Non-Invasive Millimeter-Wave Profiler for Surface Height Measurement of Photoresist Films

This work presents a low-cost non-invasive millimeter-wave surface-height measurement sensor of dielectric and polymer films on glass and quartz substrates. The surface-height profiler utilizes near-field resonance measurement technique operating at 96 GHz implemented by using a single complementary split-ring resonator (CSRR) integrated with a tailor-made WR10 rectangular waveguide. By placing a glass or quartz substrate uniformly coated with SU-8 photoresist on top of the CSRR, the thickness of the SU-8 polymer can be extracted based on the reflected and transmitted electromagnetic-wave energy interacting at the electrical boundary between the substrate and polymer film. Uniform single layers of SU-8 polymer with thicknesses from 3 to 13 μm, coated on top of glass substrate are measured and characterized. The extracted polymer-film thicknesses from the sensor in this work show an agreement of higher than 95% as compared to the commercial surface profiler instrument, while offering various advantages e.g. non-invasion, ease of measurement setup, low-cost and miniaturization

Wireless Power Transfer for Gas Pipe Inspection Robots

Wireless power transfer in metal pipes is a promising alternative to tethered exploration robots, with strong potential to enable longer operating times. Here we present experimental results, including rectification efficiency, for a prototype gas pipe inspection robot with wireless power receiver functionality

Low-Cost Microfabrication for MEMS Switches and Varactors

This paper presents a low-cost micro-fabrication technique for manufacturing RF MEMS switches and varactors without intensive cleanroom environments. The fabrication process entails only laser micro-structuring technique, noncleanroom micro-lithography, standard wet-bench and hot-film emboss of SU-8 and ADEX polymers. MEMS movable structures were fabricated out of 14-μm-thick Aluminum foils and suspended above coplanar-waveguide transmission lines, which were implemented on top Duroid substrates, via 5-μm-thick SU-8 dielectric anchors. Both MEMS structures and Duroid substrate were integrated using micro-patterned polymers, developed by using dry-film ADEX and SU-8 polymers, for a composite assembly. An average fabrication yield of higher than 60% was achieved, calculated from ten fabrication attempts. The RF measurement results show that the RF MEMS devices fabricated by using the novel micro-fabrication process have good figure-of-merits, at much lower overall fabrication costs, as compared to the devices fabricated by conventional cleanroom process, enabling it as a very good micro-fabrication process for cost-effective rapid prototyping of MEMS

Wireless Power Transfer System for Battery-Less Sensor Nodes

For the first time, the design and implementation of a fully-integrated wireless information and power transfer system, operating at 24 GHz and enabling battery-less sensor nodes, is presented in this paper. The system consists of an RF power source, a receiver antenna array, a rectifier, and a battery-less sensor node which communicates via backscatter modulation at 868 MHz. The rectifier circuits use commercially available Schottky diodes to convert the RF power to DC with a measured efficiency of up to 35%, an improvement of ten percentage points compared with previously reported results. The rectifiers and the receive antenna arrays were jointly designed and optimised, thereby reducing the overall circuit size. The battery-less sensor transmitted data to a base station realised as a GNU Radio flow running on a bladeRF Software Defined Radio module. The whole system was tested in free-space in laboratory conditions and was capable of providing sufficient energy to the sensor node in order to enable operation and wireless communication at a distance of 0.15 metres

Investigation of Implantable Antennas for Exploratory Neuroscience Studies

In this paper we present a thorough and rigorous characterisation of the dielectric properties of rat skin tissue, including statistical processing. This data is used for a proof of concept study of the design, fabrication, and measurement of lightweight, flexible, and conformable microstrip patch antennas, to later enable improved chronic neuroscience research studies

Flexible Rectennas for Wireless Power Transfer to Wearable Sensors at 24 GHz

This paper presents the design and implementation of efficient & compact flexible rectennas (antenna + rectifier) for wireless power transfer to wearable IoT sensor nodes at 24 GHz. Two different rectifier configurations i.e. shunt and voltage doubler have been analyzed for performance comparison. Experimental results of complete rectenna have also been demonstrated for conformal surfaces. The proposed flexible rectifiers is fabricated through conventional PCB manufacturing method. Measured RF-DC conversion efficiency of 31% and DC voltage of up to 2.4 V is achieved for 20 dBm input power across an optimal load resistance of 300Ω at 24 GHz

A Novel 24-GHz Miniaturized Flexible Rectifier for Wireless Energy Harvesting

In this research article, the design and fabrication of a miniaturized flexible rectifier at 24 GHz for wireless power transfer to wearables is presented. The proposed circuit consists of a shunt topology rectifier including a single stub impedance matching network. Conventional PCB fabrication technique is used for the prototyping of the proposed flexible rectifier. It has a total footprint of 5.29 cm². The proposed rectifier exhibits a good trade-off between compactness and RF-to-DC conversion efficiency. The implementation on a very thin substrate (130 µm) makes it durable for wearables applications. Experimental results of the proposed rectifier show an output DC voltage of 2.0 V across an optimal load resistance of 250 Ω and measured RF-DC conversion efficiency of 23% for an input power of 17 dBm at 24 GHz

Infrastructure Robotics Research at the University of Leeds

Increased population growth and continued urbanisation will necessitate novel, bold, and revolutionary approaches to infrastructure inspection, maintenance, and repair. This will likely be done by swarms of autonomous robotic systems. The University of Leeds is quickly establishing itself as a leader in the field by taking part in two ambitious infrastructure robotics projects - Self-Repairing Cities and Pipebots. Here we present an overview of these projects, as well as two outputs from them - an Asphalt 3D Printing drone, and a wirelessly powered pipe inspection robot