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This work presents a miniaturized electromagnetic energy harvester (EMEH) based on two coils moving in a head-to-head permanent magnet tower. The two coils are separated by a set distance so that the applied force moves the EMEH from one equilibrium position to another. In this configuration, the harvester produces energy in two different working modes: when a force is applied to the moving part or when an external random acceleration is applied to the whole system. A custom test bench has been designed to characterize the behavior of this energy harvester under a variety of conditions encountered in wearable applications. Notably, at 10 Hz and 1.32 g RMS acceleration, our inertial EMEH demonstrates its capability to sustain a consistent output power of 1696 μW within a total volume of 22.39 cm3, showcasing its efficiency in environments with erratic stimuli typical of wearable and biomedical applications. The presented EMEH is compared with reported inertial EMEH structures to extract its design limitations as well as future improvements, situating the present work in a comprehensive state-of-the-art and defining a generic performance target for biomedical and wearable applications.

Colorimetric characterisation systems based on LEDs and RBG sensors are straightforward to implement, are highly integrable allowing for portable measurement systems and can be constructed using widespread and affordable components. They have already proved to be a satisfactory solution in several applications related to chemical analysis. In this paper, we present an RGB sensor-based prototype for colorimetric characterisation, which can accommodate cuvettes with optical paths of 10 mm and 40 mm. We assessed the impact of experimental condition parameters such as the variability of the analyte volume in the cuvette, as well as the presence of floating particles or deposits at the bottom of the cuvette. While these would not impact the result given by a spectrophotometer that generally has a directional light source, they must be considered in LED/RGB sensor analysers in which the light path is not tightly controlled. We demonstrated that there is a minimal sensor height above the bottom of the cuvette and a minimal analyte level (both depending on the prototype optical path length) above which the analyte volume and the presence of floating particles and deposits have no impact on the prototype output signal. Finally, based on these results, we proposed a test method for a quick dye-displacement assay, in which the reagent is a dye-loaded molecularly imprinted polymer that is poured directly into a cuvette.

In this paper, we presented a novel, compact, conceptually simple, and fully functional low-cost prototype of a pH sensor with a PANI thin film as a sensing layer. The PANI deposition process is truly low-cost; it performs from the liquid phase, does not required any specialized equipment, and comprises few processing steps. The resulting PANI layer has excellent stability, resistance to solvents, and bio- and chemical compatibility. The pH sensor’s sensing part includes only a few components such as a red-light-emitting diode (LED) as a light source, and a corresponding photodiode (PD) as a detector. Unlike other PANI-based sensors, it requires no sophisticated and expensive techniques and components such lasers to excite the PANI or spectrometry to identify the PANI color change induced by pH variation. The pH sensor is sensitive in the broad pH range of 3 to 9, which is useful for numerous practical applications. The sensor requires a tiny volume of the test specimen, as little as 55 µL. We developed a fully integrated packaging solution for the pH sensor that comprises a limited number of components. The pH sensor comprises exclusively commercial off-the-shelf (COTS) components and standard printed circuit boards. The pH sensor is assembled using standard surface mounting technology (SMT).

Metal-oxide (MOX) gas sensors commonly rely on custom packaging solution. With an ever-increasing demand for MOX gas sensors, there is a clear need for a low cost, compact and high-performance package. During normal operation, MOX sensors are heated up to a temperature in the typical range of 200-300°C. However, the generated heat must not damage or degrade any other part of the assembly. Using 3D finite elements modelling, we developed an optimal package configuration. To thermally insulate the assembly from the heated MOX sensor we have developed in-house a low thermal conductivity xerogel-epoxy composite with 22.7% by weight xerogel and a thermal conductivity of 107.9 mW m−1 K−1 which is a reduction exceeding 30% compared to commercially available epoxy. Based on the low thermal conductivity xerogel-epoxy composite, we have developed a novel packaging approach that can suit the large family of MOX sensors. The developed alternative packaging solution includes a small number of assembly steps and uses standard processes and techniques. The assembled MOX sensor is low cost and has a low power consumption, while all thermally sensitive assembly parts remain at low temperature during the system’s lifetime.

This article presents a novel low EMI technique to regulate the output voltage of fully-integrated switched capacitor Dickson type step-up DC/DC converters for SPAD arrays implemented in the Silterra 0.13 μm HV-CMOS process. SPAD sensors are extremely sensitive to EMI and therefore require careful biasing. This design utilises current sources to limit the current flow into the flying capacitors altering the converter ratio and reduces the discontinuous pulse currents associated with capacitive converters. A variable voltage-controlled reference current enables output voltage regulation. The proposed four stage converter boosts 3.3 V up to an adjustable 15 V output voltage. A typical Dickson converter regulated by frequency control and the proposed current controlled converter were designed and manufactured to compare performance. Measurements confirm that the proposed design reduces the output ripple by more than 2 V when compared to the typical converter. The inclusion of the proposed voltage regulation technique reduces EMI which enables this fully-integrated Dickson charge pump to bias sensor arrays where the noise typically produced by these converters currently restricts or prohibits their use.

Biomedical electronic implants require a power source to operate. Miniaturised implants can preclude batteries and as implant dimensions reduce further, inductive power transfer no longer becomes the optimum strategy for wireless power delivery. Wide dipole antennas are proposed as an alternative power transmitter for long and thin implants. A miniaturised bioelectronic device measuring 1 mm by 1 mm by 20 mm was fabricated, wirelessly powered and used to stimulate retinal ganglion cells to provide biological validation of its functionality. Optimised wide dipole antennas operating in the GHz range for implant depths of 5 mm to 35 mm in 5 mm steps were simulated, fabricated and measured. Saline solution was used as a biological tissue phantom for power transfer efficiency measurements. The maximum safe deliverable power to the device was 1.7 mW in simulation and 1.3 mW in measurement at power transfer efficiencies of 15% and 11% respectively. The work herein confirms that wide dipole transmitting antennas are suitable for radiative near field power transfer to long and thin implants. This power transfer technique could be used for implants that are injectable, deliverable via catheter and minimally invasive, advancing the aim to create smaller more innovative electronic implantable devices. Keywords: Wireless power transfer, Bioelectronics, Antennas, Retinal ganglion cells, Injectable, Biological tissue, Finite element method

Conventional radiological and endoscopic techniques utilizing long tubes were ineffective in visualizing the small bowel mucosa until the development of wireless capsule endoscopy (WCE). WCE is a revolutionary endoscopic technology that can diagnose the complete gastrointestinal tract. However, the existing capsule technologies are passive, and thus they cannot be navigated to or held in a specific location. The design of an active capsule will present the opportunity to move and stop a device at any targeted locations leading to numerous medical applications such as drug delivery or collecting tissue samples for examinations in the laboratory. This paper implements a new locomotion methodology for WCE systems using an electromagnetic platform. The platform produces a dynamic electromagnetic field to control the motion of the capsule. The strength and the direction of the electromagnetic field that is generated by the platform are continuously adjusted in order to maintain the equilibrium state during the capsule movement. We present the detailed design of the proposed platform with an experimental setup with polyvinyl chloride tubes and ex vivo to demonstrate the performance of the capsule motion.

In this paper, a wireless implantable sensor prototype with subcutaneous solar energy harvesting is proposed. To evaluate the performance of a flexible solar panel under skin, ex-vivo experiments are conducted under natural sunlight and artificial light sources. The results show that the solar panel covered by a 3 mm thick porcine flap can output tens of microWatts to a few milliWatts depending on the light conditions. The subcutaneous solar energy harvester is tested on different body parts, which suggests the optimal position for the harvester to implant is between neck and shoulder. A wireless implantable system powered by the subcutaneous energy harvester is presented, which consists of a power management circuit, a temperature sensor, and a Bluetooth low energy module. An application is developed for data visualization on mobile devices, which can be a gateway for future IoT-based healthcare applications. The entire device is embedded in a transparent silicone housing (38 mm × 32 mm × 4 mm), including a 7 mAh rechargeable battery for energy storage. The average power consumption of the implants is about 30 μW in a 10 min operation cycle. With the subcutaneous solar energy harvester, the self-powered operation of the implantable sensor prototype is demonstrated by long-term experimental results. Two worst-case scenarios (no exposure to light and battery depletion) are considered with ex-vivo experiment simulations.

Poor environmental conditions can lead to severe health problems. It is essential to develop effective, reliable, and fast response systems for people working in hazardous environments. This paper presents a wearable Internet of Things sensor network aimed at monitoring harmful environmental conditions for safety applications via a Lora wireless network. The proposed sensor node, called the WE-Safe node, is based on a customized sensor node, which is self-powered, low-power, and supports multiple environmental sensors. Environmental data is monitored by the sensor node in real-time and transmitted to a remote cloud server. The data can be displayed to users through a web-based application located on the cloud server and the device will alert the user via a mobile application when an emergency condition is detected. The experimental results indicate that the presented safety monitoring network works reliably using energy harvesting.

Internet of Things (IoT) is a new technological paradigm that can connect things from various fields through the Internet. For the IoT connected healthcare applications, the wireless body area network (WBAN) is gaining popularity as wearable devices spring into the market. This paper proposes a wearable sensor node with solar energy harvesting and Bluetooth low energy transmission that enables the implementation of an autonomous WBAN. Multiple sensor nodes can be deployed on different positions of the body to measure the subject's body temperature distribution, heartbeat, and detect falls. A web-based smartphone application is also developed for displaying the sensor data and fall notification. To extend the lifetime of the wearable sensor node, a flexible solar energy harvester with an output-based maximum power point tracking technique is used to power the sensor node. Experimental results show that the wearable sensor node works well when powered by the solar energy harvester. The autonomous 24 h operation is achieved with the experimental results. The proposed system with solar energy harvesting demonstrates that long-term continuous medical monitoring based on WBAN is possible provided that the subject stays outside for a short period of time in a day.

This paper presents a frequency modulation based readout circuit for the measurement of skin conductance or resistance. A charge pump based frequency-to-voltage converter circuit with adjustable sensitivity is used to convert the frequency shifts due to skin resistance changes into voltage variations. The readout circuit improves the measurement accuracy and artifact rejection in measurements of the galvanic skin response on the skin, and can be integrated with wearable physiological monitoring systems. The readout circuit is designed and fabricated using the UMC 0.18 µm CMOS technology. It occupies an area of 0.18 mm2 and consumes 11.7 mW.

The power transfer efficiency of energy harvesting systems is strongly dependent on the power conditioning circuits, especially rectifiers. The voltage drop across rectifier and its leakage current can drastically influence the efficiency. The hybrid energy harvesters impose even more severe constraints on the rectifier. The low Vth transistors and bulk regulation technique are used in this work to mitigated the voltage drop and leakage current, respectively. It has been shown that the bulk regulation stops the current leakage through body of PMOS transistor. A near zero threshold cross connected CMOS rectifier is presented in this work using the standard 180nm UMC technology and experimental analysis are carried out to evaluate the circuit performance.