Satyanarayan Bhuyan

Mobile acoustic streaming based trapping and 3-dimensional transfer of a single nanowire

Acoustic manipulations of single nanoscale entities were not realized before this work owing to the acoustic streaming which usually flushes a trapped entity away. Here, we demonstrate a strategy that uses mobile acoustic streaming to effectively trap and align a single nanowire within water film on substrate surface, and stably transfers a trapped nanowire through an arbitrary 3-dimensional path in the water film. The streaming is generated by a vibrating micro-probe with uniform diameter. In our experiments, a trapped nanowire is constantly on the side of the micro-probe tip, perpendicular to the micro-probe vibration, and symmetric about the micro-probe approximately.

Manipulations of silver nanowires in a droplet on a low-frequency ultrasonic stage

In this work, we report the use of a low-frequency circular ultrasonic stage to form a circular spot of silver nanowires (AgNWs) at the stage center and to radially align AgNWs on the stage surface. The manipulations are implemented within an AgNW suspension droplet at the center of the ultrasonic stage. The ultrasonic stage (50.8 mm diameter, 3.5 mm thick) operates at a flexural vibration mode symmetric about its center and has a vibration peak at the center. The AgNW suspension is formed of deionized water with AgNWs dispersed in it. The operating frequency of the ultrasonic stage is 21.3 kHz; the AgNWs have diameter of 100 nm and length of approximately 30 μm. When the ultrasonic stage vibrates properly, AgNWs on the substrate surface in the droplet may move to the stage center and form a spot or rotate to the radial direction and align radially. The spot diameter and thickness are several hundred micrometers and several micrometers, respectively. The rotation speed of a single AgNW can be up to 31°/min when the vibration velocity of the stage center is 42 mm/s (0-p) for a 40-μL droplet. After the droplet dries out by natural evaporation without ultrasound, the spot and radial alignment have little change in the size and pattern. Principle analyses show that the spot formation and radial alignment of AgNWs are caused by the acoustic streaming in the radial direction in the droplet.

Wireless drive of a piezoelectric plate by capacitorlike structure in electric resonance with an inductor

A new technique of wirelessly transmitting electric energy to piezoelectric components is explored. In the design, an ac electric field is focused to a piezoelectric plate placed between plate-shaped live and needle ground electrodes which form a capacitorlike electric field generator in series with an inductor. The transmission of electric energy is enhanced when the capacitorlike electric field generator and inductor are in electric resonance. Experimentally it has been found that the real output power delivered to the piezoelectric plate depends on the electrode pattern, vibration mode, and electrical load of the piezoelectric component and the electric field focused by the needle ground and live electrodes. When the operating frequency is close to mechanical resonance frequency of the piezoelectric plate operating in the thickness vibration mode, a maximum output power of 0.264W and energy conversion efficiency of 1.02% have been achieved with an input voltage 150Vrms and 10mm electrode separation.

Wireless drive of piezoelectric plate by focused electric field

Wireless electric energy transmission to a piezoelectric plate using focused ac electric field is explored in this work. The ac electric field is focused, by using a needle ground electrode and plate-shaped live electrode to the piezoelectric plate placed in between them. The needle ground electrode enables better transmission of electric energy. When frequency of the electric field is close to mechanical resonance frequency of the piezoelectric plate operating in the thickness vibration mode, a maximum output power of 46.10mW has been achieved with an input voltage of 150Vrms and 2cm electrode separation.

Wireless Energy Transmission to Piezoelectric Components

In this study, a new technique of transmitting electric energy wirelessly to piezoelectric components is explored. An electromagnetic wave is used to drive a piezoelectric plate, which is made of a lead zirconate titanate (PZT) ceramic material. The piezoelectric plate is poled along thickness direction. The proposed technique is based on the principle of coupling of an electromagnetic wave and mechanical resonance. When an electric field generated by AC voltage penetrates the piezoelectric plate, an attenuated voltage is obtained across the output electrodes of the piezoelectric plate. The power received by the electrical load connected to the output electrodes reaches maximum, when frequency of the electric field is close to the mechanical resonance frequencies of the piezoelectric plate. In the design, for the generation of electric field, an AC voltage with tunable frequency is connected to two brass electrodes mounted on a plastic plate with a tunable separation. The piezoelectric plate is inserted parallel at the center of the gap between the two brass electrodes. From the experiment it has been seen that the output power achieved by the piezoelectric plate depends upon various factors like the vibration mode, electrode pattern and electrical load of the piezoelectric component, and the electric field. At the resonance frequency, a maximum output power of 5.65 mW has been achieved by the piezoelectric plate operating in the thickness vibration mode, with input voltage of 150 Vrms and 4 mm gap thickness. The output power at resonance of the piezoelectric plate, operating in the thickness vibration mode, is significantly higher than that of the plate operating in the other modes like width and longitudinal vibrations.

Wireless energizing system for an automated implantable sensor.

The wireless drive of an automated implantable electronic sensor has been explored for health monitoring applications. The proposed system comprises of an automated biomedical sensing system which is energized through resonant inductive coupling. The implantable sensor unit is able to monitor the body temperature parameter and sends back the corresponding telemetry data wirelessly to the data recoding unit. It has been observed that the wireless power delivery system is capable of energizing the automated biomedical implantable electronic sensor placed over a distance of 3 cm from the power transmitter with an energy transfer efficiency of 26% at the operating resonant frequency of 562 kHz. This proposed method ensures real-time monitoring of different human body temperatures around the clock. The monitored temperature data have been compared with a calibrated temperature measurement system to ascertain the accuracy of the proposed system. The investigated technique can also be useful for monitoring other body parameters such as blood pressure, bladder pressure, and physiological signals of the patient in vivo using various implantable sensors.

Bi-directional magnetic resonance based wireless power transfer for electronic devices

In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

A compact resonace-based wireless energy transfer system for implanted electronic devices

A compact wireless energy transfer scheme for delivering power to the implantable electronic devices has been presented here. The wireless energy transfer system is built by using a printed spiral receiving resonator with a cylindrical source resonator to transfer energy wirelessly through strongly coupled magnetic resonance. Experimentally, it is found that the wireless power transfer efficiency reaches the maximum at the resonant frequency, and the efficiency decreases with the increase of the distance between the source and receiver coils. The proposed design has the significant advantage of being easier to implement for biomedical applications due to sizeable reduction in volume required on the implantable devices.

Wireless drive of a piezoelectric plate by dipole antenna

Wireless drive of a piezoelectric plate using an electric dipole antenna-like structure is explored in this work. The AC electric field, produced by plate-shaped live and ground electrodes of the antenna-like structure is transmitted to the piezoelectric plate placed at the center 6 mm away from the electrode plane. When the driving frequency is close to mechanical resonance frequency of the piezoelectric plate operating in the thickness vibration mode, a maximum output power of 3.12 mW is achieved with 1200 Vrms, 2500 cm2 each electrode area and 5 cm electrodes separation of dipole antenna-like structure. An equivalent circuit of the wirelessly driven piezoelectric plate is developed which has a current source that is different from the equivalent circuit of conventional piezoelectric plate driven by a voltage applied via lead wires. The electric field pattern is studied by finite element method to assess the field on the surface of the piezoelectric plate. The theoretical output power characteristics well agree with the experimental results. It shows that the method has potential applications in the wireless drive of small-dimension piezoelectric devices.

Droplets merging through wireless ultrasonic actuation

A new technique of droplets merging through wireless ultrasonic actuation has been proposed and experimentally investigated in this work. The proposed method is based on the principle of resonant inductive coupling and piezoelectric resonance. When a mechanical vibration is excited in a piezoelectric plate, the ultrasonic vibration transmitted to the droplets placed on its surface and induces merging. It has been observed that the merging rate of water droplets depends on the operating frequency, mechanical vibration of piezoelectric plate, separation distance between the droplets, and volume of droplets. The investigated technique of droplets merging through piezoelectric actuation is quite useful for microfluidics, chemical and biomedical engineering applications.