Justin Kuo’s research while affiliated with Cornell University and other places

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Publications (11)


Towards GHz Ultrasound Enabled Noninvasive Hydrogel Metrology for Mechanobiology
  • Conference Paper

January 2024

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17 Reads

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Frederick Sebastian

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Figure 1 A) Four pixels (50 µm * 50 µm each) with integrated CMOS T/R circuits. B) Schematic showing ultrasonic imaging of nematodes.
Figure 2. Series of ultrasonic images (reflected echo) shows nematode (S. feltiae) moving on the imager surface. The white scale bar corresponds to 300 µm.
Real-time GHz Ultrasonic Imaging of Nematodes at Microscopic Resolution
  • Article
  • Full-text available

August 2022

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81 Reads

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3 Citations

Microscopy and Microanalysis

This work reports high-frequency ultrasonic imaging to visualize and study microscopic pests such as nematodes. This imaging modality using ultrasound instead of light enables visualizing nematodes even under the soil. This GHz technology uses a compact 128 x 128-pixel array of transducers that allow imaging at a sampling rate of up to 12 fps. The images can be viewed in real-time and further processed to measure the worms’ spatial dimensions such as length, width, as well as velocity. Here, we show that the ultrasonic imaging approach can be a powerful tool to visualize and detect microscopic pests such as nematodes and study their behavior in their natural habitat.

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Anisotropic Acoustodynamics in Gigahertz Piezoelectric Ultrasonic Transducers

July 2022

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39 Reads

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3 Citations

IEEE Electron Device Letters

In this work, we employed our newly developed optical imaging method to probe detailed acoustodynamic physics in gigahertz unreleased ultrasonic transducers based on an AlN-on-silicon system, revealing mode superposition, anisotropic transduction, and dynamic mode evolution. Superpositioned upon the dominant breathing mode along the vertical direction of the AlN layer, multiple resonant lateral modes are identified, and they are shown to evolve into a surface mode beyond the piezoelectric transduction envelope, with strong anisotropic transduction brought by the shear motion of silicon. This acoustodynamic property is important for verifying and further improving design theories of broadband piezoelectric transducers and thin film piezoelectric-on-substrate systems in general.


Instrument for stroboscopic optical sampling
a Schematic layout of the optical set-up. NPBS non-polarizing beam splitter, PBS polarizing beam splitter, PD photodetector, Ref. M reference mirror, λ/4 FR quarter-wave Fresnel rhomb (45° polarized), Piezo piezoelectric nanopositioner. The laser is collimated and 45° polarized before entering the NPBS. λ/4 FRs are used to manipulate laser polarization due to their wide spectral flatness. b Electrical spectrum of the laser pulse train obtained by directly measuring a split of the ultrafast laser using a fast PD (12.5 GHz bandwidth) and a wide-band spectrum analyzer, showing an RF frequency comb with teeth equally spaced by the laser repetition rate, fp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f}_{p}$$\end{document}. c Schematic layout of the electronics for device excitation, lock-in reference generation, and signal detection. d Schematic explanation of stroboscopic optical sampling in the frequency domain where beating the excitation signal, fex\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f}_{{ex}}$$\end{document}, with the RF comb using the tooth at nfp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n{f}_{p}$$\end{document}, results in a low-frequency beat note at fb\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f}_{b}$$\end{document}.
Measuring nanomechanical vibrations up to 12 GHz
a Optical micrograph of the bulk acoustic wave resonator (BAW) with the focused laser spot near its center. b Broadband frequency response with an applied RF power of 10 mW as shown in green. The drive frequency varies from 1.002 to 12.002 GHz with a step size of 0.050 GHz. The error bars represent ±1σ. The detection bandwidth is 1 Hz for all measurements. c The fifth resonance at 10.752 GHz grows in amplitude with varying applied RF power of 1, 2, 3.2, 5, 8, 10, 12.6, 20, and 31.6 mW, respectively. d, e Mapping the absolute vibration amplitude and phase at 2.352 and 6.552 GHz, respectively. The scan area is 73 µm by 73 µm, the scan step size is 0.73 µm, and the laser spot diameter is ~1.9 µm.
Imaging high-Q micromechanical vibrations
a Optical micrograph of the BAR with a schematic drawing of the applied DC and RF power. b Frequency response of the third width mode where the displacement amplitude and phase are shown in black and blue, respectively, for a DC bias of 20 V and an RF power of 10 mW. The displacement amplitude shown with hollow circles is for a DC bias of 20 V and the RF drive signal disconnected. c, d Mapping the BAR vertical vibration amplitude and phase at 0.9827 GHz. The black lines represent the outer dimensions of the BAR, 11.5 μm × 65 μm. Combining amplitude and phase results in a 3D mapping of the mechanical resonance, as shown in (e). It matches with the resonance mode shape calculated by finite-element analysis for the third width-extensional mode shown in (f).
Noise of stroboscopic optical sampling at super high frequencies
a Comparison between the noise floor of this work, obtained by disconnecting the power supply to the device under test (shown in red), and the noise floor for state-of-the-art CW laser interferometry12,16,20 (shown in blue), for both measurement bandwidth and noise floor. b The root mean square (RMS) vibration amplitude of the third mode (6.552 GHz) and fifth mode (10.752 GHz) of the BAW while the excitation power is gradually reduced, yielding a noise floor around 55 fm for a 1 s averaging time (red dash-dot line). In both panels (a) and (b), error bars represent ±1σ. The relationship between the displacement and the square root of the RF power is linear as expected because the driven motion is governed by the inverse piezoelectric coupling, ε3=d33E3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\varepsilon }_{3}={d}_{33}{E}_{3}$$\end{document}. The arrow indicates that changes in vibration amplitude below 10 fm can be observed when the excitation power is varied.
Vibrational wave field mapping and acoustic dispersion
a Mapping of vibration amplitude and phase of the BAW for a wide range of super high frequencies. b Spatial 2-dimensional fast Fourier transforms (2D-FFT) of the phase mappings for four representative frequencies. c Dispersion diagram extracted from the 2D-FFTs of the phase mappings from 1 to 4 GHz, showing four acoustic modes in the BAW. See Supplementary Note 5 for more data. TE1 thickness-extensional mode, TS1 thickness-shear mode. κ is defined as 1/λa here, where λa is the acoustic wavelength.
Femtometer-amplitude imaging of coherent super high frequency vibrations in micromechanical resonators

February 2022

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266 Reads

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23 Citations

Dynamic measurement of femtometer-displacement vibrations in mechanical resonators at microwave frequencies is critical for a number of emerging high-impact technologies including 5G wireless communications and quantum state generation, storage, and transfer. However, the resolution of continuous-wave laser interferometry, the method most commonly used for imaging vibration wavefields, has been limited to vibration amplitudes just below a picometer at several gigahertz. This is insufficient for these technologies since vibration amplitudes precipitously decrease for increasing frequency. Here we present a stroboscopic optical sampling approach for the transduction of coherent super high frequency vibrations. Phase-sensitive absolute displacement detection with a noise floor of 55 fm/√Hz for frequencies up to 12 GHz is demonstrated, achieving higher bandwidth and significantly lower noise floor simultaneously compared to previous work. An acoustic microresonator with resonances above 10 GHz and displacements smaller than 70 fm is measured using the presented method to reveal complex mode superposition, dispersion, and anisotropic propagation.








Citations (7)


... However, the spatial resolution (0.5 -2mm) provided by this frequency range is insufficient for smaller organisms to capture their fine structural details. On the other hand, GHz frequencies offer significantly higher resolution of ∼0.5 m to 50 , which have been previously used to study cells [9], [10], soil nematodes [11], thin chitosan films [12], and metamaterial lenses [13]. Therefore, GHz Ultrasonic Imaging has the potential to resolve mechanical properties of C. elegans at a higher resolution. ...

Reference:

Modeling and Imaging of GHz Ultrasonic Impedance of C. elegans
Real-time GHz Ultrasonic Imaging of Nematodes at Microscopic Resolution

Microscopy and Microanalysis

... Most high piezoelectric response and large ferroelectric polarization in experiments occurred in tetragonal phase or mixed phases 13 . Here, we focus on the P4mm (space group) tetragonal phase (other tetragonal perovskite phases are not ferroelectric or piezoelectric) and a longstanding problem, piezoelectric anisotropy, which is fundamentally important for modern engineering applications like ultrasonic transducers 14 and robotic metamaterials 15 . Highly anisotropic materials can provide minimal noise from lateral vibrations, greatly reducing manufacturing costs by skipping the precise control of the size of pezoelectric vibrator, eg., the length/thickness ratio, to produce the clean thickness resonance mode. ...

Anisotropic Acoustodynamics in Gigahertz Piezoelectric Ultrasonic Transducers
  • Citing Article
  • July 2022

IEEE Electron Device Letters

... 28 Here, we demonstrate a method for optically measuring and manipulating the mechanical resonator of a YIG microsphere using optical heterodyne detection. [29][30][31][32][33] This technique allows for highly accurate retrieval of vibration information from the YIG sphere, including center frequency, amplitude, and linewidth. Our optical measurements have good agreement with microwave measurements, while also providing spatial resolution by mapping the distribution of mechanical vibrations along the equator of the YIG sphere. ...

Femtometer-amplitude imaging of coherent super high frequency vibrations in micromechanical resonators

... 10 The phase-shift method was used by Abdelmejeed et al. to measure the temperature of a silicon wafer using a voltage control oscillator. 11 The thickness of the sample investigated (0.65 mm) is small when compared to many machining applications. The attenuation of the signal in a larger workpiece means that this signal source would not be appropriate. ...

A CMOS compatible GHz ultrasonic pulse phase shift based temperature sensor
  • Citing Conference Paper
  • January 2018

... CMOS-integrated GHz transducers can create compact devices, enabling low cost and miniature implementation. [64][65][66][67][68] Furthermore, this technique is label-free, and does not require surface functionalization to capture the analyte of interest as it simply relies on the acoustic impedance measurement. Representative of this technology, this paper reports measurements with GHz ultrasonic bulk waves generated by a 70 mm square aluminum nitride, or AlN thin-film transducers fabricated on a silicon wafer. ...

64-Pixel solid state CMOS compatible ultrasonic fingerprint reader
  • Citing Conference Paper
  • January 2017

... The center frequency for GHz transducers is set by the AlN and top dielectric thin film layer thicknesses, but several key functions are lithographically definable such as adjusting acoustic beam width through transducer sizing, adjusting echo amplitudes through transducer spacing, and adjusting diffraction characteristics through layout [14]. This flexibility allows GHz transducers to be used in a variety of configurations such as for GHz ultrasonic imaging [15], ultrasonic communication channels [16], temperature sensing [17], and clock oscillators [18]. By allowing users some choices in AlN and top dielectric layer thicknesses, more control over device operating frequencies can be realized. ...

Thermal wavefront imaging using GHz ultrasonics
  • Citing Conference Paper
  • September 2017

... Also, impediography technique has been experimented by exploiting aluminum nitride (AlN) piezoelectric thin films working at frequencies higher than 1 GHz [109]. Images of fingerprint rubber phantoms were collected by swiping the phantom itself across a 64 element linear array [110,111]. The capability of such transducer of discriminating among several loads has been demonstrated as well. ...

Wideband material detection for spoof resistance in GHz ultrasonic fingerprint sensing
  • Citing Conference Paper
  • September 2017