Photoacoustic Principle Research Articles

Microfluidic Pumps with Laser Streaming from Tips of Optical Fibers and Sewing Needles

AbstractThe discovery of photoacoustic laser streaming has opened up a new avenue to manipulate and drive fluids with light, but the necessity of an in situ “launch pad” has limited its utility in real‐world microfluidic applications due to both the size constraint and the complexity of fabrication. Here, it is demonstrated that 1) a versatile microfluidic pump can be materialized by using laser streaming from an optical fiber, and 2) laser streaming can be generated from a flat metal surface without any fabrication process. In the latter case, by focusing laser on the tip of a sewing needle tip, the needle can be turned into a micropump with controllable flow direction. Additionally, high‐speed imaging of the fluid motion and computational fluid dynamics simulations to confirm the photoacoustic principle of laser streaming are employed, and it is revealed that the streaming direction is determined by the direction of strongest intensity in the divergent ultrasound wavefront. Finally, the potential of laser streaming for microfluidic and optofluidic applications is demonstrated by successfully driving fluid inside a capillary tube.

OPTO-ULTRASONIC COMMUNICATION CHANNELS

Ultrasound is widely used in various applications, such as monitoring the state of structures, biomed-ical ultrasound imaging, and information (data) transmission. Ultrasonic transceivers are one of the modern communication systems, both for short-range and remote access. Indeed, the technology of the process of transmitting information using communication channels based on ultrasonic (US) vi-brations and the physical implementation of transmission using optical fiber are widely used in con-ditions of confidentiality of data processing. At the same time, the needs of wireless and wired communication demanded the development of more advanced applications (software, hardware solutions). In particular, new challenges have arisen requiring transceivers to have high frequency, wide bandwidth and compact size. Aim. Consider the “technology – opto-ultrasonic” approach used in data transmission and reception channels. This technology involves the generation of ultrasound by a pulse using the optical-acoustic effect, followed by the reception and processing of ultrasonic vibrations. Optical ultrasonic transceivers based on the photo-acoustic (US) principle of operation have great potential, in particular, to obtain the necessary: (super high) frequency of the transmitted signal; wide bandwidth (speed); ease of use as transceivers; low manufacturing cost. Materials and methods. Various methods of spectral analysis (Fourier and Wavelet) have been in-vestigated to ensure the achievement of the above goal. Results. Compared to traditional technolo-gies of information reception and transmission, optical ultrasonic transceivers provide high-frequency communication, wide bandwidth and compact size. Conclusion. The paper investigates the methods of spectral analysis (Fourier and Wavelet) and proposes, based on these studies, possi-ble options for the implementation of optical ultrasonic transceivers that can generate ultrasonic pulses with a duration on a nanosecond scale using an ultrafast laser and receive confidential data with a high degree of security. At the same time, by combining the principle of generating photo-acoustic ultrasound with the use of optical fiber, it is possible to obtain compact and inexpensive ul-trasonic transceivers.

Optical Fiber Ultrasound Probe for Radiofrequency Ablation Temperature Monitoring: In-Vitro Results

Radiofrequency ablation (RFA) is a clinical technique which inactivates targeted biological tissues by heating to remove tumors or to cure diseases like atrial fibrillation. Temperature is a fundamental parameter for ablation dose control and treatment effect evaluation. This paper presents the design, fabrication and characterization of an all-optical fiber ultrasound temperature measurement probe. The novelty of this probe is to both generate and receive ultrasound optically through fibers. The ultrasound generation was achieved with a 425 μm multi-mode fiber based on photoacoustic (PA) principle and the receiving part applied a 125 μm single mode fiber with a Fabry-Perot (FP) interferometer on its tip. The temperature was measured through detecting the time-of-flight (TOF) of the reflected ultrasound pulses. The probe's feasibility of measuring temperature during ablation had been verified in vitro while excised bovine liver tissue was used as the ultrasound reflector.

Miniature All-Optical Angle-Focused Photoacoustic Transducer

This letter presents the design, fabrication and testing of an all-optical transducer based on a photoacoustic principle. The transducer consists of a fiber optic acoustic generator and a Fabry–Perot (FP) sensor. A lens fabricated with UV glue and Gold Nanocomposites coating were mounted on the distal end of a multimode optical fiber with 400/ $425~\mu \text{m}$ core/cladding to fabricate the generator. The lens was designed with a certain offset degree and a concaved surface to module the propagation direction and focal length of acoustic waves emitted by the generator. The FP sensor was made of PDMS between two gold layers using a single mode fiber. The validation test demonstrated promising applications in miniature space, harsh environments and even vivo tissue.

Fiber Optic Sensors Based on Photoacoustic Effect for Rebar Corrosion Measurement

An all-optical ultrasound sensing system based on photoacoustic principle is developed to monitor and investigate the initiation of early stage steel rebar corrosion in real time. The ultrasound generator was developed by small size gold nanocomposites coated optical fibers to generate 8-MHz bandwidth signals. The ultrasound receiver was applied by a fiber Bragg grating sensor. This system was employed for the first time as a disruptive approach in order to replace the application of conventional electrical-based sensors due to their unique advantages including miniature size, lightweight, immunity to electromagnetic interference, resistance to corrosion, and distributed sensing capability. Accelerated corrosion tests were conducted on steel rebars to validate the developed sensing system. The obtained results indicated that the mass loss of corroded steel rebars was characterized by the centroid frequency shift of measured ultrasound signals. The correlation between the centroid frequency shift and the mass loss depicted an exponential relationship.

Theranostics of Gold Nanoparticles with an Emphasis on Photoacoustic Imaging and Photothermal Therapy.

Gold nanoparticles (AuNPs) are promising biomedical agents in terms of both imaging and therapy, exhibiting excellent physical and chemical characteristics. The actions of AuNPs can be remotely controlled using strong near-infrared (NIR) light, associated with minimal lateral invasion. Employing the photoacoustic (PA) principle, AuNPs integrate imaging and temperature control, affording both diagnosis and treatment mediated by NIR light. We here review recent progress in the theranostic field employing AuNPs to both PA and photothermal ends.

A non-invasive photoacoustic and ultrasonic method for the measurement of glucose solution concentration

Diabetes mellitus (DM) is a chronic disease affecting nearly 400 million people worldwide. In order to manage the disease, patients need to monitor the blood glucose level by puncturing the finger several times a day, which is uncomfortable and inconvenient. We present here a potential non-invasive monitoring method based on the velocity of ultrasonic waves generated in glucose solution by the photoacoustic principal, which can recognize the glucose concentration down to 20mg/dL. In order to apply this method to warm bodies, we carefully designed the experiment and performed measurements from 30 °C to 50 °C to generate a set of calibration curves, which may be used by engineers to build devices. Most importantly, we have theoretically explained the relationship between the compressibility and the glucose concentration. Our results show that the compressibility of solution decreases with the glucose concentration, which clarified the controversy between theory and experiment results in the literature. The derived formula is generally validity, which can be used to nondestructively measure solution concentration for other types of solutions using photoacoustic principle.

Fiber optic ultrasound transmitters and their applications

Ultrasound transmitters are widely used in various applications such as medical imaging and structural health monitoring. Most recently, traditional ultrasound transmitters are challenged by modern applications which require transmitters featuring a broad bandwidth and a compact size. In order to fill the gap, novel ultrasound transmitters, which are built around photoacoustic principle and optical fibers, are developed by various researchers. Photoacoustic principle is an optical ultrasound generation mechanism which involves optical energy absorption and conversion. In this paper, the history of optical ultrasound transmitters based on photoacoustic principle is reviewed and the efficiency of the photoacoustic conversion is discussed. This paper focuses on fiber optic ultrasound transmitters which utilize photoacoustic principle on optical fibers to generate ultrasound. In addition, various applications are discussed in this paper and the unique advantages of fiber optic ultrasound transmitters are covered.

Photoacoustic Measurement and Experiment of Glucose Concentrations in an Aqueous Matrix

In the near-infrared region, we can test the blood glucose by non-invasive method. Based on this theory, combined photoacoustic principle, we had research about the simulated samples of blood glucose, measured the concentration of glucose solution. We have discussed the optimal wavelength in the near-infrared region (780-2400nm), and did the experiment repeatedly, and then analyzed data through the linear, polynomial and exponential fitting of the Generalized Least Squares, the measuring accuracy of the glucose solution had improved. These research results provide the guidance on the practice and experimental evidence for the further research of measuring.

Fiber-optic ultrasound generator using periodic gold nanopores fabricated by a focused ion beam

Ultrasound generation from an optical fiber, based on the photoacoustic principle, is a promising approach to many ultrasonic applications, specifically those requiring wide bandwidth and compact size in order to achieve high resolution as well as the capability of being operated in limited space. A fiber-optic ultrasound generator using gold nanopores is reported. The gold nanopores, having high absorption efficiency, were fabricated using a focused ion beam (FIB) on the fiber endface, which was excited by a nanosecond laser in order to generate ultrasound signals via the photoacoustic principle. Experimental results demonstrate that these wide bandwidth ultrasound signals can be generated by this compact fiber-optic ultrasound generator fabricated using a FIB.

Sensitive and Fast Gas Sensor for Wide Variety of Applications Based on Novel Differential Infrared Photoacoustic Principle

Abstract A modular sensor concept for various gas measurement applications requiring high sensitivity and fast response time is presented. The proposed differential photoacoustic detection combines the selectivity of the traditional absorption method and the high sensitivity of the novel cantilever enhanced photoacoustic detector. High precision is achieved using short optical path length resulting in fast response time and wide dynamic measurement range. An example realization for greenhouse gas flux measurement is presented.

Characterization of two novel low frequency microphones for photoacoustic gas sensors

The photoacoustic principle for measuring gas concentration is well established based upon macromechanical assembly. However, microsystem based photoacoustic could benefit from smaller size and lower cost, but needs a high resolution microphone to be competitive. Here we present the characterization of two dedicated low frequency microphones. Both microphones have been fabricated in the same MPW foundry process, but additional post processing step enabling narrow ventilation slots through membranes of multiple thickness that increase the sensitivity of microphones, has been used. Preliminary results indicate a sensitivity of 800 µV/V-Pa, sufficient for high resolution photoacoustic gas sensors.

Concomitant speed-of-sound tomography in photoacoustic imaging

We present a method to generate quantitative cross-sectional maps of acoustic propagation speed in tissue using the photoacoustic principle. The method is based on the interaction of laser-induced ultrasound from an extraneous absorber with the object under photoacoustic investigation. The propagation times of the ultrasound transients through the object at angles around 360° are measured using a multielement ultrasound detector. The geometry lends itself to fan-beam reconstruction allowing speed-of-sound tomograms to be generated. Simultaneously, conventional photoacoustic computed tomography can be performed as well. We demonstrate the concept showing results on phantoms carrying speed-of-sound distributions.

Photoacoustic gas detection for fire warning

A detector for measuring the gas concentration of carbon dioxide based on an infrared photoacoustic principle is presented. Many molecules and particles in the atmosphere cause extinction of an incident beam of infrared radiation due to absorption and scattering processes. The absorption occurs at wavelengths which are very specific for each molecule. In the miniaturized gas detector presented the ambient gas enters a small cell (approx. 1 cm 3) via a diffusion membrane. The gas is irradiated with pulsed infrared light at the specific absorption wavelength for carbon dioxide. The absorption of the radiation energy by the gas molecules causes slight variations of the pressure inside the measuring cell which can be detected with a commercial microphone. The amplified and subsequently linearized microphone signal is proportional to the gas concentration present. The applicability of the photoacoustic principle for the detection of combustion gases is discussed.