Xiaotian Zou

Tapered Optical Fiber Sensor for Label-Free Detection of Biomolecules

This paper presents a fast, highly sensitive and low-cost tapered optical fiber biosensor that enables the label-free detection of biomolecules. The sensor takes advantage of the interference effect between the fiber’s first two propagation modes along the taper waist region. The biomolecules bonded on the taper surface were determined by demodulating the transmission spectrum phase shift. Because of the sharp spectrum fringe signals, as well as a relatively long biomolecule testing region, the sensor displayed a fast response and was highly sensitive. To better understand the influence of various biomolecules on the sensor, a numerical simulation that varied biolayer parameters such as thickness and refractive index was performed. The results showed that the spectrum fringe shift was obvious to be measured even when the biolayer was only nanometers thick. A microchannel chip was designed and fabricated for the protection of the sensor and biotesting. Microelectromechanical systems (MEMS) fabrication techniques were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 μm. A tapered optical fiber biosensor was fabricated and evaluated with an Immune globulin G (IgG) antibody-antigen pair.

Broadband miniature fiber optic ultrasound generator

This paper presents the design, fabrication and characterization of a broadband miniature fiber optic ultrasound generator based on photoacoustic (PA) ultrasound generation principle for biomedical ultrasound imaging and ultrasound non-destructive test (NDT) applications. A novel PA generation material, gold nanocomposite, was synthesized by directly reducing gold nanoparticles within polydimethylsiloxane (PDMS) through a one-pot protocol. The fiber optic ultrasound generator was fabricated by coating the gold nanocomposite on the tip of the optical fiber. The efficiency of the PA generation using gold nanocomposite was increased 10(5) compared to using aluminum thin film and 10(3) compared to using graphite mixed within epoxy. The ultrasound profile and the acoustic distribution have been characterized. The amplitude of the generated ultrasound signal was as high as 0.64 MPa and the bandwidth was more than 20 MHz. This paper also demonstrated its capability for ultrasound imaging of a tissue specimen.

A Miniature Fiber Optic Refractive Index Sensor Built in a MEMS-Based Microchannel

A small, highly sensitive, and electromagnetic interference (EMI)-immune refractive index (RI) sensor based on the Fabry-Perot (FP) interferometer is presented. The sensor’s FP cavity was fabricated by aligning two metal-deposited, single-mode optical fiber endfaces inside a microchannel on a silicon chip. The mirrors on the fiber endfaces were made of thermal-deposited metal films, which provided the high finesse necessary to produce a highly sensitive sensor. Microelectromechanical systems (MEMS) fabrication techniques, specifically photolithography and deep dry etching, were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 μm. The RI change within the FP cavity was determined by demodulating the transmission spectrum phase shift. The sensitivity and finesse of the transmission spectrum were controlled by adjusting the cavity length and the thickness of the deposited metal. Our experimental results showed that the sensor’s sensitivity was 665.90 nm/RIU (RI Unit), and the limit of detection was 6 × 10−6 RIU. Using MEMS fabrication techniques to fabricate these sensors could make high yield mass production a real possibility. Multiple sensors could be integrated on a single small silicon chip to simultaneously measure RI, temperature, and biomolecule targets.

Rotary ultrasonic machining of carbon fiber reinforced plastic composites: An experimental study on cutting temperature

Carbon fiber reinforced plastic composites are used in many applications due to their superior properties. Drilling is the most frequently used machining process due to the need for assembly of carbon fiber reinforced plastic parts in mechanical structures. Rotary ultrasonic machining has been successfully used in drilling carbon fiber reinforced plastic composites. Reported investigations on rotary ultrasonic machining of carbon fiber reinforced plastic cover several output variables (including cutting force, torque, surface roughness, material removal rate, fiber delamination, tool wear, and power consumption). However, there are no reported studies on cutting temperature in rotary ultrasonic machining of carbon fiber reinforced plastic. This paper presents an experimental study on cutting temperature in rotary ultrasonic machining of carbon fiber reinforced plastic using two measurement methods (thermocouple and fiber optic sensor). Comparisons between these two methods are made and relations between input variables (ultrasonic power, tool rotation speed, and feedrate) and cutting temperature are experimentally determined.

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

Abstract. 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.

NUMERICAL SIMULATION OF FIBER-OPTIC PHOTOACOUSTIC GENERATOR USING NANOCOMPOSITE MATERIAL

Photoacoustic generation using an optical fiber is a promising approach to meet the challenges in most advanced ultrasonic non-destructive testing (NDT) applications. The energy-absorption layer coated on the fiber endface plays an important role in converting the laser energy into heat and exciting the acoustic wave. The selection of the absorption material and the optimization of the structure dimension are the keys for achieving high energy-conversion efficiency. A 2D-axisymmetric finite element analysis (FEA) model was established to simulate the photoacoustic generation process using a newly developed absorption material, polydimethylsiloxane/gold nanoparticle (PDMS/Au NPs) nanocomposites, with different thicknesses and laser pulse durations. The experimental results obtained using a similar set-up show a similar trend predicted by this FEA simulation. The FEA results provide practical clues to the design of the fiber-optic photoacoustic generator.

Low-cost rapid miniature optical pressure sensors for blast wave measurements

This paper presents an optical pressure sensor based on a Fabry-Perot (FP) interferometer formed by a 45° angle polished single mode fiber and an external silicon nitride diaphragm. The sensor is comprised of two V-shape grooves with different widths on a silicon chip, a silicon nitride diaphragm released on the surface of the wider V-groove, and a 45° angle polished single mode fiber. The sensor is especially suitable for blast wave measurements: its compact structure ensures a high spatial resolution; its thin diaphragm based design and the optical demodulation scheme allow a fast response to the rapid changing signals experienced during blast events. The sensor shows linearity with the correlation coefficient of 0.9999 as well as a hysteresis of less than 0.3%. The shock tube test demonstrated that the sensor has a rise time of less than 2 µs from 0 kPa to 140 kPa.

An ultra-fast fiber optic pressure sensor for blast event measurements

Soldiers who are exposed to explosions are at risk of suffering traumatic brain injury (TBI). Since the causal relationship between a blast and TBI is poorly understood, it is critical to have sensors that can accurately quantify the blast dynamics and resulting wave propagation through a helmet and skull that are imparted onto and inside the brain. To help quantify the cause of TBI, it is important to record transient pressure data during a blast event. However, very few sensors feature the capabilities of tracking the dynamic pressure transients due to the rapid change of the pressure during blast events, while not interfering with the physical material layers or wave propagation. In order to measure the pressure transients efficiently, a pressure sensor should have a high resonant frequency and a high spatial resolution. This paper describes an ultra-fast fiber optic pressure sensor based on the Fabry–Perot principle for the application of measuring the rapid pressure changes in a blast event. A shock tube experiment performed in US Army Natick Soldier Research, Development and Engineering Center has demonstrated that the resonant frequency of the sensor is 4.12 MHz, which is relatively close to the designed theoretical value of 4.113 MHz. Moreover, the experiment illustrated that the sensor has a rise time of 120 ns, which demonstrates that the sensor is capable of observing the dynamics of the pressure transient during a blast event.

Cutting temperature in rotary ultrasonic machining of titanium: experimental study using novel Fabry-Perot fibre optic sensors

Titanium has a wide variety of applications, particularly in the aerospace industry. However, because of its low thermal conductivity and high strength, machining of titanium is very difficult. The heat generated in machining can dramatically shorten the tool life. Rotary ultrasonic machining (RUM) is a non-traditional machining process, and has been used to machine various difficult-to-machine materials. Investigations have been reported regarding effects of machining variables (including ultrasonic power, tool rotation speed, and feedrate) on several output variables in RUM, such as cutting force, torque, surface roughness, edge chipping, material removal rate, and tool wear. However, there have been few studies on cutting temperatures in RUM. This paper presents an experimental study on cutting temperature in RUM of titanium. It is the first study to utilise fibre optic temperature sensors to measure the cutting temperature in RUM. The results revealed effects of machining variables on cutting temperature in RUM, and demonstrated that Fabry-Perot (FP) fibre optic sensors offer more accurate localised measurement of temperature in RUM than thermocouples.

Miniature Fabry–Perot Fiber Optic Sensor for Intravascular Blood Temperature Measurements

This paper presents a miniature fiber optic sensor for intravascular blood temperature measurements. Based on the Fabry–Perot interferometric principle, the sensor is fabricated by using chemical etching and thermal deposition. Before the animal test, static temperature calibration experiments are performed to characterize the sensors sensitivity, linearity, and hysteresis. A swine model is selected to perform the in-vivo experiment. During the in-vivo experiment, the swine intravascular blood temperature is measured at different locations in coronary arteries to demonstrate the sensors performance. The sensors usage in the thermal angioplasty application is successfully presented by capturing the rise and drop of local intravascular blood temperature variations.