Micro-Engineered Devices for Motion Energy Harvesting

Published versio

Multilayered Waveguides for Increasing the Gain Bandwidth of Integrated Amplifiers

Published versio

Piezoelectric wind velocity sensor based on the variation of galloping frequency with drag force

In this paper, we demonstrate a miniature energy harvesting wind velocity sensor of simple, low-cost construction, based on a single-degree-of-freedom galloping structure. The sensor consists of a prismatic bluff body with a triangular cross section attached to the free end of acantilever incorporating a commercial polyvinylidene fluoride piezoelectric film. In the wind, the bluff body causes vibration of the cantileverbased on galloping, and the piezoelectric film converts the vibration energy into an electrical signal. We have observed a negative correlationbetween the wind velocity and the vibration frequency, and we demonstrate that this relationship can be used to detect wind velocity directlywith useful accuracy. A simple theoretical model indicates that the frequency shift can be accounted for by the effect of the axial loading dueto form drag. The model shows close agreement with the experimental results. In wind tunnel tests, a prototype wind velocity sensor basedon this principle could measure wind velocities from 4.45 to 10 m/s, with the measured velocity typically being within 4% of the referencevalue obtained using a Pitot tube

A dynamic regulating mechanism for increased airflow speed range in micro piezoelectric turbines

© 2016 IEEE.The paper reports the design and fabrication of a micro-planar spring for a dynamic regulating mechanism to decrease the cut-in (start-up) airflow speed of a piezoelectric turbine. This mechanism is implemented by adjusting the magnetic coupling between the turbine rotor and a piezoelectric cantilever using the spring. Varied spring shapes and dimensions were analyzed with the finite element method (FEM) to optimize the structure. A micro spring with an ultra-low spring constant of 0.78 N/m was fabricated from titanium foil by laser machining. The spring was installed into a miniaturized air turbine to achieve the self-regulation. The cut-in speed was 2.34 m/s, showing a 30% improvement against a non-regulated turbine

Microfluidics at fibre tip for nanolitre delivery and sampling

Delivery and sampling nanolitre volumes of liquid can benefit new invasive surgical procedures. However, the dead volume and difficulty in generating constant pressure flow limits the use of small tubes such as capillaries. This work demonstrates sub-millimetre microfluidic chips assembled directly on the tip of a bundle of two hydrophobic coated 100 μm capillaries to deliver nanolitre droplets in liquid environments. Droplets are created in a specially designed nanopipette and propelled by gas through the capillary to the microfluidic chip where a passive valve mechanism separates liquid from gas, allowing their delivery. By adjusting the driving pressure and microfluidic geometry we demonstrate both partial and full delivery of 10 nanolitre droplets with 0.4 nanolitre maximum error, as well as sampling from the environment. This system will enable drug delivery and sampling with minimally invasive probes, facilitating continuous liquid biopsy for disease monitoring and in-vivo drug screening

Architecture-independent power bound for vibration energy harvesters

The maximum output power of energy harvesters driven by harmonic vibrations is well known for a range of specific harvester architectures. An architecture-independent bound based on the mechanical input-power also exists and gives a strict limit on achievable power with one mechanical degree of freedom, but is a least upper bound only for lossless devices. We report a new theoretical bound on the output power of vibration energy harvesters that includes parasitic, linear mechanical damping while still being architecture independent. This bound greatly improves the previous bound at moderate force amplitudes and is compared to the performance of established harvester architectures which are shown to agree with it in limiting cases. The bound is a hard limit on achievable power with one mechanical degree of freedom and can not be circumvented by transducer or power-electronic-interface design

Acoustic power delivery to pipeline monitoring wireless sensors

The use of energy harvesting for powering wireless sensors is made more challenging in most applications by the requirement for customi zation to each specific application environment because of specificities of the availab le energy form, such as precise location, direction and motion frequency, as well a s the temporal variation and unpredictability of the energy source. Wireless pow er transfer from dedicated sources can overcome these difficulties, and in this work, the use of targeted ultrasonic power transfer as a possible method for remote powering o f sensor nodes is investigated. A powering system for pipeline monitoring sensors is described and studied experimentally, with a pair of identical, non6inert ial piezoelectric transducers used at the transmitter and receiver. Power transmission of 18 mW (Root6Mean6Square) through 1 m of a 118 mm diameter cast iron pipe, wi th 8 mm wall thickness is demonstrated. By analysis of the delay between tran smission and reception, including reflections from the pipeline edges, a transmission speed of 1000 m/s is observed, corresponding to the phase velocity of the L(0,1) a xial and F(1,1) radial modes of the pipe structure. A reduction of power delivery with water6filling is observed, yet over 4 mW of delivered power through a fully6filled pipe i s demonstrated. The transmitted power and voltage levels exceed the requirements fo r efficient power management, including rectification at cold6starting conditions , and for the operation of low6power sensor nodes. The proposed powering technique may a llow the implementation of energy autonomous wireless sensor systems for monit oring industrial and network pipeline infrastructure

Micro motion amplification – A Review

Many motion-active materials have recently emerged, with new methods of integration into actuator components and systems-on-chip. Along with established microprocessors, interconnectivity capabilities and emerging powering methods, they offer a unique opportunity for the development of interactive millimeter and micrometer scale systems with combined sensing and actuating capabilities. The amplification of nanoscale material motion to a functional range is a key requirement for motion interaction and practical applications, including medical micro-robotics, micro-vehicles and micro-motion energy harvesting. Motion amplification concepts include various types of leverage, flextensional mechanisms, unimorphs, micro-walking /micro-motor systems, and structural resonance. A review of the research state-of-art and product availability shows that the available mechanisms offer a motion gain in the range of 10. The limiting factor is the aspect ratio of the moving structure that is achievable in the microscale. Flexures offer high gains because they allow the application of input displacement in the close vicinity of an effective pivotal point. They also involve simple and monolithic fabrication methods allowing combination of multiple amplification stages. Currently, commercially available motion amplifiers can provide strokes as high as 2% of their size. The combination of high-force piezoelectric stacks or unimorph beams with compliant structure optimization methods is expected to make available a new class of high-performance motion translators for microsystems

Continuously Rotating Energy Harvester with Improved Power Density

Published versio

Transduction Mechanisms and Power Density for MEMS Inertial Energy Scavengers

Accepted versio