High resolution 3D imaging of living cells with sub-optical wavelength phonons

Label-free imaging of living cells below the optical diffraction limit poses great challenges for optical microscopy. Biologically relevant structural information remains below the Rayleigh limit and beyond the reach of conventional microscopes. Super-resolution techniques are typically based on the nonlinear and stochastic response of fluorescent labels which can be toxic and interfere with cell function. In this paper we present, for the first time, imaging of live cells using sub-optical wavelength phonons. The axial imaging resolution of our system is determined by the acoustic wavelength (λa = λprobe/2n) and not on the NA of the optics allowing sub-optical wavelength acoustic sectioning of samples using the time of flight. The transverse resolution is currently limited to the optical spot size. The contrast mechanism is significantly determined by the mechanical properties of the cells and requires no additional contrast agent, stain or label to image the cell structure. The ability to breach the optical diffraction limit to image living cells acoustically promises to bring a new suite of imaging technologies to bear in answering exigent questions in cell biology and biomedicine

Quantifying Dry Rubber Content in Latex Solution Using an Ultrasonic Pulse

The quality of latex solution harvested from a para rubber tree is determined by the amount of dry rubber content (DRC). In this work, we propose the use of an ultrasonic pulse for quantifying the DRC in latex solution. Fresh latex solutions are acquired locally from different regions in the south of Thailand. The DRC of the solutions is evaluated for calibration purposes by the standard technique as recommended in ISO126:2005. Along with the calibration experiment, the ultrasonic pulse experiment is performed on the same set of the solutions in cylindrical tubes of different lengths. The ultrasonic pulse transverse longitudinally through the tubes which are fully contained with the latex solutions. Ultrasonic speeds and spatial attenuations for different dry rubber contents can then be obtained. Our results reveal that the ultrasonic speed and spatial attenuation are linearly proportional to the amount of dry rubber content in latex solution. Using the empirical relationship between the spatial attenuation and the DRC, we can predict the DRC with the accuracy comparable to that of the microwave-drying technique. Given the size of the tube, our setup is relatively small and can be portabl

Electrical Characterization of 65 W Cubic Sonoreactor with Horizontally Stacked Transducers

A sonoreactor was assembled with stacked lead zirconate titanate transducers. These transducers were attached on one side of a 10×10×10 cm3 chamber and driven by an integrated circuit power amplifier. The impedance of the reactor was analyzed in order to determine a matching inductance. The electrical frequency could be varied from 20 to 50 kHz and the electrical output power was adjustable up to 65 W. The highest power was obtained in the case of resonance at 31 kHz and the maximum temperature at the heat sink of the amplifier rose to 42.0ºC. Both acoustic cavitation and mechanical effects could be utilized in this sonoreactor for a variety of purposes including sonochemical synthesis, ultrasonic cleaning and microbial cell disruption

A search for laser heating of a sonoluminescing bubble

Thermodynamic arguments show that a sonoluminescing bubble that acts as a black body can absorb energy from a high power, pulsed laser beam. The mechanism for increasing the temperature of a sonoluminescing bubble is discussed and experiments with a frequency doubled, pulsed Nd:YAG laser are described. A bound for the amount of radiation absorbed is given as no evidence for heating was found at the low radiation intensity employed in the experiments

Real-time imaging of acoustic rectification

We image gigahertz surface acoustic waves normally incident on a microscopic linear array of triangular holes-a generic 'acoustic diode' geometry-with a real-time ultrafast optical technique. Spatiotemporal Fourier transforms reveal wave diffraction orders in k-space. Squared amplitude reflection and transmission coefficients for incidence on both sides of the array are evaluated and compared with numerical simulations. We thereby directly demonstrate acoustic rectification with an asymmetric structure

Three-dimensional energy channeling in the unit-cell model coupled to a spherical rotator II: unidirectional energy channeling

This work is the second one in a two-part series devoted to the analysis of complex nonlinear mechanism of energy channeling emerging in a locally resonant three-dimensional, unit-cell model, and the current paper considers unidirectional energy channeling. The considered system comprises an external mass subjected to a symmetric three-dimensional linear local potential with an internal spherical rotator. The present study specifically focuses on the analysis of three-dimensional, dissipative mechanism of irreversible (unidirectional) energy transport across mutually orthogonal directions realized in the limit of low-energy excitations. In particular, this study unveils the special transient regimes of three-dimensional partial and complete transformation of in-plane vibrations of the external element to out-of-plane vibrations. Similar to the results reported in the first part of the series, this three-dimensional energy flow is fully governed by the motion of the internal spherical rotator coupled to the external mass. Analysis of this peculiar response regime is based on regular multi-scale asymptotic analysis resulting in a reduced order dissipative slow-flow model. Results of the analysis are substantiated by the numerical simulations of the full model.by K. R. Jayaprakash and Yuli Starosvetsk