Micro-nano biosystems: silicon nanowire sensor and micromechanical wireless power receiver

Silicon Nanowire-based biosensors owe their sensitivity to the large surface area to volume ratio of the nanowires. However, presently they have only been shown to detect specific bio-markers in low-salt buffer environments. The first part of this thesis presents a pertinent next step in the evolution of these sensors by presenting the specific detection of a target analyte (NT-ProBNP) in a physiologically relevant solution such as serum. By fabrication of the nanowires down to widths of 60 nm, choosing appropriate design parameters, optimization of the silicon surface functionalization recipe and using a reduced gate oxide thickness of 5 nm; these sensors are shown to detect the NT-ProBNP bio-marker down to 2ng/ml in serum. The observed high background noise in the measured response of the sensor is discussed and removed experimentally by the addition of an extra microfabrication step to employ a differential measurement scheme. It is also shown how the modulation of the local charge density via external static electric fields (applied by on-chip patterned electrodes) pushes the sensitivity threshold by more than an order of magnitude. These demonstrations bring the silicon nanowire-based biosensor platform one step closer to being realized for point-of-care (POC) applications. In the second half of the thesis, it is demonstrated how silicon micromechanical piezoelectric resonators could be tasked to provide wireless power to such POC bio-systems. At present most sensing and actuation platforms, especially in the implantable format, are powered either via onboard battery packs which are large and need periodic replacement or are powered wirelessly through magnetic induction, which requires a proximately located external charging coil. Using energy harnessed from electric fields at distances over a meter; comprehensive distance, orientation, and power dependence for these first-generation devices is presented. The distance response is non-monotonic and anomalous due to multi-path interferences, reflections and low directivity of the power receiver. This issue is studied and evaluated using COMSOL Multiphysics simulations. It is shown that the efficiency of these devices initially evaluated at 3% may be enhanced up to 15% by accessing higher frequency modes

Micromechanical resonator driven by radiation pressure force

Radiation pressure exerted by light on any surface is the pressure generated by the momentum of impinging photons. The associated force - fundamentally, a quantum mechanical aspect of light - is usually too small to be useful, except in large-scale problems in astronomy and astrodynamics. In atomic and molecular optics, radiation pressure can be used to trap or cool atoms and ions. Use of radiation pressure on larger objects such as micromechanical resonators has been so far limited to its coupling to an acoustic mode, sideband cooling, or levitation of microscopic objects. In this Letter, we demonstrate direct actuation of a radio-frequency micromechanical plate-type resonator by the radiation pressure force generated by a standard laser diode at room temperature. Using two independent methods, the magnitude of the resonator's response to forcing by radiation pressure is found to be proportional to the intensity of the incident light.https://www.nature.com/articles/s41598-017-16063-4.epdfPublished versio

Optical Wireless Information Transfer with Nonlinear Micromechanical Resonators

Wireless transfer of information is the basis of modern communication. It includes cellular, WiFi, Bluetooth and GPS systems, all of which use electromagnetic radio waves with frequencies ranging from typically 100 MHz to a few GHz. However, several long-standing challenges with standard radio-wave wireless transmission still exist, including keeping secure transmission of data from potential compromise. Here, we demonstrate wireless information transfer using a line-of-sight optical architecture with a micromechanical element. In this fundamentally new approach, a laser beam encoded with information impinges on a nonlinear micromechanical resonator located a distance from the laser. The force generated by the radiation pressure of the laser light on the nonlinear micromechanical resonator produces a sideband modulation signal, which carries the precise information encoded in the subtle changes in the radiation pressure. Using this, we demonstrate data and image transfer with one hundred percent fidelity with a single 96 micron by 270 micron silicon resonator element in an optical frequency band. This mechanical approach relies only on the momentum of the incident photons and is therefore able to use any portion of the optical frequency banda band that is 10,000 times wider than the radio frequency band. Our line-of-sight architecture using highly scalable micromechanical resonators offers new possibilities in wireless communication. Due to their small size, these resonators can be easily arrayed while maintaining a small form factor to provide redundancy and parallelism.Comment: 6 pages, 4 figure

Wireless actuation of micromechanical resonators

The wireless transfer of power is of fundamental and technical interest, with applications ranging from the remote operation of consumer electronics and implanted biomedical devices and sensors to the actuation of devices for which hard-wired power sources are neither desirable nor practical. In particular, biomedical devices that are implanted in the body or brain require small-footprint power receiving elements for wireless charging, which can be accomplished by micromechanical resonators. Moreover, for fundamental experiments, the ultralow-power wireless operation of micromechanical resonators in the microwave range can enable the performance of low-temperature studies of mechanical systems in the quantum regime, where the heat carried by the electrical wires in standard actuation techniques is detrimental to maintaining the resonator in a quantum state. Here we demonstrate the successful actuation of micron-sized silicon-based piezoelectric resonators with resonance frequencies ranging from 36 to 120 MHz at power levels of nanowatts and distances of ~3 feet, including comprehensive polarization, distance and power dependence measurements. Our unprecedented demonstration of the wireless actuation of micromechanical resonators via electric-field coupling down to nanowatt levels may enable a multitude of applications that require the wireless control of sensors and actuators based on micromechanical resonators, which was inaccessible until now.http://nano.bu.edu/Papers_files/micronano201636.pdfPublished versio

Wireless actuation of bulk acoustic modes in micromechanical resonators

We report wireless actuation of a Lamb wave micromechanical resonator from a distance of over 1 m with an efficiency of over 15%. Wireless actuation of conventional micromechanical resonators can have broad impact in a number of applications from wireless communication and implantable biomedical devices to distributed sensor networks.Financial support from FemtoDx is acknowledged. (FemtoDx)http://nano.bu.edu/Papers_files/Wireless-APL-4961247.pdfPublished versio

Micromechanical resonator with dielectric nonlinearity

Nonlinear response of dielectric polarization to electric field in certain media is the foundation of nonlinear optics. Optically, such nonlinearities are observed at high light intensities, achievable by laser, where atomic-scale field strengths exceeding 106–108 V/m can be realized. Nonlinear optics includes a host of fascinating phenomena such as higher harmonic frequency generation, sum and difference frequency generation, four-wave mixing, self-focusing, optical phase conjugation, and optical rectification. Even though nonlinear optics has been studied for more than five decades, such studies in analogous acoustic or microwave frequency ranges are yet to be realized. Here, we demonstrate a nonlinear dielectric resonator composed of a silicon micromechanical resonator with an aluminum nitride piezoelectric layer, a material known to have a nonlinear optical susceptibility. Using a novel multiport approach, we demonstrate second and third-harmonic generation, sum and difference frequency generation, and four-wave mixing. Our demonstration of a nonlinear dielectric resonator opens up unprecedented possibilities for exploring nonlinear dielectric effects in engineered structures with an equally broad range of effects such as those observed in nonlinear optics. Furthermore, integration of a nonlinear dielectric layer on a chip-scale silicon micromechanical resonator offers tantalizing prospects for novel applications, such as ultra high harmonic generation, frequency multipliers, microwave frequency-comb generators, and nonlinear microwave signal processing.Published versio

Micromechanical microphone using sideband modulation of nonlinear resonators

We report the successful detection of an audio signal via sideband modulation of a nonlinear piezoelectric micromechanical resonator. The 270$\times$96-$\mu$m resonator was shown to be reliable in audio detection for sound intensity levels as low as ambient room noise and to have an unamplified sensitivity of 23.9 $\mu$V/Pa. Such an approach may be adapted in acoustic sensors and microphones for consumer electronics or medical equipment such as hearing aids.Comment: 5 pages, 3 figure

Conversion of Cray pointers to Fortran 90 pointers in a Ray tracing application

This report is a documentation of techniques involved in the conversion of Cray pointers to Fortran 90 pointers in a ray-tracing application. A CAD object is generated and used for ray-tracing and the output is rendered on a pixel screen. Several implementations of ray-tracing were compared. A number of simulations were made to illustrate the properties of the code raypol. Spatial sub-division methods like Grid structures and BSP are implemented with pointers. Programming aspects relating to the use of pointers in the Fortran language are discussed. Portability is improved by conversion to Fortran 90 pointers and the use of other Fortran 90 features

A Certain Structure of Bipolar Fuzzy Subrings

The role of symmetry in ring theory is universally recognized. The most directly definable universal relation in a symmetric set theory is isomorphism. This article develops a certain structure of bipolar fuzzy subrings, including bipolar fuzzy quotient ring, bipolar fuzzy ring homomorphism, and bipolar fuzzy ring isomorphism. We define (α,β)-cut of bipolar fuzzy set and investigate the algebraic attributions of this phenomenon. We also define the support set of bipolar fuzzy set and prove various important properties relating to this concept. Additionally, we define bipolar fuzzy homomorphism by using the notion of natural ring homomorphism. We also establish a bipolar fuzzy homomorphism between bipolar fuzzy subring of the quotient ring and bipolar fuzzy subring of this ring. We constituted a significant relationship between two bipolar fuzzy subrings of quotient rings under a given bipolar fuzzy surjective homomorphism. We present the construction of an induced bipolar fuzzy isomorphism between two related bipolar fuzzy subrings. Moreover, to discuss the symmetry between two bipolar fuzzy subrings, we present three fundamental theorems of bipolar fuzzy isomorphism