Tian-Ling Ren

Tsinghua University, Peping, Beijing, China

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Publications (212)409.99 Total impact

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    ABSTRACT: A point Electrical Thermal Acoustic (ETA) device based on aluminum nanowire contacts is designed and fabricated. Interdigitated structural aluminum nanowires are released from the substrate by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). By releasing the interdigitated structure, the nanowires contact each other at approximately 1 mm above the wafer, forming a Point Contact Structure (PCS). It is found that the PCS acoustic device realizes high efficiency when a biased AC signal is applied. The PCS acoustic device reaches a sound pressure level as high as 67 dB at a distance of 1 cm with 74 mW AC input. The power spectrum is flat, ranging from 2 kHz to 20 kHz with a less than ±3 dB fluctuation. The highest normalized Sound Pressure Level (SPL) of the point contact structure acoustic device is 18 dB higher than the suspended aluminum wire acoustic device. Comparisons between the PCS acoustic device and the Suspended Aluminum Nanowire (SAN) acoustic device illustrate that the PCS acoustic device has a flatter power spectrum within the 20 kHz range, and enhances the SPL at a lower frequency. Enhancing the response at lower frequencies is extremely useful, which may enable earphone and loudspeaker applications within the frequency range of the human ear with the help of pulse density modulation.
    No preview · Article · Jan 2016 · Nanoscale
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    Li-Chuan Luo · De-Chun Bao · Wu-Qi Yu · Zhao-Hua Zhang · Tian-Ling Ren
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    ABSTRACT: It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180–400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.
    Preview · Article · Jan 2016 · Scientific Reports
  • Hao Ren · He Tian · Cameron Lee Gardner · Tian-Ling Ren · Junseok Chae
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    ABSTRACT: A microbial fuel cell (MFC) is a bio-inspired renewable energy converter which directly converts biomass into electricity. This is accomplished via the unique extracellular electron transfer (EET) of a specific species of microbe called the exoelectrogen. Many studies have attempted to improve the power density of MFCs, yet the reported power density is still nearly two orders of magnitude lower than other power sources/converters. Such low performance can primarily be attributed to two bottlenecks: i) ineffective electron transfer from microbes located far from the anode and ii) an insufficient buffer supply to the biofilm. This work takes a novel approach to mitigate these two bottlenecks by integrating a three-dimensional (3D) macroporous graphene scaffold anode in a miniaturized MFC. This implementation has delivered the highest power density reported of over 10,000 Wm-3 in all MFCs to date. The miniaturized configuration offers a high surface area to volume ratio and improved mass transfer of biomass and buffers. The 3D graphene macroporous scaffold warrants investigation due to its high specific surface area, high porosity, and excellent conductivity and biocompatibility which facilitates EET and alleviates acidification in the biofilm. Consequently, the 3D scaffold houses an extremely thick and dense biofilm from Geobacter-enriched culture, delivering an areal/volumetric current density of 15.51 Am-2 / 31,040 Am-3 and a power density of 5.61 Wm-2 / 11,220 Wm-3, a 3.3 fold increase when compared to the planar 2D control counterparts.
    No preview · Article · Jan 2016 · Nanoscale
  • Lu-Qi Tao · Ying Liu · He Tian · Zhen-Yi Ju · Qian-Yi Xie · Yi Yang · Tian-Ling Ren

    No preview · Article · Jan 2016 · AIP Advances
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    ABSTRACT: Organolead halide perovskites have attracted extensive attention as light harvesting materials for optoelectronic devices due to their high charge carrier mobility, high photoconversion efficiency, and long charge diffusion length. In this study, we present the first self-powered organolead halide perovskite single crystal photodetector driven by a triboelectric nanogenerator (TENG). A high-performance planar photodetector showing a responsivity of 7.92 A W1 to white light under a bias of 4 V was fabricated on the (100) facet of a bulk CH3NH3PbI3 perovskite single crystal. Furthermore, we demonstrate a cost-effective approach to the fabrication of a drum-shaped TENG by using two used digital versatile discs(DVDs), which could generate a high output of up to 200 V and 55uA. By integrating the CH3NH3PbI3 single crystal photodetector with the TENG, the self-powered device exhibited a large responsivity of 196 V (mW cm2)1 and a wide detection range from 10mWcm2to 100 mW cm2. These results provide a new strategy for driving the organolead halide perovskite photodetector with the energy harvested from the environment rather than an external power supply.
    Full-text · Article · Nov 2015 · Journal of Materials Chemistry C
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    Cheng Li · Ya-Long Cui · Gui-Li Tian · Yi Shu · Xue-Feng Wang · He Tian · Yi Yang · Fei Wei · Tian-Ling Ren
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    ABSTRACT: Motion capture is attracting more and more attention due to its potential wide applications in various fields. However, traditional methods for motion capture still have weakness such as high cost and space consuming. Based on these considerations, a flexible, highly stretchable strain sensor with high gauge factor for motion capture is fabricated with carbon nanotube (CNT) array double helices as the main building block. Ascribed to the unique flexible double helical CNT-array matrix, the strain sensor is able to measure strain up to 410%, with low hysteresis. Moreover, a demonstration of using this strain sensor for capture hand motion and to control a mechanical hand in real time is also achieved. A model based on finite difference method is also made to help understand the mechanism of the strain sensors. Our work demonstrates that strain sensors can measure very large strain while maintaining high sensitivity, and the motion capture based on this strain sensor is expected to be less expensive, more convenient and accessible.
    Full-text · Article · Nov 2015 · Scientific Reports
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    ABSTRACT: A highly sensitive sensor with piezoresistive nanocomposite material assembled in a flexible composite film is designed and tested for hydrodynamic sensing. Within the device, two nanocomposite films with micrometer scale modified small bumps on the surface are arranged together face-to-face by the interlocking mechanism. These structures are verified to have full-scale piezoresistive high sensitivities which are very appropriate for underwater sensing. Obvious output signals can be observed from the device subjected to the hydroacoustic dipole (vibrating sphere) with exciting frequency from 10Hz to 40Hz. A spectral peak can be seen in the Fourier analysis of the output signal at the corresponding frequency.
    No preview · Article · Nov 2015 · Chinese Physics Letters
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    ABSTRACT: Surface acoustic wave(SAW)transducers are a well-established component used in numerous sensors, communications, and electronics devices. In this work, the authors report a systematic study of 320–800 nm period lithium niobate SAWinterdigitated transducers(IDTs) corresponding to resonant frequencies in the 4–12 GHz range. An optimized SAW design and a nanofabrication process flow were developed, which enabled superior device performance in terms of frequency, signal losses, and electromagnetic coupling. The influence of the device alignment on the substrate crystal planes, in addition to the IDT period and electrode design, is found to have a significant impact on various process metrics. As an example, two identical SAW transducers fabricated perpendicular to each other may have a resonant frequency difference approaching 1 GHz, for the same harmonic mode. These and other trends are presented and discussed.
    No preview · Article · Nov 2015
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    ABSTRACT: The synaptic activities in nervous system is the basis of memory and learning behaviours, and the concept of biological synapses also spurred the development of neuromorphic engineering. In recent years, the hardware implementation of biological synapse has been achieved based on CMOS circuits, resistive switching memory and field effect transistors with ionic dielectrics. However, the artificial synapse with regulatable plasticity has never been realized in device level. Here, an artificial dynamic synapse based on twisted bilayer graphene is demonstrated with tunable plasticity. Due to the ambipolar conductance of graphene, both behaviours of the excitatory synapse and the inhibitory synapse could be realized in a single device. Moreover, the synaptic plasticity could also be modulated by tuning the carrier density of graphene. Since the artificial synapse here could be regulated and inverted via changing the bottom gate voltage, the whole process of synapse development could be imitated. Hence, this work would offer a broad new vista for the 2D material electronics, and guide the innovation of neuro-electronics fundamentally.
    No preview · Article · Oct 2015 · Nano Letters
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    ABSTRACT: A resistive random access memory (RRAM) device with a tunable switching window is demonstrated for the first time. The SET voltage can be continuously tuned from 0.27 to 4.5 V by electrical gating from -10 to +35 V. The gate-controlled bilayer graphene-electrode RRAM can function as 1D1R and potentially increase the RRAM density.
    Full-text · Article · Oct 2015 · Advanced Materials
  • Y. Gao · T. Ren · S.-X. Fu · Y.-M. Xiong · Y. Zhao
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    ABSTRACT: Laboratory tests have been conducted for flexible risers, here the aim was to further improve understanding the response performance of VIV of a long, flexible riser in water. The test was accomplished in a towing pool and the relative inflow was produced by towing the flexible riser in one direction. The displacements were obtained with the measured strain data based on the modal analysis method. The flexible riser in flow at different speeds was analyzed here, and its response parameters, such as, strain, characteristic frequency, non-dimensional displacement, lock-in region and fluid force coefficient were studied. The analysis results showed that the multi-order lock-in phenomena for VIV of a flexible riser appear with increase in flowing speed; vibration frequencies jump abruptly from one natural frequency to another in the high order lock-in region; the VIV response amplitude drops with increase in lock-in order. ©, 2015, Chinese Vibration Engineering Society. All right reserved.
    No preview · Article · Sep 2015 · Zhendong yu Chongji/Journal of Vibration and Shock
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    ABSTRACT: An atomic resolution ultra-high sensitivity surface acoustic wave (SAW) biosensor for DNA sequences and cells detection is proposed. Interdigitated transducers (IDTs) fabricated on LiNbO3 substrate achieve a high quality factor (Q) of over 4000 at a frequency of 6.4GHz (third-order harmonic mode) using an optimized design and process. The biosensor shows excellent linear responses to target DNA in the range from 1μg/ml to 1ng/ml with a high sensitivity of 6.7×10(-16)g/cm(2)/Hz, hence the difference of a single hybridized DNA base can also be distinguished. With such a high mass resolution, the biosensor is capable of quantitative detection of living cancer cells. The frequency responses of single mouse mammary adenocarcinoma (EMT6) cell and mouse fibroblast (3T3) cell are studied. The interferences in the experiments show insignificant influence on the frequency shift, which verifies the high selectivity of the biosensor. The biosensor is also able to repeat the sensing ability after rough cleaning, therefore cost reduction is achieved from the recycling process in practical applications. The detection limit is defined from the noise analysis of the device, atomic resolution is realized according to the calculation, thereby initiating a potential tool for high-precision medical diagnoses and phenomena observation at the atomic-level. Copyright © 2015. Published by Elsevier B.V.
    No preview · Article · Sep 2015 · Biosensors & Bioelectronics
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    ABSTRACT: We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 10(3). More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.
    Full-text · Article · Sep 2015 · Nanoscale
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    ABSTRACT: The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (∼450 nm) to red (∼750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-quality displays.
    Full-text · Article · Jul 2015 · Nature Communications
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    ABSTRACT: We report a potential way to effectively improve the magnetic properties of BiFeO3 (BFO) nanoparticles through Mg2+ ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.
    No preview · Article · Jun 2015 · Journal of Applied Physics
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    Yichao Tian · He Tian · Y L Wu · L L Zhu · L Q Tao · W Zhang · Y Shu · D Xie · Y Yang · Z Y Wei · X H Lu · Tian-Ling Ren · Chih-Kang Shih · Jimin Zhao
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    ABSTRACT: Many remarkable properties of graphene are derived from its large energy window for Dirac-like electronic states and have been explored for applications in electronics and photonics. In addition, strong electron-phonon interaction in graphene has led to efficient photo-thermo energy conversions, which has been harnessed for energy applications. By combining the wavelength independent absorption property and the efficient photo-thermo energy conversion, here we report a new type of applications in sound wave generation underlined by a photo-thermo-acoustic energy conversion mechanism. Most significantly, by utilizing ultrafast optical pulses, we demonstrate the ability to control the phase of sound waves generated by the photo-thermal-acoustic process. Our finding paves the way for new types of applications for graphene, such as remote non-contact speakers, optical-switching acoustic devices, etc.
    Full-text · Article · Jun 2015 · Scientific Reports
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    ABSTRACT: Toward a carbon neutral renewable energy conversion and storage device, we present a novel bio-inspired microbial supercapacitor, utilizing unique pseudocapacitance formed by exoelectrogen, a specific species of bacteria named Geobacter spp. grown on single-layer graphene film and 3D graphene-scaffold electrodes. Charging and discharging the microbial supercapacitor were performed by regulating the respiration of the exoelectrogen. Substantially high maximum current and power densities, 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked. The microbial supercapacitor demonstrates high cycle stability of over 1 million. A specific capacitance of 17.85±0.91 mF/cm2 is demonstrated, which is 4.4 fold to 2 orders of magnitude higher than previously reported supercapacitors having graphene-based electrodes, suggesting a promising alternative energy storage device. Furthermore, the microbial supercapacitor was used to deduce quantitative kinetic parameters of extracellular electron transfer (EET) by fitting discharging curves of the supercapacitor, which is critical to fully understand the EET of Geobacter spp. and determining the rate-limiting mechanism. At the initial-stage biofilm, the acetate turnover is the slowest among individual EET steps, whereas for fully-grown stage biofilm, kinetics of both acetate turnover and electron transfer from inside exoelectrogen to extracellular redox cofactors are rate-limiting. Our results also suggest cytochrome c may not be the main electron storage units of a microbial supercapacitor, regardless of initial- or fully-grown stage biofilms.
    No preview · Article · Jun 2015 · Nano Energy
  • Luqi Tao · Song Jiang · Cheng Li · He Tian · Ningqin Deng · Danyang Wang · Yi Yang · Tian-Ling Ren
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    ABSTRACT: Graphene-based materials have attracted much attention in recent years. Many researchers have demonstrated prototypes using graphene-based materials, but few specific applications have appeared. Graphene-based acoustic devices have become a popular topic. This paper describes a novel method to fabricate graphene-based earphones by laser scribing. The earphones have been used in wireless communication systems. A wireless communication system was built based on an ARM board. Voice from a mobile phone was transmitted to a graphene-based earphone. The output sound had a similar wave envelope to that of the input; some differences were introduced by the DC bias added to the driving circuit of the graphene-based earphone. The graphene-based earphone was demonstrated to have a great potential in wireless communication.
    No preview · Article · Jun 2015 · Tsinghua Science & Technology
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    ABSTRACT: We report a novel self-powered nanocomposite sensor composed of K0.5Na0.5NbO3 (KNN) nanoparticles (NPs) and multiwalled carbon nanotubes (MW-CNTs). The KNN NPs and MW-CNTs are dispersed in polydimethylsioxane by mechanical agitation to produce a piezoelectric nanocomposite device. The device exhibits an output voltage of approximately 30 V and output current of approximately 15 µA. Furthermore, the device exhibits potential as a self-powered pressure sensor because the output voltage can be tested to detect the pressure applied to the device and does not require other sources.
    Full-text · Article · Jun 2015 · Tsinghua Science & Technology
  • Changjian Zhou · Yi Shu · Yi Yang · Hao Jin · Shu-Rong Dong · Mansun Chan · Tian-Ling Ren
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    ABSTRACT: Flexible electronics have inspired many novel and very important applications in recent years and various flexible electronic devices such as diodes, transistors, circuits, sensors, and radiofrequency (RF) passive devices including antennas and inductors have been reported. However, the lack of a high-performance RF resonator is one of the key bottlenecks to implement flexible wireless electronics. In this study, for the first time, a novel ultra-flexible structured film bulk acoustic resonator (FBAR) is proposed. The flexible FBAR is fabricated on a flexible polyimide substrate using piezoelectric thin film aluminum nitride (AlN) for acoustic wave excitation. Both the shear wave and longitudinal wave can be excited under the surface interdigital electrodes configuration we proposed. In the case of the thickness extension mode, a flexible resonator with a working frequency as high as of 5.2325 GHz has been realized. The resonators stay fully functional under bending status and after repeated bending and re-flattening operations. This flexible high-frequency resonator will serve as a key building block for the future flexible wireless electronics, greatly expanding the application scope of flexible electronics.
    No preview · Article · May 2015 · Journal of Micromechanics and Microengineering