Dipen N. Sinha

Manipulation of diamond nanoparticles using bulk acoustic waves

We investigate the manipulation of 5 nm diamond nanoparticles in a user-defined pattern on a substrate using the acoustic radiation force associated with a bulk acoustic standing wave. Both concentric and rectangular patterns are studied and the experimental results are compared with theoretical predictions. The effect of drag force acting on a nanoparticle is evaluated and limits for particle speed and particle size that can be moved by acoustic radiation force are determined. We found good agreement between our experimental results and existing theoretical models and demonstrate that nanosized particles can be manipulated effectively by means of bulk wave acoustic radiation force.

Characterization of acoustically engineered polymer nanocomposite metamaterials using x-ray microcomputed tomography.

We demonstrate the fabrication of acoustically engineered diamond nanoparticles-based metamaterials and their internal microstructure characterization using x-ray microcomputed tomography (XμCT). The state-of-the-art technique based on the radiation force of ultrasound standing (or stationary) waves in a rectangular chamber is utilized to pattern clusters of 5-nm-diameter diamond nanoparticles in parallel planes within a three-dimensional (3D) matrix of epoxy before solidification. Gradually, the periodic pattern becomes permanent with full cure of the epoxy matrix so as to form a 3D metamaterial structure. We also show that the periodicity of the pattern can be changed by selecting a different ultrasound frequency. Furthermore, XμCT is used as a quality control tool to map the internal structure and characterize each metamaterial. The ultimate application is to use the results as a base for the development of finite-element models which take into account all the structural features to study the various metamaterial (optical, acoustical, thermal, etc.) functional properties.

Novel cylindrical, air-coupled acoustic levitation/concentration devices

A new class of devices for levitation and/or concentration of aerosols and small liquid/solid samples (up to several millimeters in diameter) in air has been developed. The novelty of these devices is their simplicity in design. These are inexpensive, low-power, and, in their simplest embodiment, do not require accurate alignment of a resonant cavity. Best of all, these can be off-the-shelf items. The devices are constructed from a hollow, cylindrical piezoelectric tube. The main design criteria requires a resonant mode of the tube to match a resonant mode of the interior air-filled cavity. Once matched, it is shown that drops of water in excess of 1 mm in diameter may be levitated inside the cylinder cavity against the force of gravity for less than 1 Watt of input electrical power. Efficient concentration/agglomeration of aerosol particles in air is also demonstrated.

Acoustic concentration of particles in piezoelectric tubes: Theoretical modeling of the effect of cavity shape and symmetry breaking

A new class of simple, highly efficient, cylindrical acoustic concentration devices has been developed based upon cylindrical (or near cylindrical) geometries [Kaduchak et al., Rev. Sci. Instrum. 73, 1332–1336 (2002)] for aerosol concentration applications. The concentrators are constructed from single PZT tubes driven at or near the breathing mode resonance. Acoustic concentration of aerosols is performed within the tube cavity. It has been found that slight modifications to the cylindrical cavity geometry can significantly increase the collection efficiency and assist in precise particle positioning. This paper analyzes the theoretical framework for the acoustic concentration of particles in these devices for various geometrical perturbations. The cavity geometries studied are (1) hollow cylindrical piezoelectric tube, (2) hollow piezoelectric tube with an inner concentric solid cylinder insert, (3) a hollow piezoelectric tube with a concentric elliptic insert which breaks the circular-cylindrical symme...

Optoelectronic measurements of picosecond electrical pulse propagation in coplanar waveguide transmission lines

Observations are presented concerning the effects of coplanar waveguide transmission lines on the propagation of picosecond electrical pulses using an optoelectronic time-domain measurement technique. Effects of various test structure design factors such as substrate thickness, thickness of transmission line metallization, discontinuity spacing, ground plane width, pulser/sampler line length, and pulser/sampler geometry on picosecond electrical pulse propagation in microwave/millimeter wave coplanar waveguide transmission lines are discussed, and schemes for minimizing the adverse effects of each of the above factors are provided. >

Determination of acoustical nonlinear parameter β of water using the finite amplitude method.

The acoustic nonlinearity of water is investigated using a variation of the finite amplitude method with harmonic generation. The finite amplitude method provides information on the coefficient of nonlinearity, β, through the ratio of the amplitude of the fundamental and that of the second harmonic. The pressure of both the fundamental, p1, and that of the second harmonic, p2, are determined experimentally at different transmitter-receiver separation distances, eliminating the need for knowledge of the sound absorption in the medium. It was found that the experimental relationship between the slope of p2(x)/p1(2)(x) and transmitter-receiver separation distance, x, follows a linear relationship only in the near-field, in good agreement with theoretical predictions. A β of 3.5±0.1 is determined for water at room temperature, in good agreement with previous results from both the isentropic equation of state and finite amplitude method.

8. Noninvasive determination of sound speed and attenuation in liquids

Abstract Swept-Frequency Acoustic Interferometry (SFAI) is a nonintrusive liquid characterization technique developed specifically for detecting and identifying liquids inside sealed munitions. The SFAI technique can rapidly (

Quantum effects on the temperature dependence of surface tension of simple liquids

An equation of general applicability is proposed to describe the surface tension of simple liquids over an extended temperature range. This equation incorporates the quantum effects on the exponent μ, which characterizes the temperature dependence of surface tension. Far from the critical region, μ decreases with increasing de Boer parameter and appears to reach a constant value μ≃1 for 4He and 3He. It is pointed out that for quantum liquids μ crosses over to the nonquantum mechanical value of μ≃1.28 as the critical point is approached. The surface tension and its temperature dependence are predicted for hydrogen isotopes such as T2, DT, D2, HT, and HD.

Nonlinear frequency mixing in a resonant cavity: Numerical simulations in a bubbly liquid

The study of nonlinear frequency mixing for acoustic standing waves in a resonator cavity is presented. Two high frequencies are mixed in a highly nonlinear bubbly liquid filled cavity that is resonant at the difference frequency. The analysis is carried out through numerical experiments, and both linear and nonlinear regimes are compared. The results show highly efficient generation of the difference frequency at high excitation amplitude. The large acoustic nonlinearity of the bubbly liquid that is responsible for the strong difference-frequency resonance also induces significant enhancement of the parametric frequency mixing effect to generate second harmonic of the difference frequency.

Fabrication of high-speed GaAs photoconductive pulse generators and sampling gates by ion implantation

An ion-implantation technique used to create high-speed photoconductive devices in semi-insulating gallium arsenide (GaAs) is described. The effects of electrical contacts, GaAs substrate material, and various implant parameters on device performance are presented. The best measured performance characteristics of sampled (correlation) waveforms are: full-width-at-half-maximum of 4.5 ps, rise time (10 to 90% of full amplitude) of 3.2 ps, and signal-to-noise ratio of approximately 50 dB (integration time is 10 ms). >