuation Gradient Derived from Diastolic Phase Predicts Systolic Compression

Mengmeng Yu,Yang Zhang,Yuehua Li,Minghua Li,Wenbin Li,Jiayin Zhang 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.4

Objective: To study the predictive value of transluminal attenuation gradient (TAG) derived from diastolic phase of coronary computed tomography angiography (CCTA) for identifying systolic compression of myocardial bridge (MB). Materials and Methods: Consecutive patients diagnosed with MB based on CCTA findings and without obstructive coronary artery disease were retrospectively enrolled. In total, 143 patients with 144 MBs were included in the study. Patients were classified into three groups: without systolic compression, with systolic compression < 50%, and with systolic compression ≥ 50%. TAG was defined as the linear regression coefficient between intraluminal attenuation in Hounsfield units (HU) and length from the vessel ostium. Other indices such as the length and depth of the MB were also recorded. Results: TAG was the lowest in MB patients with systolic compression ≥ 50% (-19.9 ± 8.7 HU/10 mm). Receiver operating characteristic curve analysis was performed to determine the optimal cutoff values for identifying systolic compression ≥ 50%. The result indicated an optimal cutoff value of TAG as -18.8 HU/10 mm (area under curve = 0.778, p < 0.001), which yielded higher sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy (54.1, 80.5, 72.8, and 75.0%, respectively). In addition, the TAG of MB with diastolic compression was significantly lower than the TAG of MB without diastolic compression (-21.4 ± 4.8 HU/10 mm vs. -12.7 ± 8 HU/10 mm, p < 0.001). Conclusion: TAG was a better predictor of MB with systolic compression ≥ 50%, compared to the length or depth of the MB. The TAG of MB with persistent diastolic compression was significantly lower than the TAG without diastolic compression.

Biomass Chitosan-Induced Fe3O4 Functionalized Halloysite Nanotube Composites: Preparation, Characterization and Flame-Retardant Performance

Mengmeng Zhang,Yamin Cheng,Zhiwei Li,Xiaohong Li,Laigui Yu,Zhijun Zhang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.15 No.01

An inorganic–organic nanohybrid flame retardant, HNT@CS@Fe3O4, is prepared by Halloysite nanotubes (HNT) as nanotemplate, chitosan (CS) as char-forming agent and ferroferric oxide (Fe3O4) playing in a catalytic role, aiming to endow enhanced flame-retardant performance of its nanohybrid. Results show that HNT@CS@Fe3O4 nanohybrids have a corn-like structure and can significantly improve the flame retardancy and thermal stability of epoxy resin (EP). Especially, the initial thermal degradation temperature of EP/HNT@CS@Fe3O4 is significantly improved by 24 ℃ relative to pure EP, and the residual carbon yield under air atmosphere is 8.8 wt.%, which is significantly higher than other EP composites, indicating a higher thermal stability is offered by the as-prepared nanohybrid. The limiting oxygen index of EP/10HNT@CS@Fe3O4 is 31.3%, which is 10.2% higher than that of pure EP. Meanwhile, the HNT@CS@Fe3O4 nanofiller reduces the peak heat release rate, CO production and peak smoke production release of EP nanocomposite by 32.0%, 44.0% and 33.0% in a cone calorimeter test, respectively. This is because the HNT-based composite can form a three-dimensional network structure into the EP matrix to inhibit heat release and diffusion of flammable moieties upon burning of EP. In the meantime, the incorporated Fe3O4 nanoparticle can in situ catalyze the charring of CS and EP matrix on the surface of HNT during the combustion process, which also contributes to the significantly increased fire safety of EP.

Calcification Remodeling Index Characterized by Cardiac CT as a Novel Parameter to Predict the Use of Rotational Atherectomy for Coronary Intervention of Lesions with Moderate to Severe Calcification

Mengmeng Yu,Yuehua Li,Wenbin Li,Zhigang Lu,Meng Wei,Jiayin Zhang 대한영상의학회 2017 Korean Journal of Radiology Vol.18 No.5

Objective: To assess the feasibility of calcification characterization by coronary computed tomography angiography (CCTA) to predict the use of rotational atherectomy (RA) for coronary intervention of lesions with moderate to severe calcification. Materials and Methods: Patients with calcified lesions treated by percutaneous coronary intervention (PCI) who underwent both CCTA and invasive coronary angiography were retrospectively included in this study. Calcification remodeling index was calculated as the ratio of the smallest vessel cross-sectional area of the lesion to the proximal reference luminal area. Other parameters such as calcium volume, regional Agatston score, calcification length, and involved calcium arc quadrant were also recorded. Results: A total of 223 patients with 241 calcified lesions were finally included. Lesions with RA tended to have larger calcium volume, higher regional Agatston score, more involved calcium arc quadrants, and significantly smaller calcification remodeling index than lesions without RA. Receiver operating characteristic curve analysis revealed that the best cutoff value of calcification remodeling index was 0.84 (area under curve = 0.847, p < 0.001). Calcification remodeling index ≤ 0.84 was the strongest independent predictor (odds ratio: 251.47, p < 0.001) for using RA. Conclusion: Calcification remodeling index was significantly correlated with the incidence of using RA to aid PCI. Calcification remodeling index ≤ 0.84 was the strongest independent predictor for using RA prior to stent implantation.

Unidirectional sensitive flexible sensor for bending measurements

Li Mengmeng,Liang Jiaming,Min Zhang 한국물리학회 2021 Current Applied Physics Vol.23 No.-

The measurement of bending direction and bending angles is essential in the multiaxial servo-controlled system, especially for collaborative robots. However, most flexible sensors developed for bending measurements cannot distinguish bending directions due to their sensitivity to both positive and negative bending. Also, these sensors usually exhibit simultaneous response to normal pressure, which results in additional calibration. Here, a unidirectional-sensitive flexible capacitive sensor is proposed. A simple asymmetric pyramidal microstructure was designed to create uneven responses to positive and negative bending and minimum response to normal pressure based on the fringe effect. The fabricated sensor shows a relative capacitance change of nearly 0.9 in the sensitive direction and only 0.05 in the other direction as the sensor bends from flat to the curvature radius of 10 mm. Also, the sensor shows negligible sensitivity even under a normal pressure force as high as 16 N, either in planar or bending condition.

Preparation and Investigation of Fe3O4@rGO/CNF Foams for Electromagnetic Interference Shielding

Mengmeng Li,Qiuyu Xu,Wei Jiang,Amjad Farooq,Yirui Qi,Lifang Liu 한국섬유공학회 2023 Fibers and polymers Vol.24 No.2

Herein, Fe3O4nanoparticles and graphene oxide (GO) are compounded first, followed by the addition of cellulose nanofiber(CNF) and l-ascorbic acid, to obtain Fe3O4@reduced graphene oxide (rGO)/CNF foams via the freeze-drying method. Theelectrical conductivity and magnetism of as-prepared foams were improved due to the presence of rGO and Fe3O4,whichis suitable for electromagnetic interference (EMI) shielding material. The results exhibit that Fe3O4@rGO/CNF foams allpossess a porous structure, and the optimized foam shows an EMI shielding effectiveness value of ~ 23 dB in the X-band. The good EMI shielding performance of the Fe3O4@rGO/CNF foam originates from the synergy of its composition andstructure. This work could provide a reference for the design and fabrication of novel EMI shielding materials.

Characterization of Volatile Compounds in Donkey Meat by Gas Chromatography–Ion Mobility Spectrometry (GC–IMS) Combined with Chemometrics

Mengmeng Li,Mengqi Sun,Wei Ren,Limin Man,Wenqiong Chai,Guiqin Liu,Mingxia Zhu,Changfa Wang 한국축산식품학회 2024 한국축산식품학회지 Vol.44 No.1

Volatile compounds (VOCs) are an important factor affecting meat quality. However, the characteristic VOCs in different parts of donkey meat remain unknown. Accordingly, this study represents a preliminary investigation of VOCs to differentiate between different cuts of donkey meat by using headspace–gas chromatography–ion mobility spectrometry (HS–GC–IMS) combined with chemometrics analysis. The results showed that the 31 VOCs identified in donkey meat, ketones, alcohols, aldehydes, and esters were the predominant categories. A total of 10 VOCs with relative odor activity values ≥1 were found to be characteristic of donkey meat, including pentanone, hexanal, nonanal, octanal, and 3-methylbutanal. The VOC profiles in different parts of donkey meat were well differentiated using three- and two-dimensional fingerprint maps. Nine differential VOCs that represent potential markers to discriminate different parts of donkey meat were identified by chemometrics analysis. These include 2-butanone, 2- pentanone, and 2-heptanone. Thus, the VOC profiles in donkey meat and specific VOCs in different parts of donkey meat were revealed by HS–GC–IMS combined with chemometrics, whcih provided a basis and method of investigating the characteristic VOCs and quality control of donkey meat.

Establishment and Application of a Femtosecond-laser Two-photon-polymerization Additive-manufacturing System

Shanggeng Li,Shuai Zhang,Mengmeng Xie,Jing Li,Ning Li,Qiang Yin,Zhibing He,Lin Zhang 한국광학회 2022 Current Optics and Photonics Vol.6 No.4

Two-photon-polymerization additive-manufacturing systems feature high resolution and precision. However, there are few reports on specific methods and possible problems concerning the use of small lasers to independently build such platforms. In this paper, a femtosecond-laser two-photon-polymerization additive-manufacturing system containing an optical unit, control unit, monitoring unit, and testing unit is built using a miniature femtosecond laser, with a detailed building process and corresponding control software that is developed independently. This system has integrated functions of light-spot detection, interface searching, micro-/nanomanufacturing, and performance testing. In addition, possible problems in the processes of platform establishment, resin preparation, and actual polymerization for two-photon-polymerization additive manufacturing are explained specifically, and the causes of these problems analyzed. Moreover, the impacts of different power levels and scanning speeds on the degree of polymerization are compared, and the influence of the magnification of the object lens on the linewidth is analyzed in detail. A qualitative analysis model is established, and the concepts of the threshold broadening and focus narrowing effects are proposed, with their influences and cooperative relation discussed. Besides, a linear structure with micrometer accuracy is manufactured at the millimeter scale.

A Performance Evaluation System for PPP Sewage Treatment Plants at the Operation-maintenance Stage

Xiaojuan Li,Yishu Liu,Mengmeng Li,Chi Yung Jim 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

Sewage treatment plants are essential in improving the quality of receiving water bodies, contributing to healthy and sustainable urban development. The increasingly common public-private partnership (PPP) model of sewage treatment facilities may not yield the expected benefits, often compromised by inadequacies in the complex operation-maintenance stage. Holistic criteria and methods to define and judge a plant’s performance are lacking. To fill the knowledge gap, this study established a performance evaluation system applicable to the critical operation-maintenance stage of China's PPP sewage-treatment industry. First, the range of quantitative and qualitative indicators was surveyed by literature review, and an appropriate subset was selected according to expert judgment. Second, the multilevel extension principle of matter-element analysis was combined with the analytic hierarchy process to determine the performance level and establish a comprehensive, efficient and practical evaluation system. The proposed method was tested on two PPP plants to confirm its applicability and reliability in assessing operation-maintenance functions. The study identified the diagnostic criteria to refine the design, operation and maintenance parameters to optimize plant performance. The findings provided an assured and comprehensive quality control scheme and a practical tool for governments and other parties to assess the service delivery quality of PPP plants.