JP2015138022A - Diameter measurement method using fundamental frequency of nano-bubble excited by external excited vibration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the miniaturization of a nanobubble diameter is required in variety of fields not only in a medical field, however, there is no measurement method of the nanobubble diameter since a scattering probability of light at the 6-multiplication of the diameter not larger than 0.1 micron is decreased, and then, to provide a measurement method of the nanobubble diameter which is not affected by a size of the nanobubble diameter.SOLUTION: A probability of the collapse of a microbubble is large when the microbubble is contracted, on the hand, a probability of the collapse of a nanobubble is small, and the nanobubble vibrates in a radial direction in such an extremely-specific large non-linear form that pressure at the contraction becomes infinitive. This seems vague in diameter, however, this non-linear vibration is analyzed, and a common name such as an equivalent radius is theoretically defined. Since the equivalent radius is theoretically defined, the equivalent radius is theoretically led to a frequency of the non-linear vibration. Accordingly, the equivalent radius is obtained by measuring a frequency of the non-linear vibration.

Description

The present invention obtains the diameter of the nanobubble by knowing the frequency of the fundamental wave of the nonlinear vibration of the nanobubble.

When producing or using nanobubbles for use in the medical field or other fields, confirmation and management of the nanobubble diameter will be important. However, it can be said that there is no reasonable measurement method. At present, what is called dynamic light scattering is used, but it is in the category of laser photon statistical spectroscopy, and it is different from the random photon number distribution according to Poisson statistics of photons in the coherent state. There is no change in using “quantity” as a signal. On the other hand, from the Einstein-Stokes equation, the broadening of the spectrum by nanoparticles is wide, and the measurement will be in the domain of Fabry-Perot interferometry rather than photon statistical spectroscopy.

In the first place, the probability of light scattering decreases in proportion to the sixth power of the particle diameter as the diameter becomes smaller in the case of a minute scattering particle of 0.1 microns or less. A liquid containing only nanobubbles is transparent and has almost no scattered light.

Nanobubbles are oscillating nonlinearly at a specific frequency. The diameter when the nanobubbles expand is so large that the pressure inside the bubble is close to the external hydrostatic pressure, but the diameter when it is shrunk becomes as small as the pressure inside the bubble becomes extremely high. Due to the great vibration, the nanobubble diameter is indispensable. Since this is not enough, the name equivalent radius is theoretically defined. Since the equivalent radius is theoretically defined, it is theoretically linked to the frequency of nonlinear vibration. The only reasonable equivalent radius was obtained by measuring the frequency of the non-linear vibration and theoretically determining it from that value.
Therefore, when theoretically clarifying the relationship between the frequency of nonlinear vibration and the diameter of nanobubbles, and when measuring the vibration frequency of nanobubbles, the frequency due to the Doppler effect of random motion of nanobubbles according to the Einstein-Stokes equation Shift is a big problem. Two issues of solving this problem are the issues.

Means to solve the problem

である。Ｒ＝Ｒ（ｔ）はバブルの半径、Ｒ_０は等価半径、ρは液体の密度、ｐ_ｈは静液圧、ｐ_ｖはバブル内の蒸気圧、ｋはポリトロ−プ定数、σは表面張力、μは液体の粘性係数、Ｆ（ｔ）は外力である。The vibration of the nanobubbles in the radial direction is discussed exclusively using the Rayleigh-Plesset equation.
The Rayleigh-Plesset equation is

It is. R = R (t) is the radius of the bubble, R ₀ is equivalent radius, [rho is the density of the liquid, p _h is Seieki圧, p _v is the vapor pressure within the bubble, k is Poritoro - flop constant, sigma is the surface tension , Μ is the viscosity coefficient of the liquid, and F (t) is the external force.

となる。右辺第一項は線形振動項２σρ／Ｒ_０ ^２という量は復元力である。方程式（２）の解の基本振動角周波数をω_０とすると。

が成り立つ。この関係が課題を解決する原点である。この周波数はナノバブルの非線形振動の基本振動角周波数でもある。FIG. 1 shows the solution of the Rayleigh-Plesset equation. The dotted line is a large amplitude, the solid line is a small amplitude, and the waveform changes greatly depending on the amplitude, but the frequency does not change. When theoretically clarifying the relationship between the frequency of nonlinear vibration and the diameter of nanobubbles, the fact that the frequency does not change means that the fundamental vibration frequency of nonlinear vibration needs to be known. If the S / N ratio is sufficient, the amplitude should be small. Therefore, the Rayleigh-Plesset equation is transformed into a form suitable for handling small amplitudes.
x (t) << 1,
R (t) = R ₀ (1 + x (t))
far. External force, external excitation ultrasound F (t) = P _a sin (ωet)
And rewriting equation (1) as

It becomes. The first term on the right side is the linear vibration term 2σρ / R ₀ ² is the restoring force. If the fundamental vibration angular frequency of the solution of equation (2) is ω ₀ .

Holds. This relationship is the starting point for solving the problem. This frequency is also a fundamental vibration angular frequency of nonlinear vibration of nanobubbles.

When an external excitation ultrasonic wave is applied as an external force, the angular frequency ωe of the ultrasonic wave needs to be separated from the fundamental vibration angular frequency ω ₀ of the nanobubbles so as to be separated by a filter.
The tail of the nonlinear vibration spectrum is long. The half-frequency and second-harmonic frequencies are covered. Even if ωe / 2π is equal to or lower than the frequency of the half frequency, or higher than the frequency of the second harmonic, the fundamental vibration of the nanobubble is excited through the tail of the spectrum. Figure 3 shows the spectrum when excited with 1/2 external excitation ultrasonic frequency ωe = ω _0/2. If not shown it was .omega.e = 2 [omega ₀ is the same. This excitation controls the strength of the vibration of the nanobubbles so that the deformation from the harmonic vibration is not noticeable. That is, excitation is performed such that other than the linear term in the equation (2) can be ignored, and only the fundamental vibration angular frequency ω _{0 of the} nanobubble is extracted. FIG. 2 shows a spectrum when there is no external excitation ultrasonic wave F (t) = P _a sin (ωet).
The application of externally excited ultrasonic waves as an external force has the effect of narrowing the spectrum width of the vibration and clearing the angular frequency ω ₀ of the fundamental wave.

The problem of removing the influence of the frequency shift due to the Doppler effect is an example, but can be solved by extracting only the wave of nanobubbles moving in a plane whose normal is the main axis of the confocal imaging system.

Effect of the invention

It is hoped that the diameter of nanobubbles will be reduced in the medical field and others, but when the bubble diameter is less than 0.1 microns, the intensity of scattered light decreases in proportion to the sixth power of the bubble diameter. Observation of the bubble diameter by light is completely impossible.
The present invention observes the fundamental vibration frequency of nanobubbles and theoretically calculates the nanobubble diameter from the value of the vibration frequency of nanobubbles.
Microbubbles collapse, but nanobubbles do not collapse and have a unique nonlinear oscillation. At large amplitudes, the bubble's internal pressure is as large as the water pressure around it when it swells, but small enough to say that fusion may occur when it shrinks. The size is defined and named in the theory of fluid mechanics. It is called the equivalent radius and is also a function of the nonlinear vibration frequency. Measure the nonlinear vibration frequency to find the equivalent radius. This is the only way to ask. Transactions can only be made with an “equivalent radius”.
The problem is how to observe the frequency of waves generated by intensely moving nanobubbles in a Doppler-free manner according to the Einstein-Stokes equation. The present invention uses a confocal system to solve the problem.

Is a waveform of nonlinear vibration unique to nanobubbles. Is a nonlinear vibration spectrum unique to nanobubbles. Is the nonlinear vibration spectrum of nanobubbles excited by externally excited ultrasound. Is an embodiment relating to the apparatus.

The nanobubbles undergo non-linear vibration at a specific angular frequency ω ₀ determined by its size and other factors, and external excitation ultrasonic waves having an angular frequency ωe different from the non-linear vibration angular frequency are applied as external forces to the nanobubbles. removed nonlinear oscillation of the angular frequency omega _0, but by calculation from the values of the angular frequency omega ₀ is determine the diameter of the nano-bubbles, it is necessary to solve the problems of the time measurement of the angular frequency omega ₀ of the nanobubbles. The problem is that nanobubbles are moving randomly at high speed, and the value of angular frequency ω ₀ of nanobubbles is greatly modulated randomly by the Doppler effect, but the influence of this random modulation must be eliminated. This method of removing the influence of modulation is a mode for carrying out the invention.

FIG. 4 shows an embodiment of the present invention. Nanobubbles in nanobubbles population 3 is excited by external excitation ultrasonic 1 having an angular frequency .omega.e, they are moving in random directions at high speed while emitting ultrasonic nonlinear oscillation of angular frequency omega _0. Among the nanobubbles moving in a random direction, a velocity vector 7 is placed in a plane normal to the main axis 5 of the confocal system composed of the two planar ultrasonic detectors 6 and 16 and the ultrasonic lens 4. Only the group that has it is regarded as a measurement nanobubble group. That is, a group of nanobubbles that gives waves of the same frequency to two planar ultrasonic detectors. For identifying the nanobubble group, the electrical outputs of the detector 6 and the detector 16 are monitored by the real-time spectrum analyzer pairs 8 and 18, and only the frequency having the matched spectrum is extracted as a signal by the AND circuit 9. Then, the angular frequency ω ₀ is used in the calculator 10, and a group is formed as an expression R ₀ = (2σ ρ) ^1/2 / ω ₀ immediately obtained from the expression (3) ω ₀ ² = 2σ ρ / R ₀ ² The equivalent radius of the nanobubble is calculated.

1, external excitation ultrasonic wave 2, basic vibration angular frequency 3 of nano bubble, nano bubble group 4, convergent ultrasonic lens 5, main axes 6, 16, plane ultrasonic detector 7, in-plane velocity vector 8, 18 spectrum analyzer 9, AND circuit 10, calculator

Claims (2)

The focal point of a confocal system facing the focal point of a synthetic converging lens composed of two ultrasonic flat panel detectors and a converging lens is allowed to pass through the nanobubble group or stagnation through the focal point of a confocal system or a system equivalent to the confocal system. Means for applying ultrasonic waves to the nanobubble group and ultrasonic waves emitted by the nanobubble group by comparing two frequencies of two ultrasonic waves detected by the two ultrasonic flat detectors. Frequency measuring method comprising means for outputting a value of the frequency only when two frequencies are equal Means for applying an ultrasonic wave having a frequency near half or twice the fundamental vibration frequency of the nanobubble to the nanobubble as an external force, and the fundamental vibration frequency of the nanobubble whose amplitude is generated or grows by the application of the ultrasonic wave. A method for measuring the radius of nanobubbles, characterized by having means for observing and means for calculating the radius of the nanobubbles using a relational expression between the observed fundamental vibration frequency and the theory of fluid dynamics and the fundamental bubble frequency.

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