A self-powered single-chip wireless sensor platform

Internet of things” require a large array of low-cost sensor nodes, wireless connectivity, low power operation and system intelligence. On the other hand, wireless biomedical implants demand additional specifications including small form factor, a choice of wireless operating frequencies within the window for minimum tissue loss and bio-compatibility This thesis describes a low power and low-cost internet of things system suitable for implant applications that is implemented in its entirety on a single standard CMOS chip with an area smaller than 0.5 mm2. The chip includes integrated sensors, ultra-low-power transceivers, and additional interface and digital control electronics while it does not require a battery or complex packaging schemes. It is powered through electromagnetic (EM) radiation using its on-chip miniature antenna that also assists with transmit and receive functions. The chip can operate at a short distance (a few centimeters) from an EM source that also serves as its wireless link. Design methodology, system simulation and optimization and early measurement results are presented

The Convergence of Parametric Resonance and Vibration Energy Harvesting

Energy harvesting is an emerging technology that derives electricity from the ambient environment in a decentralised and self-contained fashion. Applications include self-powered medical implants, wearable electronics and wireless sensors for structural health monitoring. Amongst the vast options of ambient sources, vibration energy harvesting (VEH) has attracted by far the most research attention. Two of the key persisting issues of VEH are the limited power density compared to conventional power supplies and confined operational frequency bandwidth in light of the random, broadband and fast-varying nature of real vibration. The convention has relied on directly excited resonance to maximise the mechanical-to-electrical energy conversion efficiency. This thesis takes a fundamentally different approach by employing parametric resonance, which, unlike the former, its resonant amplitude growth does not saturate due to linear damping. Therefore, parametric resonance, when activated, has the potential to accumulate much more energy than direct resonance. The vibrational nonlinearities that are almost always associated with parametric resonance can offer a modest frequency widening. Despite its promising theoretical potentials, there is an intrinsic damping dependent initiation threshold amplitude, which must be attained prior to its onset. The relatively low amplitude of real vibration and the unavoidable presence of electrical damping to extract the energy render the onset of parametric resonance practically elusive. Design approaches have been devised to passively minimise this initiation threshold. Simulation and experimental results of various design iterations have demonstrated favourable results for parametric resonance as well as the various threshold-reduction mechanisms. For instance, one of the macro-scale electromagnetic prototypes (∼1800 cm3) when parametrically driven, has demonstrated around 50% increase in half power band and an order of magnitude higher peak power (171.5 mW at 0.57 ms−2) in contrast to the same prototype directly driven at fundamental resonance (27.75 mW at 0.65 ms−2). A MEMS (micro-electromechanical system) prototype with the additional threshold-reduction design needed 1 ms−2 excitation to activate parametric resonance while a comparable device without the threshold-reduction mechanism required in excess of 30 ms−2. One of the macro-scale piezoelectric prototypes operated into auto-parametric resonance has demon-strated notable further reduction to the initiation threshold. A vacuum packaged MEMS prototype demonstrated broadening of the frequency bandwidth along with higher power peak (324 nW and 160 Hz) for the parametric regime compared to when operated in room pressure (166 nW and 80 Hz), unlike the higher but narrower direct resonant peak (60.9 nW and 11 Hz in vacuum and 20.8 nW and 40 Hz in room pressure). The simultaneous incorporation of direct resonance and bi-stability have been investigated to realise multi-regime VEH. The potential to integrate parametric resonance in the electrical domains have also been numerically explored. The ultimate aim is not to replace direct resonance but rather for the various resonant phenomena to complement each other and together harness a larger region of the available power spectrum

Plasmon-exciton coupling for signal amplification and biosensing : fundamentals and application

Surface plasmon resonance (SPR) is the collective oscillation of frequency-matched free-space photons and surface electrons at a metal/dielectric interface. Their inherent sensitivity to refractive index changes and ability to couple with exciton species and enhance light-matter interaction make them ideal candidates for low-concentration analyte detection compared to conventional biosensors. The use of metal nanostructures and nanomaterials to excite SPR represents the current state-of-the-art. However, the challenges associated with repeatable synthesis of uniform nanomaterials, complex nanostructure fabrication, low SPR generation efficiency and limited understanding of the mechanism of plasmon-exciton coupling for signal amplification have motivated the search for alternative architectures and procedures. The uniform and repeatable gold nanoslit (NS) and nanoledge (NL) array architectures offers a promising route towards addressing the above issues, and hence this research attempts to take advantage of these platforms to achieve efficient SPR generation and exciton coupling for biosensing applications. The overarching scope of this dissertation extends to the design, fabrication, and optimization of metal NS and NL structures for SPR generation and sensing applications. Emphasis is placed on investigating the mechanism of optical signal enhancement arising from plasmon-exciton coupling (PEC) with particular focus on (a) exploring the role of geometry and size of the nanostructures (b) examining the influence of SPR spectral mode overlap with exciton’s absorption and/or emission energies on the overall optical signal in a NS or NL system, and (c) investigating the analytical sensitivity and signal transduction of the PEC system to biomolecular interactions. The nanoimprinting technique based on soft lithography for NS fabrication, which is used in this work for NS array fabrication, required addressing a critical issue, namely PDMS diffusion into nanoscale patterns for high aspect ratio realization. This was mitigated by curing temperature variation and incubation time to achieve 50 nm-130 nm width NS arrays with an intense, broad spectral response that red-shifts and diminishes with increasing NS width. The 50 nm width structure exhibited ~57× optical enhancement when coupled with acridine orange, a fluorescence dye, whose absorption and emission spectra closely overlaps with plasmonic spectra. A sensitive assay for detecting DNA hybridization was generated using the interaction of the selected SARS-CoV-2 ssDNA and dsDNA with AO to trigger the metachromatic behaviour of the dye to produce a strong optical signal amplification on the formation of AO-ssDNA complex and a quenched signal upon hybridization to the complementary target DNA along with a blue shift in the fluorescence of AO-dsDNA. The SARS-CoV-2 DNA hybridization assay, based on the PEC exhibited 0.21 nM sensitivity to complementary strand target, distinguished 1-, 2-, and 3-base mismatched DNA targets, reusability of ~6 x with 96% signal recovery, stable for up to 10 days at room temperature. Regarding the NL sensing platform, the principle of the sensing mechanism is based on plasmon-mediated extraordinary optical transmission (EOT) whose wavelength red-shifts with increase in refractive index (RI) at near-metal surface. The NL plasmonic-based biosensor fabricated using a patented E-beam writing method exhibited ~ 384.08 nm/RIU sensitivity, limit of detection to cardiac troponin I (TnI) at 0.079 ng/mL, 0.084 ng/mL and 0.097 ng/mL in PBS buffer, human serum, and human blood, respectively. The direct measurement of TnI in whole human blood without any purification or sample preparation step highlights the significance of the sensing platform for point-of-care detection. Thus, this work innovates (a) a tunable SPR to meet the requirement for plasmon-exciton spectral overlap for optical signal amplification, (b) the mechanism of optical enhancements due to PEC in NS arrays, and (c) a new application of PEC in NS and EOT in NL for the sensitive detection of SARS-CoV-2 DNA hybridization and cardiovascular biomarker TnI in human blood, respectively. The enhanced light-matter interactions have a broader impact beyond healthcare to light harvesting for solar cells, heat generation for cancer therapy, and photocatalysis for nanoscale reactions like water splitting

Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors

This reprint is a collection of the Special Issue "Advance in Energy Harvesters/Nanogenerators and Self-Powered Sensors" published in Nanomaterials, which includes one editorial, six novel research articles and four review articles, showcasing the very recent advances in energy-harvesting and self-powered sensing technologies. With its broad coverage of innovations in transducing/sensing mechanisms, material and structural designs, system integration and applications, as well as the timely reviews of the progress in energy harvesting and self-powered sensing technologies, this reprint could give readers an excellent overview of the challenges, opportunities, advancements and development trends of this rapidly evolving field

Magnetophotonics for sensing and magnetometry toward industrial applications

Magnetic nanostructures sustaining different types of optical modes have been used for magnetometry and label-free ultrasensitive refractive index probing, where the main challenge is the realization of compact devices that are able to transfer this technology from research laboratories to smart industry. This Perspective discusses the state-of-the-art and emerging trends in realizing innovative sensors containing new architectures and materials exploiting the unique ability to actively manipulate their optical properties using an externally applied magnetic field. In addition to the well-established use of propagating and localized plasmonic fields, in the so-called magnetoplasmonics, we identified a new potential of the all-dielectric platforms for sensing to overcome losses inherent to metallic components. In describing recent advances, emphasis is placed on several feasible industrial applications, trying to give our vision on the future of this promising field of research merging optics, magnetism, and nanotechnology

Nanostructured metallic film plasmonics: fabrication and biosensing applications

The research presented in this dissertation is interdisciplinary in nature. It covers the areas of micro- and nanofabrication, chemistry, materials science, and biological sensing. The running theme of the dissertation is the fabrication of micro- and nanostructures for use in plasmonic devices to aid in the optical detection of biomolecules. Phase I of the research focused on a bimetallic nanostructured (nanoslit) film to aid in improving the sensitivity in comparison to pure gold films. Phase II of the research investigated nanoledge structures (stair-step features) for their ability to trap biomolecules and aid in surface plasmon resonance sensing. Phase III of the research examined how to produce a fluidic dam, a microstructure with an overcut sidewall profile, which could aid in separating biological entities from the proteins of interest. Phase IV of the research assessed the use of the fluidic dam and nanoledge structures for detection of Troponin T, a biomarker used in the diagnosis of heart attacks. Phase V of the research focused on the design and microfabrication of a plasmonic device, which could study how surface plasmon resonance influences a photocurrent generated by immobilizing photosystem I in a nanoslit structure