Tian-Ling Ren

Tsinghua University, Peping, Beijing, China

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Publications (188)326.84 Total impact

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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.
    Biosensors & Bioelectronics 09/2015; 71. DOI:10.1016/j.bios.2015.04.043 · 6.45 Impact Factor
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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.
    Journal of Applied Physics 06/2015; 117(22):224101. DOI:10.1063/1.4922167 · 2.19 Impact Factor
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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.
    Scientific Reports 06/2015; 5:10582. DOI:10.1038/srep10582 · 5.58 Impact Factor
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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.
    Nano Energy 06/2015; DOI:10.1016/j.nanoen.2015.05.030 · 10.21 Impact Factor
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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.
    Tsinghua Science & Technology 06/2015; 20(3):264-269.
  • 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.
    Journal of Micromechanics and Microengineering 05/2015; 25(5). DOI:10.1088/0960-1317/25/5/055003 · 1.73 Impact Factor
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    ABSTRACT: Flexible pressure sensors working in the low pressure range (<10 kPa) becomes essential an important part of recent research for their applications in “artificial skin”, foldable electronics and so on. Several efforts have been focused on high sensitivity of the devices with the neglect of linearity which is essential for real applications. Here, we present a device with new Gauss random distribution contact surface profile and novel contact & piezoresistive composite working principle by numerical simulation which predicts the combination of wide linearity and high sensitivity. With the modified surfaces’ contact effect and piezoresistive capability of these nanocomposite structures, outstanding linearity can be achieved in full measurement measuring scale from 0 to 14KPa 14 kPa with high sensitivity around 13.8KPa-113.8 kPa-1. The random distribution surface also makes the device with fine stability and reproducibility which are validated in test.
    Nanoscale 04/2015; 7(18). DOI:10.1039/C5NR01259G · 7.39 Impact Factor
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    ABSTRACT: Pressure sensors are a key component in electronic skin (e-skin) sensing systems. Most reported resistive pressure sensors have a high sensitivity at low pressures (<5 kPa) to enable ultra-sensitive detection. However, the sensitivity drops significantly at high pressures (>5 kPa), which is inadequate for practical applications. For example, actions like a gentle touch and object manipulation have pressures below 10 kPa, and 10-100 kPa, respectively. Maintaining a high sensitivity in a wide pressure range is in great demand. Here, a flexible, wide range and ultra-sensitive resistive pressure sensor with a foam-like structure based on laser-scribed graphene (LSG) is demonstrated. Benefitting from the large spacing between graphene layers and the unique v-shaped microstructure of the LSG, the sensitivity of the pressure sensor is as high as 0.96 kPa(-1) in a wide pressure range (0 ~ 50 kPa). Considering both sensitivity and pressure sensing range, the pressure sensor developed in this work is the best among all reported pressure sensors to date. A model of the LSG pressure sensor is also established, which agrees well with the experimental results. This work indicates that laser scribed flexible graphene pressure sensors could be widely used for artificial e-skin, medical-sensing, bio-sensing and many other areas.
    Scientific Reports 02/2015; 5:8603. DOI:10.1038/srep08603 · 5.58 Impact Factor
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    ABSTRACT: Graphene is flexible and transparent with one-atom layer thickness, and is a novel building block with potential applications in future portable devices. Herein a flexible, transparent and ultrathin earphone based on single-layer graphene (SLG) is reported. The SLG earphone operates in the frequency range of 20 Hz to 200 kHz and has a highest sound pressure level (SPL) of 70 dB at a 1 cm distance. The SPLs emitted from one to six layers of stacked SLG are compared. It is observed that the SPL decreases with an increasing number of stacked layers. The SLG earphone, which is packaged with a commercial earphone casing, can play music clearly. Compared with a conventional earphone, the SLG earphone has a broader frequency response and a lower fluctuation. Testing results in both time and frequency domains show a frequency doubling effect, which indicates that the working principle is based on the electro-thermoacoustic (ETA) effect. As the SLG earphone operates in both the audible and ultrasonic frequency range, it can be used for a wide variety of applications.
    RSC Advances 02/2015; 5(22). DOI:10.1039/C4RA16047A · 3.84 Impact Factor
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    Yi Shu · Cheng Li · Zhe Wang · Wentian Mi · Yuxing Li · Tian-Ling Ren
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    ABSTRACT: Heart rate measurement is a basic and important issue for either medical diagnosis or daily health monitoring. In this work great efforts have been focused on realizing a portable, comfortable and low cost solution for long-term domestic heart rate monitoring. A tiny but efficient measurement system composed of a polymer-based flexible pressure sensor and an analog anti-interference readout circuit is proposed; manufactured and tested. The proposed polymer-based pressure sensor has a linear response and high sensitivity of 13.4 kPa-1. With the circuit's outstanding capability in removing interference caused by body movement and the highly sensitive flexible sensor device, comfortable long-term heart rate monitoring becomes more realistic. Comparative tests prove that the proposed system has equivalent capability (accuracy: <3%) in heart rate measurement to the commercial product.
    Sensors 02/2015; 15(2):3224-35. DOI:10.3390/s150203224 · 2.05 Impact Factor
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    ABSTRACT: This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.
    Sensors 02/2015; 15(2):2538-47. DOI:10.3390/s150202538 · 2.05 Impact Factor
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    ABSTRACT: The purity evaluation of deionized (DI) water is highly desirable for VLSI or ULSI industry, as the traditional "reverse osmosis filter" cannot always meet the requirement towards the DI water. The filtered DI water may still contain many contaminations which are not up to the standard for the wet cleaning of wafer surface. A novel method is presented by analyzing the residues of a water droplet after the low-temperature evaporation. The contamination contained in the water will remain during the gasification. By analyzing the residual contamination's morphology, the purity of the DI water can be estimated by employing merely a 3D laser microscope. Compared to the traditional fluorescence detecting system for water quality monitoring, it is simpler and has a lower cost. The paper describes an excellent water detection method which is meaningful for preparing ultra-pure water. Experimental results have shown that the deionized distilled (DID) water can repeatedly get a higher purity using this detection method. The DID water can be applied to the wet cleaning of wafer surface, preparation of chemical reagents and many other aspects.
    Modern Physics Letters B 01/2015; 29(03):1450271. DOI:10.1142/S0217984914502716 · 0.69 Impact Factor
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    ABSTRACT: Piezoelectric materials used in the development of nanoscale mechanical sensors, actuators and energy harvesters have received much attention. More recently, devices made of graphene are of particular interest because of graphene's intriguing electronic and mechanical properties. Intrinsic graphene has long been considered devoid of the piezoelectric effect, although flexoelectricity has been exploited to demonstrate piezoelectricity in functionalized graphene and graphene nanoribbons. The perceived lack of this property has restricted graphene's use in nanoelectromechanical systems (NEMS) for electromechanical coupling purposes. Here an unprecedented two-dimensional (2D) piezoelectric effect on a strained/unstrained graphene junction is reported. In stark contrast to the bulk piezoelectric effect that results from the occurrence of electric dipole moments in solids, the 2D piezoelectric effect arises from the charge transfer along a work function gradient introduced by the biaxial-strain-engineered band structure. The observed effect, termed the band-piezoelectric effect, exhibits an enormous magnitude due to the ultrathin structure of graphene. On the basis of the band-piezoelectric effect, a graphene nanogenerator and a pressure gauge were fabricated. The results not only provide a versatile NEMS platform for sensing, actuating and energy harvesting, but also pave the way for efficiently modulating graphene via strain engineering.
    01/2015; 7(1):e154. DOI:10.1038/am.2014.124
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    ABSTRACT: Nanogenerators (NGs) have great potential to solve the problems of energy depletion and environmental pollution. Here, two types of flexible nanogenerators (FNGs) based on graphene oxide (GO) and multiwall carbon nanotubes (MW-CNTs) are presented. The peak output voltage and current of GO based FNG reached up to 2 V and 30 nA, respectively, under 15 N force at 1 Hz. Moreover, the output voltage could be improved to 34.4 V when the frequency was increased to 10 Hz. It was also found the output voltage increased from 0.1 V to 2.0 V using a released GO structure. The other FNG was made by MW-CNTs mixed with ZnO nanoparticles (NPs). Its output voltage and power reached up to 7.5 V and 18.75 mW, respectively, which is much larger than that of bare ZnO based FNG. Furthermore, a peak voltage of 30 V could be gained by stamping one’s foot on the FNG. Finally, a modified NG was fabricated using four springs and two flexible layers. As a result, the voltage and power reached up to 9 V and 27mW, respectively. These works may bring out broad applications in energy harvesting.
    MRS Online Proceeding Library 01/2015; 1782. DOI:10.1557/opl.2015.640
  • 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.
    Tsinghua Science & Technology 01/2015; 20(3):270-276.
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    ABSTRACT: We explore a type piezoelectric material 0.9525(K0.5Na0.5NbO3)-0.0475LiTaO3 (KNN-LTS) which can be used to fabricate nanogenerator with high output voltage and current due to its high piezoelectric constant (d 33). Because of its unique structure mixed with multi-wall carbon nanotube and polydimethylsiloxane, the output voltage is up to 53 V and the output current is up to 15 uA (current density of 12.5 uA/cm2) respectively. The value of the output voltage and output current represent the highest level in the piezoelectric field reported to date. The KNN-LTS nanopowder-based nanogenerator can also be used as a sensitive motion detection sensor.
    AIP Advances 01/2015; 5(1):017102. DOI:10.1063/1.4905698 · 1.59 Impact Factor
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    ABSTRACT: We report the influences of pulse widths on the programming and erasing characteristics of diamond-like carbon films based resistive random access memory. The device can be only programmed with pulses wider than 50 ns for SET operations when the pulse voltage is 1.2V and erased with pulses narrower than 25 ns for RESET operations when the pulse voltage is 0.4 V. The formation, rupture, and re-growth of the conductive sp(2)-like graphitic filaments are proposed to be responsible for the resistive switching behaviors, based on which the pulse widths dependences on its programming and erasing properties can be further explained. (C) 2014 AIP Publishing LLC.
    Applied Physics Letters 10/2014; 105(17). DOI:10.1063/1.4898345 · 3.52 Impact Factor
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    ABSTRACT: Understanding the growth mechanism of graphene layers in chemical vapor deposition (CVD) and their corresponding Raman properties is technologically relevant and of importance for the application of graphene in electronic and optoelectronic devices. Here, we report CVD growth of single-crystal trilayer graphene (TLG) grains on Cu and show that lattice defects at the center of each grain persist throughout the growth, indicating that the adlayers share the same nucleation site with the upper layers and these central defects could also act as a carbon pathway for the growth of a new layer. Statistics shows that ABA, 30-30, 30-AB, and AB-30 make up the major stacking orientations in the CVD-grown TLG, with distinctive Raman 2D characteristics. Surprisingly, a high level of lattice defects results whenever a layer with a twist angle of θ = 30° is found in the multiple stacks of graphene layers.
    ACS Nano 10/2014; 8(10). DOI:10.1021/nn5044959 · 12.88 Impact Factor
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    ABSTRACT: Recently, two-dimensional materials such as molybdenum disulphide (MoS2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 0.5-20 cm(2)/V·s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced in the novel transistors. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm(2)/V·s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.
    Scientific Reports 08/2014; 4:5951. DOI:10.1038/srep05951 · 5.58 Impact Factor
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    ABSTRACT: A nonvolatile resistive switching random access memory (RRAM) device based on the diamond-like carbon (DLC) films and the inert metal electrodes was demonstrated. A typical unipolar resistive switching (RS) behavior without high voltage “forming process” is observed. It exhibits good scaling-down properties when negligible dependence upon the cell area is observed for VSET and IRESET decreases with the reduction of the cell area, which is suitable for practical nonvolatile memory applications. Investigations on the electron transport characteristics at HRS and LRS indicate that Frenkel–Poole emission and Ohmic Laws dominate the LRS and HRS states, respectively. Based on the conduction mechanism studies, the RS behavior is found to arise from the formation and rupture of conductive sp2-like graphitic filaments originating from the connection of conductive sp2-like carbon bonds in the predominantly sp3-like insulating carbon matrix through the electric field induced dielectric breakdown process and thermal fuse effects.
    Carbon 08/2014; 75:255–261. DOI:10.1016/j.carbon.2014.03.061 · 6.16 Impact Factor

Publication Stats

611 Citations
326.84 Total Impact Points

Institutions

  • 1998–2015
    • Tsinghua University
      • • Institute of Microelectronics
      • • Tsinghua National Laboratory for Information Science and Technology
      Peping, Beijing, China
  • 2007
    • Princeton University
      Princeton, New Jersey, United States
    • Huazhong University of Science and Technology
      • Department of Electronic Science and Technology
      Wu-han-shih, Hubei, China
  • 2002–2007
    • National Tsing Hua University
      Hsin-chu-hsien, Taiwan, Taiwan