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Timeline of Wei Pang

2018
Nov
28
Published new article




Article

On-chip acoustic mixer integration of electro-microfluidics towards in-situ and efficient mixing in droplets

Published: 28 November 2018 by Springer Nature in Microfluidics and Nanofluidics

doi: 10.1007/s10404-018-2169-7

Rapid and reliable micromixing requires continuous improvement to renovate more powerful microfluidics chip for chemosynthesis, biological assay, and drug purification. In this work, we realized rapid in-situ mixing in droplets on a closed electro-microfluidic chip. Electrowetting and 2.5 GHz acoustic wave streaming were coupled into a monolithic chip for the manipulation and active mixing of microdroplets, respectively. Finite-element analysis simulation provided three-dimensional illustrations of turbulent flow pattern, fluid velocity, and vortices core locations. We carried out mixing experiments on different scales from nanoscale molecules to microscale particles, accelerating mixing efficiency by more than 50 times compared with pure diffusion. In the enzyme catalytic reaction experiment for biological assay demonstration, mixing efficiency of biological samples improves by about one order of magnitude compared with conventional 96-well-plate assay. Limited temperature rising of mixing in microdroplets validates biological safety, which guarantees potentials of the chip in various biochemical analyses and medical applications.

0 Reads | 0 Citations
2018
Nov
22
Published new article




Article

Highly Bendable Piezoelectric Resonators for Flexible Radio-Frequency Electronics

Published: 22 November 2018 by Wiley in Advanced Electronic Materials

doi: 10.1002/aelm.201800545

As bendable, conformal electronic components, flexible gigahertz resonators are in demand as important building blocks (e.g., oscillators, filters, and signal processors) in future flexible radio‐frequency electronics for efficient wireless communication. Here, a 2.7 GHz piezoelectric thin‐film resonator (i.e., film bulk acoustic wave resonator) is presented that possesses high levels of both electrical performance and mechanical flexibility. The highly bendable resonator fabricated by FlexMEMS technology is essentially a thin‐film composite (i.e., high‐quality metal and inorganic piezoelectric layer stacks) encapsulated in polymer thin films with a total thickness of only 11.6 µm. The experimental series resonance frequency (fS), parallel resonance frequency (fP), quality factor (Q), and effective coupling coefficient ( kt eff 2) are 2.72 GHz, 2.77 GHz, 1398, and 4.39%, respectively. These parameter values are comparable to those of a conventional silicon‐based resonator. The minimum bending radius of the flexible resonator can be reduced to ≈0.5 mm with very slight electrical performance variation. Furthermore, the flexible resonator retains its mechanical and electrical stability after 2000 bending cycles. The superior mechanical flexibility and stability represent a significant advancement toward bendable, foldable, and conformal electronics working in the RF range.

0 Reads | 0 Citations
2018
Nov
01
Published new article




Article

Miniaturized polymer coated film bulk acoustic wave resonator sensor array for quantitative gas chromatographic analysis

Published: 01 November 2018 by Elsevier BV in Sensors and Actuators B: Chemical

doi: 10.1016/j.snb.2018.07.162

This paper reports a novel miniaturized detector for gas chromatography based on film bulk acoustic resonator (FBAR) sensor array. Polymer coated FBAR demonstrated detection limit of parts per million (ppm) concentrations for several volatile organic vapors. Orthogonal selectivity between n-pentane and acetone is achieved by integrating different polymer coated FBARs as sensor array. A prototype of chromatographic instrument using FBAR sensor array as detector was demonstrated by facile hyphenation of the device with commercial separation column. Such GC system is used to quantitative identification of dual gas mixture by employing Principal Component Analysis (PCA). This MEMS chemical sensor technology offers high sensing performance, miniaturized size, and low power consumption, which are critical for development of portable gas chromatography.

2 Reads | 1 Citations
2018
Jul
02
Published new article




Article

A Universal Biomolecular Concentrator To Enhance Biomolecular Surface Binding Based on Acoustic NEMS Resonator

Published: 02 July 2018 by American Chemical Society (ACS) in ACS Central Science

doi: 10.1021/acscentsci.8b00301

In designing bioassay systems for low-abundance biomolecule detection, most research focuses on improving transduction mechanisms while ignoring the intrinsically fundamental limitations in solution: mass transfer and binding affinity. We demonstrate enhanced biomolecular surface binding using an acoustic nano-electromechanical system (NEMS) resonator, as an on-chip biomolecular concentrator which breaks both mass transfer and binding affinity limitations. As a result, a concentration factor of 105 has been obtained for various biomolecules. The resultantly enhanced surface binding between probes on the absorption surface and analytes in solution enables us to lower the limit of detection for representative proteins. We also integrated the biomolecular concentrator into an optoelectronic bioassay platform to demonstrate delivery of proteins from buffer/serum to the absorption surface. Since the manufacture of the resonator is CMOS-compatible, we expect it to be readily applied to further analysis of biomolecular interactions in molecular diagnostics.

0 Reads | 0 Citations
2018
Jun
11
Published new article




Article

Acoustic Streaming and Microparticle Enrichment within a Microliter Droplet Using a Lamb-Wave Resonator Array

Published: 11 June 2018 by American Physical Society (APS) in Physical Review Applied

doi: 10.1103/physrevapplied.9.064011

We report the nonlinear acoustic streaming effect and the fast manipulation of microparticles by microelectromechanical Lamb-wave resonators in a microliter droplet. The device, consisting of four Lamb-wave resonators on a silicon die, generates cylindrical traveling waves in a liquid and efficiently drives nine horizontal vortices within a 1−μl droplet; the performance of the device coincides with the numerical model prediction. Experimentally, the particles are enriched at the stagnation center of the main vortex on the free surface of the droplet in open space without microfluidic channels. In addition, the trajectories of the particles in the droplet can be controlled by the excitation power.

3 Reads | 0 Citations
2018
Jun
06
Published new article




Article

Hypersonic-Induced 3D Hydrodynamic Tweezers for Versatile Manipulations of Micro/Nanoscale Objects

Published: 06 June 2018 by Wiley in Particle & Particle Systems Characterization

doi: 10.1002/ppsc.201800068

Developing microrobots for precisely manipulating micro/nanoscale objects has triggered tremendous research interest for various applications in biology, chemistry, physics, and engineering. Here, a novel hypersonic‐induced hydrodynamic tweezers (HSHTs), which use gigahertz nano‐electromechanical resonator to create localized 3D vortex streaming array for the capture and manipulation of micro‐ and nanoparticles in three orientations: transportation in a plane and self‐rotation in place, are presented. 3D vortex streaming can effectively pick up particles from the flow, whereas the high‐speed rotating vortices are used to drive self‐rotation simultaneously. By tuning flow rate, the captured particles can be delivered, queued, and selectively sorted through the 3D HSHTs. Through numerical simulations and theoretical analysis, the generation of the 3D vortex and the mechanism of the particles manipulation by ultrahigh frequency acoustic wave are demonstrated. Benefitting from the advantages of the acoustic and hydrodynamic method, the developed HSHTs work in a precise, noninvasive, label‐free, and contact‐free manner, enabling wide applications in micro/nanoscale manipulations and biomedical research.

6 Reads | 0 Citations
2018
Apr
20
Published new article






Piezoelectric Micro/Nano Mechanical Devices for Frequency Control and Chemical Sensing

Published: 20 April 2018 by Springer Nature in Micro/Nano Technologies

doi: 10.1007/978-981-10-5945-2_23

This chapter reports on the state of the art of piezoelectric micro-/nano-mechanical devices in frequency control and sensing applications. Recent studies on bulk acoustic wave (BAW) devices are introduced, including investigation of high-coupling materials and filter and oscillator designs. A novel class of frequency devices based on Lamb waves is also reviewed. Micro- and nano-mechanical sensors for various sensing applications and integrated module are outlined.

0 Reads | 0 Citations
2018
Mar
30
Published new article




Article

Flexible Film Bulk Acoustic Wave Filters toward Radiofrequency Wireless Communication

Published: 30 March 2018 by Wiley in Small

doi: 10.1002/smll.201703644

This paper presents a flexible radiofrequency filter with a central frequency of 2.4 GHz based on film bulk acoustic wave resonators (FBARs). The flexible filter consists of five air‐gap type FBARs, each comprised of an aluminum nitride piezoelectric thin film sandwiched between two thin‐film electrodes. By transfer printing the inorganic film structure from a silicon wafer to an ultrathin polyimide substrate, high electrical performance and mechanical flexibility are achieved. The filter has a peak insertion loss of −1.14 dB, a 3 dB bandwidth of 107 MHz, and a temperature coefficient of frequency of −27 ppm °C−1. The passband and roll‐off characteristics of the flexible filter are comparable with silicon‐based commercial products. No electrical performance degradation and mechanical failure occur under bending tests with a bending radius of 2.5 mm or after 100 bending cycles. The flexible FBAR filters are believed to be promising candidates for future flexible wireless communication systems.

5 Reads | 0 Citations
2018
Jan
25
Published new article




Article

Dual-Mode Gas Sensor Composed of a Silicon Nanoribbon Field Effect Transistor and a Bulk Acoustic Wave Resonator: A Case...

Published: 25 January 2018 by MDPI in Sensors

doi: 10.3390/s18020343

In this paper, we develop a novel dual-mode gas sensor system which comprises a silicon nanoribbon field effect transistor (Si-NR FET) and a film bulk acoustic resonator (FBAR). We investigate their sensing characteristics using polar and nonpolar organic compounds, and demonstrate that polarity has a significant effect on the response of the Si-NR FET sensor, and only a minor effect on the FBAR sensor. In this dual-mode system, qualitative discrimination can be achieved by analyzing polarity with the Si-NR FET and quantitative concentration information can be obtained using a polymer-coated FBAR with a detection limit at the ppm level. The complementary performance of the sensing elements provides higher analytical efficiency. Additionally, a dual mixture of two types of freons (CFC-113 and HCFC-141b) is further analyzed with the dual-mode gas sensor. Owing to the small size and complementary metal-oxide semiconductor (CMOS)-compatibility of the system, the dual-mode gas sensor shows potential as a portable integrated sensing system for the analysis of gas mixtures in the future.

8 Reads | 1 Citations
2017
Nov
13
Published new article




Article

Oxygen Plasma-Treated Graphene Oxide Surface Functionalization for Sensitivity Enhancement of Thin-Film Piezoelectric Ac...

Published: 13 November 2017 by American Chemical Society (ACS) in ACS Applied Materials & Interfaces

doi: 10.1021/acsami.7b09547

In this work, we presented a thin-film piezoelectric acoustic gas sensor with enhanced sensitivity by a surface modification strategy of oxygen plasma treated graphene oxide (GO) functionalization. By exposing to ammonia vapor (NH3) of various concentrations at controlled temperature and humidity, the characteristics of the GO-coated acoustic sensor were investigated, i.e. sensitivity, linearity, response, and recovery time. Oxygen plasma treatment of the GO-coated sensor further enhanced the sensitivity compared with the freshly prepared GO-coated sensor. The mechanism of oxygen plasma treatment effect on the GO-coated sensor was discussed based on characterizations of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscope (SEM), and precise weighing of the acoustic sensor. It was found that the oxygen plasma treatment introduces numerous defects to GO flakes, which are uniformly distributed across the GO surface, providing more gas molecule binding sites.

0 Reads | 5 Citations
2017
Nov
13
Published new article




Article

On-chip nanofluidic integration of acoustic sensors towards high Q in liquid

Published: 13 November 2017 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4992046

0 Reads | 0 Citations
2017
Oct
01
Published new article




Article

Biomolecular stiffness detection based on positive frequency shift of CMOS compatible gigahertz solidly mounted resonato...

Published: 01 October 2017 by Elsevier BV in Biosensors and Bioelectronics

doi: 10.1016/j.bios.2017.05.002

In this work, gigahertz solidly mounted resonators (SMRs) (2.5GHz) were designed and fabricated to construct a novel particle-resonator system to achieve the biomolecular stiffness sensing in real time. The positive frequency shift of the system was used to estimate the stiffness of biomolecules connecting between the SMR and attached particles. The working principle was revealed by the mathematical analysis of the general block-spring model of the system. Further interpretations about the mechanism of such elastic interaction from the perspective of acoustic resonant modes of SMRs were given by finite element method. Biotin-streptavidin, antibody and antigen binding system were used as model molecular linkers to study the frequency shift varied with different particle diameters and particle densities. Different linker stiffness was realized by adjusting the concentrations of antigens connected with particles which form specific binding with antibodies immobilized on the SMR. The results fairly agree with the simulation results demonstrating the proposed particle-resonator system as an effective method to realize the real-time biomolecular stiffness detection.

2 Reads | 0 Citations
2017
Aug
28
Published new article






Piezoelectric Micro/Nano Mechanical Devices for Frequency Control and Chemical Sensing

Published: 28 August 2017 by Springer Nature in Micro/Nano Technologies

doi: 10.1007/978-981-10-2798-7_23-1

This chapter reports on the state of the art of piezoelectric micro-/nano-mechanical devices in frequency control and sensing applications. Recent studies on bulk acoustic wave (BAW) devices are introduced, including investigation of high-coupling materials and filter and oscillator designs. A novel class of frequency devices based on Lamb waves is also reviewed. Micro- and nano-mechanical sensors for various sensing applications and integrated module are outlined.

0 Reads | 0 Citations
2017
Aug
07
Published new article




Article

Mechanical Vibration Measurement of Solidly Mounted Resonator in Fluid by Atomic Force Microscopy

Published: 07 August 2017 by MDPI in Micromachines

doi: 10.3390/mi8080244

The very small vibration of a solidly-mounted resonator (SMR) in fluid may trigger a relatively large motion of the covering fluid, which was implied by our protein-related experimental results. Therefore, a series of experimental methods for characterizing the mechanical longitudinal vibration of the SMR and the corresponding out-of-plane dynamic response of the fluid above the SMR surface is described in this paper. A SMR device with theoretical resonance frequency of 2.5 GHz was driven by an amplitude-modulated (AM) signal, in which the amplitude is modulated by a signal of the second resonance frequency of the atomic force microscope (AFM) cantilever. A lock-in amplifier is used to demodulate the vibration response of the AFM cantilever, which is proportional to the amplitude of the sample vibration in contact mode and tapping mode. The amplitude-frequency curve of the SMR surface is obtained in contact mode with a relatively stronger interaction force between the AFM tip and the SMR surface. The amplitude-frequency curve of the motion of the liquid above the SMR device and the peak amplitude of the fluid at different distances above the SMR surface are measured in tapping mode with a relatively weak interaction force between the AFM tip and the fluid sample.

2 Reads | 0 Citations
2017
Jul
10
Published new article




Article

A flexible, gigahertz, and free-standing thin film piezoelectric MEMS resonator with high figure of merit

Published: 10 July 2017 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4993901

4 Reads | 2 Citations
2017
Jun
26
Published new article




Article

Resonant and resistive dual-mode uncooled infrared detectors toward expanded dynamic range and high linearity

Published: 26 June 2017 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4990285

0 Reads | 1 Citations
2017
Jun
26
Published new article




Article

Novel Gas Sensor Arrays Based on High-Q SAM-Modified Piezotransduced Single-Crystal Silicon Bulk Acoustic Resonators

Published: 26 June 2017 by MDPI in Sensors

doi: 10.3390/s17071507

This paper demonstrates a novel micro-size (120 μm × 200 μm) piezoelectric gas sensor based on a piezotransduced single-crystal silicon bulk acoustic resonator (PSBAR). The PSBARs operate at 102 MHz and possess high Q values (about 2000), ensuring the stability of the measurement. A corresponding gas sensor array is fabricated by integrating three different self-assembled monolayers (SAMs) modified PSBARs. The limit of detection (LOD) for ethanol vapor is demonstrated to be as low as 25 ppm with a sensitivity of about 1.5 Hz/ppm. Two sets of identification code bars based on the sensitivities and the adsorption energy constants are utilized to successfully discriminate isopropanol (IPA), ethanol, hexane and heptane vapors at low and high gas partial pressures, respectively. The proposed sensor array shows the potential to form a portable electronic nose system for volatile organic compound (VOC) differentiation.

4 Reads | 0 Citations
2017
Jun
12
Published new article




Article

Modulation of acousto-electric current using a hybrid on-chip AlN SAW/GFET device

Published: 12 June 2017 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4986481

0 Reads | 2 Citations
2017
Jun
05
Published new article




Article

Correction: Liu, W. et al. A Highly Sensitive Humidity Sensor Based on Ultrahigh-Frequency Microelectromechanical Resona...

Published: 05 June 2017 by MDPI in Micromachines

doi: 10.3390/mi8060178

Note: In lieu of an abstract, this is an excerpt from the first page.Excerpt In the published paper [1], there is an error in Figure 3.

2 Reads | 0 Citations
2017
May
12
Published new article




Article

Enhanced Sensitivity of MoTe2 Chemical Sensor through Light Illumination

Published: 12 May 2017 by MDPI in Micromachines

doi: 10.3390/mi8050155

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) semiconducting materials have recently attracted wide attention and been regarded as promising building blocks for chemical sensors due to their high surface-to-volume ratio. However, their low response hinders the realization of high-performance 2D TMDCs chemical sensors. Here, we demonstrate the improvement of sensing performance of molybdenum ditelluride (MoTe2) gas sensor through continuous light illumination. The dependence of sensing performance on the energy of photons and light intensity is systematically studied. The response to NH3 is dramatically enhanced by more than 25 times under 254 nm ultraviolet (UV) light illumination with intensity of 2.5 mW/cm2. Moreover, a remarkable low detection limit of 3 ppb is achieved, which is improved by 80 times compared with that in dark condition. The results demonstrate that light illumination is a promising method to improve the sensitivity of 2D TMDCs chemical sensors.

0 Reads | 3 Citations
2017
Apr
05
Published new article




Article

A Highly Sensitive Humidity Sensor Based on Ultrahigh-Frequency Microelectromechanical Resonator Coated with Nano-Assemb...

Published: 05 April 2017 by MDPI in Micromachines

doi: 10.3390/mi8040116

We developed a highly sensitive humidity sensor based on the combination of ultrahigh-frequency film bulk acoustic resonator (FBAR) and nano-assembled polyelectrolyte (PET) thin films. The water molecule absorption efficiency was optimized by forming loosely-packed PET nanostructures. Then, the humidity sensing characteristics were analyzed in terms of sensitivity, linearity, reversibility, stability and detection limit. As a result, PET-coated FBAR exhibits excellent humidity sensitivity of 2202.20 Hz/ppm, which is five orders of magnitude higher than quartz crystal microbalance (QCM). Additionally, temperature dependence was investigated with the result that PET-coated FBAR possessed a higher sensitivity at low temperature. Furthermore, we realized the selective detection of water vapor from volatile organic compounds (VOCs) with respect to the polarity property. Owing to the high sensitivity, miniaturized size and ultrahigh operating frequency, PET-coated FBAR is uniquely favorable as a wireless humidity sensor node to integrate into wireless sensor networks (WSNs).

3 Reads | 4 Citations
2017
Feb
13
Published new article




Article

Hypersonic Poration: A New Versatile Cell Poration Method to Enhance Cellular Uptake Using a Piezoelectric Nano-Electrom...

Published: 13 February 2017 by Wiley in Small

doi: 10.1002/smll.201602962

Efficient delivery of genes and therapeutic agents to the interior of the cell is critical for modern biotechnology. Herein, a new type of chemical-free cell poration method—hypersonic poration—is developed to improve the cellular uptake, especially the nucleus uptake. The hypersound (≈GHz) is generated by a designed piezoelectric nano-electromechanical resonator, which directly induces normal/shear stress and “molecular bombardment” effects on the bilayer membranes, and creates reversible temporal nanopores improving the membrane permeability. Both theory analysis and cellular uptake experiments of exogenous compounds prove the high delivery efficiency of hypersonic poration. Since target molecules in cells are accumulated with the treatment, the delivered amount can be controlled by tuning the treatment time. Furthermore, owing to the intrinsic miniature of the resonator, localized drug delivery at a confined spatial location and tunable arrays of the resonators that are compatible with multiwell plate can be achieved. The hypersonic poration method shows great delivery efficacy combined with advantage of scalability, tunable throughput, and simplification in operation and provides a potentially powerful strategy in the field of molecule delivery, cell transfection, and gene therapy.

5 Reads | 7 Citations
2016
Dec
26
Published new article




Article

Wireless gas sensing based on a passive piezoelectric resonant sensor array through near-field induction

Published: 26 December 2016 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4973280

5 Reads | 1 Citations
2016
Nov
01
Published new article




Article

Acoustically Triggered Disassembly of Multilayered Polyelectrolyte Thin Films through Gigahertz Resonators for Controlle...

Published: 01 November 2016 by MDPI in Micromachines

doi: 10.3390/mi7110194

Controlled drug release has a high priority for the development of modern medicine and biochemistry. To develop a versatile method for controlled release, a miniaturized acoustic gigahertz (GHz) resonator is designed and fabricated which can transfer electric supply to mechanical vibrations. By contacting with liquid, the GHz resonator directly excites streaming flows and induces physical shear stress to tear the multilayered polyelectrolyte (PET) thin films. Due to the ultra-high working frequency, the shear stress is greatly intensified, which results in a controlled disassembling of the PET thin films. This technique is demonstrated as an effective method to trigger and control the drug release. Both theory analysis and controlled release experiments prove the thin film destruction and the drug release.

0 Reads | 1 Citations
2016
Aug
05
Published new article




Article

A Modified Lattice Configuration Design for Compact Wideband Bulk Acoustic Wave Filter Applications

Published: 05 August 2016 by MDPI in Micromachines

doi: 10.3390/mi7080133

High-performance bulk acoustic wave (BAW) filters have been widely applied in the advanced radio frequency (RF) wireless communication systems in the past decade. However, the demand for filters with large bandwidth, up to 10%, still puts a significant stress on the typical aluminum nitride (AlN)-based BAW filters. In this work, a modified lattice configuration is proposed to achieve a wideband filter response using AlN-based BAW resonators. The single stage of this novel topology comprises two auxiliary inductors paralleled in the balanced input and output of the conventional lattice topology. In multi-stage configuration, adjacent two auxiliary inductors can be combined into one; thus, the number of auxiliary inductors decreases exponentially, enabling the compact integration of filter chips. The circuit analysis is performed to reveal the working principle of this configuration. The systematic design methodology is developed ranging from the schematic design to the electromagnetic (EM) simulation. For proof-of-concept validation purposes, a prototype film bulk acoustic wave filter in this configuration is designed and fabricated. The measured 3-dB bandwidth is 400 MHz at the central frequency of 3.25 GHz (12.3% relative bandwidth), which demonstrates a huge superiority in contrast with the conventional ladder and lattice topologies.

0 Reads | 2 Citations
2016
Feb
25
Published new article




Article

A Microfluidic-Based Fabry Pérot Gas Sensor

Published: 25 February 2016 by MDPI in Micromachines

doi: 10.3390/mi7030036

We developed a micro-gas detector based on a Fabry-Pérot (FP) cavity embedded in a microfluidic channel. The detector was fabricated in two steps: a silicon substrate was bonded to a glass slide curved with a micro-groove, forming a microfluidic FP cavity; then an optical fiber was inserted through a hole drilled at the center of the groove into the microfluidic FP cavity, forming an FP cavity. The light is partially reflected at the optical fiber endface and the silicon surface, respectively, generating an interference spectrum. The detection is implemented by monitoring the interference spectrum shift caused by the refractive index change of the FP cavity when a gas analyte passes through. This detection mechanism (1) enables detecting a wide range of analytes, including both organic and inorganic (inertia) gases, significantly enhancing its versatility; (2) does not disturb any gas flow so that it can collaborate with other detectors to improve sensing performances; and (3) ensures a fast sensing response for potential applications in gas chromatography systems. In the experiments, we used various gases to demonstrate the sensing capability of the detector and observed drastically different sensor responses. The estimated sensitivity of the detector is 812.5 nm/refractive index unit (RIU) with a detection limit of 1.2 × 10−6 RIU assuming a 1 pm minimum resolvable wavelength shift.

4 Reads | 1 Citations
2016
Feb
01
Published new article




Article

Microchip based electrochemical-piezoelectric integrated multi-mode sensing system for continuous glucose monitoring

Published: 01 February 2016 by Elsevier BV in Sensors and Actuators B: Chemical

doi: 10.1016/j.snb.2015.09.022

We presented a MEMS multi-mode sensing system by integrating electrochemical working electrode and solid-mounted thin-film piezoelectric resonator (SMR) on a single micro-sized chip, which is capable of detecting three sensing modes of electrochemistry, gravimetry and viscometry. As a model test sample, glucose concentration was successfully monitored using this integrated sensor. The electrochemical sensor amperometrically detected glucose concentration change, and SMR tracked the concentration variation through impedance response to viscosity. Optimized number of single-walled carbon nanotubes (SWCNTs) – poly (dimethyldiallylammonium chloride) (PDDA) / glucose oxidase (GOD) modification layers was also determined with the help of SMR by monitoring the mass-sensitive frequency shift. SMR proved to be a suitable support for chip-integrated electrochemical sensor for glucose detection. This integrated chip sensor can be conveniently fabricated with high throughput, shows significant potential for chemical and biological sensing applications. Graphical

4 Reads | 8 Citations
2016
Jan
18
Published new article




Article

Acoustically induced current in graphene by aluminum nitride transducers

Published: 18 January 2016 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4940400

We report on the excitation of acousto-eletric (AE) charge transport in monolayergraphene by acoustic transducers based on aluminum nitride thin films. The acoustic waves induced macroscopic current flow that linearly scaled with input power. The AE current exhibited unique frequency dependence due to special configuration and piezoelectric properties of the transducer, which led to transitions between traveling and standing acoustic waves across a characteristic frequency. A Finite Element model was built to investigate and understand the phenomena and the underlying mechanisms.

0 Reads | 4 Citations
2015
Dec
14
Published new article




Article

Spurious-free Lamb wave resonators with protrusion structures

Published: 14 December 2015 by AIP Publishing in Applied Physics Letters

doi: 10.1063/1.4937736

In this letter, we demonstrate a technique to eliminate the spurious modes in aluminum nitrideLamb waveresonators (LWRs). The transverse acoustic wave characteristics are examined, and a resonance modulation theory on the regulation of mechanical boundary conditions is deducted. As examples of embodiments, vertical and lateral protrusion structures are proposed for the suppression. Finite element analysis verifies that the employment of these structures effectively restrains the transverse modes, and the measured electrical performance of the LWR with protrusions demonstrates an 11 dB reduction in the spurious response. In this letter, we demonstrate a technique to eliminate the spurious modes in aluminum nitrideLamb waveresonators (LWRs). The transverse acoustic wave characteristics are examined, and a resonance modulation theory on the regulation of mechanical boundary conditions is deducted. As examples of embodiments, vertical and lateral protrusion structures are proposed for the suppression. Finite element analysis verifies that the employment of these structures effectively restrains the transverse modes, and the measured electrical performance of the LWR with protrusions demonstrates an 11 dB reduction in the spurious response.

0 Reads | 3 Citations
2015
Sep
08
Published new article




Article

A Novel Bulk Acoustic Wave Resonator for Filters and Sensors Applications

Published: 08 September 2015 by MDPI in Micromachines

doi: 10.3390/mi6091306

Bulk acoustic wave (BAW) resonators are widely applied in filters and gravimetric sensors for physical or biochemical sensing. In this work, a new architecture of BAW resonator is demonstrated, which introduces a pair of reflection layers onto the top of a thin film bulk acoustic resonator (FBAR) device. The new device can be transformed between type I and type II dispersions by varying the thicknesses of the reflection layers. A computational modeling is developed to fully investigate the acoustic waves and the dispersion types of the device theoretically. The novel structure makes it feasible to fabricate both type resonators in one filter, which offers an effective alternative to improve the pass band flatness in the filter. Additionally, this new device exhibits a high quality factor (Q) in the liquid, which opens a possibility for real time measurement in solutions with a superior limitation of detection (LOD) in sensor applications.

0 Reads | 1 Citations
2015
Aug
06
Published new article




Article

Detection of Volatile Organic Compounds Using Microfabricated Resonator Array Functionalized with Supramolecular Monolay...

Published: 06 August 2015 by American Chemical Society (ACS) in ACS Applied Materials & Interfaces

doi: 10.1021/acsami.5b04385

This paper describes the detection of volatile organic compounds (VOCs) using an e-nose type integrated microfabricated sensor array, in which each resonator is coated with different supramolecular monolayers: p-tert-butyl calix[8]arene (Calix[8]arene), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (Porphyrin), β-cyclodextrin (β-CD), and cucurbit[8]uril (CB[8]). Supramolecular monolayers fabricated by Langmuir–Blodgett techniques work as specific sensing interface for different VOCs recognition which increase the sensor selectivity. Microfabricated ultrahigh working frequency film bulk acoustic resonator (FBAR) transducers (4.4 GHz) enable their high sensitivity toward monolayer gas sensing which facilitate the analyses of VOCs adsorption isotherms and kinetics. Two affinity constants (K1, K2) are obtained for each VOC, which indicate the gas molecule adsorption happen inside and outside of the supramolecular cavities. Additional kinetic information on adsorption and desorption rate constants (ka, kd) are obtained as well from exponential fitting results. The five parameters, one from the conventional frequency shift signals of mass transducers and the other four from the indirect analyses of monolayer adsorption behaviors, thus enrich the sensing matrix (Δf, K1, K2, ka, kd) which can be used as multiparameter fingerprint patterns for highly selective detection and discrimination of VOCs.

5 Reads | 19 Citations
2015
Jun
19
Published new article




Article

Dynamics of Electrowetting Droplet Motion in Digital Microfluidics Systems: From Dynamic Saturation to Device Physics

Published: 19 June 2015 by MDPI in Micromachines

doi: 10.3390/mi6060778

A quantitative description of the dynamics of droplet motion has been a long-standing concern in electrowetting research. Although many static and dynamic models focusing on droplet motion induced by electrowetting-on-dielectric (EWOD) already exist, some dynamic features do not fit these models well, especially the dynamic saturation phenomenon. In this paper, a dynamic saturation model of droplet motion on the single-plate EWOD device is presented. The phenomenon that droplet velocity is limited by a dynamic saturation effect is precisely predicted. Based on this model, the relationship between droplet motion and device physics is extensively discussed. The static saturation phenomenon is treated with a double-layer capacitance electric model, and it is demonstrated as one critical factor determining the dynamics of droplet motion. This work presents the relationship between dynamics of electrowetting induced droplet motion and device physics including device structure, surface material and interface electronics, which helps to better understand electrowetting induced droplet motions and physics of digital microfluidics systems.

5 Reads | 4 Citations
2015
Feb
12
Published new article




Article

Design and fabrication of aluminum nitride Lamb wave resonators towards high figure of merit for intermediate frequency ...

Published: 12 February 2015 by IOP Publishing in Journal of Micromechanics and Microengineering

doi: 10.1088/0960-1317/25/3/035016

A design guideline for one-port aluminum nitride (AlN) Lamb wave resonators (LWRs) working at S0 mode with high performance is reported. A fabricated 252 MHz LWR, with an aperture of 200 μm, 12 fingers, and 1.5 μm thick AlN, is found to have a remarkably high figure of merit (FOM), which exhibits a high ratio of the resistance at parallel resonance (Rp) to the resistance at series resonance (Rs) of 1317 and a corresponding product of the effective coupling coefficient (k2eff) and quality factor (Q) exceeding 52. Consisting of such resonators, a 6-stage ladder filter with a low pass-band insertion loss (IL) of 4.5 dB and steep filter skirts is achieved, offering significant advantage of size savings.

2 Reads | 5 Citations
2013
Nov
11
Published new article




Article

Power enhancement and phase regimes in embedded microring resonators in analogy with electromagnetically induced transpa...

Published: 11 November 2013 by The Optical Society in Optics Express

doi: 10.1364/oe.21.028414

This erratum amends some typographical errors, and incorrect data in a figure in our previous paper [Opt. Express 21, 20179-20186 (2013)]. It should be mentioned that the corrections do not affect the device performance or the conclusions.

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2013
Oct
30
Published new article




Article

Phase characteristics of an electromagnetically induced transparency analogue in coupled resonant systems

Published: 30 October 2013 by IOP Publishing in New Journal of Physics

doi: 10.1088/1367-2630/15/10/103033

Electromagnetically induced transparency (EIT) and EIT-like effects have been investigated in a wide variety of coupled resonant systems. Here, a classification of the phase characteristics of the EIT-like spectral responses is presented. Newly identified phase responses reveal unexplored operation regimes of EIT-like systems. Taking advantage of these new phase regimes, one can obtain group delay, dispersion and nonlinearity properties greatly enhanced by almost one order of magnitude, compared to the traditionally constructed EIT-like devices, all of which breaks the fundamental limitation (e.g. delay–bandwidth product) intrinsic to atomic EIT and EIT-like effects. Optical devices and electrical circuits are analyzed as examples showing the universality of our finding. We show that cavity quantum electrodynamics (QED)-based quantum phase gates can be greatly improved to achieve a phase shift of π. The new phase characteristics are also believed to be useful to build novel doubly resonant devices in quantum information based cavity QED, optomechanics and metamaterials.

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