Simultaneous Energy Harvesting and Hand Gesture Recognition in Large Area Monolithic Dye-Sensitized Solar Cells

Internet of Things (IoT) devices have become prevalent, embedding intelligence into our environment. It is projected that over 75 billion IoT devices will be connected by 2025 worldwide, with the majority being operated indoors. Dye-sensitized solar cells (DSSC) have recently been optimized for ambient light, having the capabilities of providing sufficient energy for self-powered IoT devices. Interaction with digital technologies, termed Human Computer Interaction (HCI), is often achieved via physical mechanisms (e.g. remote controls, cell phones) which can hinder the natural interface between users and IoT devices, a key consideration for HCI. What if the solar cell that is powering the IoT device can also recognize hand gestures which would allow the user to naturally interact with the system? Previous attempts to achieve this have necessarily employed an array of solar cell/photodiodes to detect directionality. In this work, we demonstrate that by monitoring the photocurrent output of an asymmetrically patterned monolithic (i.e., single cell) DSSC, and using machine learning, we can recognize simple hand gestures, achieving an accuracy prediction of 97.71%. This work shows that, DSSCs are the perfect choice for self-powered interactive technologies, both in terms of powering IoT devices in ambient light conditions and having aesthetic qualities that are prioritized by users. As well as powering interactive technologies, they can also provide a means of interactive control.Comment: Main body: 10 pages, 6 figures, 3 tables. Document includes supplementary info: 30 pages, 47 supplementary figure

Graphene ink laminate structures on poly(vinylidene difluoride) (PVDF) for pyroelectric thermal energy harvesting and waste heat recovery

Thermal energy can be effectively converted into electricity using pyroelectrics, which act as small scale power generator and energy harvesters providing nanowatts to milliwatts of electrical power. In this paper, a novel pyroelectric harvester based on free-standing poly­(vinylidene difluoride) (PVDF) was manufactured that exploits the high thermal radiation absorbance of a screen printed graphene ink electrode structure to facilitate the conversion of the available thermal radiation energy into electrical energy. The use of interconnected graphene nanoplatelets (GNPs) as an electrode enable high thermal radiation absorbance and high electrical conductivity along with the ease of deposition using a screen print technique. For the asymmetric structure, the pyroelectric open-circuit voltage and closed-circuit current were measured, and the harvested electrical energy was stored in an external capacitor. For the graphene ink/PVDF/aluminum system the closed circuit pyroelectric current improves by 7.5 times, the open circuit voltage by 3.4 times, and the harvested energy by 25 times compared to a standard aluminum/PVDF/aluminum system electrode design, with a peak energy density of 1.13 μJ/cm³. For the pyroelectric device employed in this work, a complete manufacturing process and device characterization of these structures are reported along with the thermal conductivity of the graphene ink. The material combination presented here provides a new approach for delivering smart materials and structures, wireless technologies, and Internet of Things (IoT) devices

Will the Internet of Things Be Perovskite Powered? Energy Yield Measurement and Real-World Performance of Perovskite Solar Cells in Ambient Light Conditions

The number of interconnected devices, often referred to as the Internet of Things (IoT), is increasing at a considerable rate. It is inevitable therefore that so too will the energy demand. IoT describes a range of technologies such as sensors, software, smart meters, wearable devices, and communication beacons for the purpose of connecting and exchanging data with other devices and systems over the internet. Often not located near a mains supply power source, these devices may be reliant on primary battery cells. To avoid the need to periodically replace these batteries, it makes sense to integrate the technologies with a photovoltaic (PV) cell to harvest ambient light, so that the technologies can be said to be self-powered. Perovskite solar cells have proven extremely efficient in low-light conditions but in the absence of ambient and low-light testing standards, or even a consensus on what is defined by “ambient light”, it is difficult to estimate the energy yield of a given PV technology in a given scenario. Ambient light harvesting is complex, subject to spectral considerations, and whether the light source is directly incident on the PV cell. Here, we present a realistic scenario-driven method for measuring the energy yield for a given PV technology in various situations in which an IoT device may be found. Furthermore, we show that laboratory-built p-i-n perovskite devices, for many scenarios, produce energy yields close to that of commercial GaAs solar cells. Finally, we demonstrate an IoT device, powered by a mesoporous carbon perovskite solar module and supercapacitor, and operating through several day–night cycles

A self-synchronized optoelectronic oscillator based on an RTD photodetector and a laser diode

We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line, and a resonant tunneling diode(RTD) free-running oscillator that is monolithic integrated with a waveguide photodetector. The RTD-OEO exhibits single-side band phase noise power below 100 dBc/Hz with more than 30-dB noise suppression at 10 kHz from the center free-running frequency for fiber loop lengths around 1.2 km. The RTD-OEO can be controlled either by the injected optical power or the fiber delay line and its power consumption is below 0.55 W. The RTD-OEO stability is achieved without using other high-speed optical/optoelectronic components and amplification

Nano patterned surfaces for biomaterial applications

Abstract. Bionanotechnology has seen much interest in the past few years. The development in new nanotechnologies and the transfer of such to biomedical applications has been received with large expectations. Here we will describe some of the most common techniques to prepare surfaces with nanometric sized features and how they have been applied to control cell behavior. The focus, however, will be on electron beam lithography and its use in biological applications. We will show that such highly ordered surfaces exhibit low adhesive properties for cells. Also, such topographies change the wetting properties to be either more hydrophilic or hydrophobic depending on the surface energy of the flat surface. Today, little research has found its way to the commercial market. This is mainly down to the ability to make large areas or large quantities of nano patterned materials. We will describe a few methods by which we think it would be possible to mass produce nano topographically patterned surfaces