Y. L. Hao

Electrical coupling suppression and transient response improvement for a microgyroscope using ascending frequency drive with a 2-DOF PID controller

In this paper, we demonstrate a novel control strategy for the drive mode of a microgyroscope using ascending frequency drive (AFD) with an AGC-2DOF PID controller, which drives a resonator with a modulation signal not at the resonant frequency and senses the vibration signal at the resonant frequency, thus realizing the isolation between the actual mechanical response and electrical coupling signal. This approach holds the following three advantages: (1) it employs the AFD signal instead of the resonant frequency drive signal to excite the gyroscope in the drive direction, suppressing the electrical coupling from the drive electrode to the sense electrode; (2) it can reduce the noise at low frequency and resonant frequency by shifting flicker noise to the high-frequency part; (3) it can effectively improve the performance of the transient response of the closed-loop control with a 2-DOF (degree of freedom) PID controller compared with the conventional 1-DOF PID. The stability condition of the whole loop is investigated by utilizing the averaging and linearization method. The control approach is applied to drive a lateral tuning fork microgyroscope. Test results show good agreement with the theoretical and simulation results. The non-ideal electrical antiresonance peak is removed and the resonant peak height increases by approximately 10 dB over a 400 Hz span with a flicker noise reduction of 30 dB within 100 Hz using AFD. The percent overshoot is reduced from 36.2% (1DOF PID) to 8.95% (2DOF PID, about 75.3% overshoot suppression) with 15.3% improvement in setting time.

Suspended nanoscale solenoid metal inductor with tens-nH level inductance

This paper reports a novel suspended nanoscale solenoid metal inductor with inductance of several tens-nH for analog-circuit and radio-frequency application. The nanoscale inductors consist of three-dimensional aluminum or gold nanohelices, which are transformed from nanometer thick metal cantilevers by focused-ion-beam stress-introducing technology. For the inductor with a two-turn helix conductor, the inductance is measured to reach more than 20 nH while the structure size is less than 10 times 2 mum2. The quality factor is 1.4 at 100 MHz, and might increase to about several tens at Gigahertz. The inherent series resistance of the two-turn inductor is 10.6 Ohm.

Electrical coupling suppressing for a microgyroscope using ascending frequency drive with 2-DOF PID controller

This work demonstrates a novel control strategy for the drive mode of a MEMS gyroscope using ascending frequency drive with AGC-2DOF PID controller instead of resonant frequency drive. It can suppress the electrical coupling from the drive electrodes to the sense electrodes, reduce the low frequency noise and improve the transient response by using 2DOF PID controller. Test results indicate the electrical antiresonance peak is eliminated and the resonant peak height increases approximate 10dB over 400Hz span with a flicker noise reduction of 30dB within 100Hz. The percent overshoot is reduced from 36.2% (1DOF PID) to 8.95% (2DOF PID) with 15.3% improved in setting time. The scale factor is measured to be 5.6mv/deg/s with nonlinearity about 0.95% in the full range of 800deg/s.

Fabrication of Nanopillars based on Silicon Oxide Nanopatterns Synthesized in Oxygen Plasma Removal of Photoresist

We report for the first time a facile lithography-free approach for fabricating nanopillars over large areas or in patterns. The key technique of this approach is that randomly-distributed nanoscale SiO2 patterns can be synthesized on substrates simply by removing photoresist with oxygen plasma bombardment. Those SiO2 nanopatterns may further function as masks in the following etching process for nanopillars. Based on this approach, a variety of microstructures containing nanopillars with diameters of 30~200 nm, which include surface micro channels, micro-cantilever probes and nanofences, have been fabricated. This approach can be applied both to silicon and metal substrates compatible with conventional micro-electromechanical systems (MEMS) fabrication.

Sculpting nanoparticle dynamics for single-bacteria-level screening and direct binding-efficiency measurement

Particle trapping and binding in optical potential wells provide a versatile platform for various biomedical applications. However, implementation systems to study multi-particle contact interactions in an optical lattice remain rare. By configuring an optofluidic lattice, we demonstrate the precise control of particle interactions and functions such as controlling aggregation and multi-hopping. The mean residence time of a single particle is found considerably reduced from 7 s, as predicted by Kramer’s theory, to 0.6 s, owing to the mechanical interactions among aggregated particles. The optofluidic lattice also enables single-bacteria-level screening of biological binding agents such as antibodies through particle-enabled bacteria hopping. The binding efficiency of antibodies could be determined directly, selectively, quantitatively and efficiently. This work enriches the fundamental mechanisms of particle kinetics and offers new possibilities for probing and utilising unprecedented biomolecule interactions at single-bacteria level.Optical trapping is a versatile tool for biomedical applications. Here, the authors use an optofluidic lattice to achieve controllable multi-particle hopping and demonstrate single-bacteria-level screening and measurement of binding efficiency of biological binding agents through particle-enabled bacteria hopping.

Torsional frequency mixing and sensing in optomechanical resonators

In this letter, a torsional optomechanical resonator for torque sensing and torsional mechanical frequency mixing is experimentally demonstrated. The torsional mechanical resonator is embedded into a split optical racetrack resonator, which provides high sensitivity in measuring torsional mechanical motion. Using this high sensitivity, torsional mechanical frequency mixing is observed without regenerative mechanical motion. The displacement noise floor of the torsional mechanical resonator is 50 fm/Hz0.5, which demonstrates a resonant torque sensitivity of 3.58 × 10−21 N m/Hz0.5. This demonstration will benefit potential applications for on-chip RF signal modulation using optical mechanical resonators.

NEMS actuator driven by electrostatic and optical force with nano-scale resolution

We experimentally demonstrate a silicon nano-wire actuator with a nano-scale resolution and tunable actuation range. The nano-scale resolution is obtained through implementing different control regulations, including coarse tuning by the electrostatic force and precision tuning by the optical force. More specially, the optical force enabled silicon nano-wire actuator can break the classical NEMS 1/3 actuation range limit, extending the actuation range to an arbitrary limit in principle. This unique approach not only provides a simple, non-intrusive solution to the tunable air gap of NEMS devices, but also presents an ultra-sensitive optical read out of the mechanical motion.

NEMS integrated photonic system using nano-silicon-photonic circuits

This paper reports a NEMS integrated photonic system, which integrate tunable laser, optical cross correct and variable optical attenuators. The NEMS integrated photonic system is fabricated with nano-silicon-photonic fabrication technology to integrate various functions in a single silicon photonic circuit chip. The high light-confinement capability of the nano-silicon waveguides guarantees superior performance. The proposed NEMS integrated photonic system demonstrates large tuning range (45 nm), pure single-mode properties (45 dB side-mode-suppression ratio (SMSR)).

A nanomachined tunable oscillator controlled by electrostatic and optical force

We develop a miniaturized electrostatically tunable optomechanical oscillator, whose frequencies can be electrostatically tuned by as much as 10%. By taking advantage of the optical and the electrical spring, the oscillator achieves a high tuning sensitivity without resorting to mechanical tension. Particularly, the high-Q optical cavity greatly enhances the system sensitivity, making it extremely sensitive to the motional signal, which is often overwhelmed by background noise.

Nano-optomechanical static random access memory (SRAM)

This paper reports an on chip nano-optomechanical SRAM, which is integrated with light modulation system on a single silicon chip. In particular, a doubly-clamped silicon beam shows bistability due to the non-linear optical gradient force generated from a ring resonator. The memory states are assigned with two stable deformation positions, which can be switched by modulating the control lights power with the integrated optical modulator. The optical SRAM has write/read time around 120 ns, which is much faster as compared with traditional MEMS memory. Meanwhile, the write and read processes can happen concurrently without interference, which further reduces the time as compared with conventional electrical enabled SRAM.