Tuning of 2D rod-type photonic crystal cavity for optical modulation and impact sensing

We propose a novel way of mechanical perturbation of photonic crystal cavities for on-chip applications. We utilize the equivalence of the 2D photonic crystals with perfect electric conductor (PEC) boundary conditions to the infinite height 3D counterparts for rod type photonic crystals. Designed structures are sandwiched with PEC boundaries above and below and the perturbation of the cavity structures is demonstrated by changing the height of PEC boundary. Once a defect filled with air is introduced, the metallic boundary conditions is disturbed and the effective mode permittivity changes leading to a tuned optical properties of the structures. Devices utilizing this perturbation are designed for telecom wavelengths and PEC boundaries are replaced by gold plates during implementation. For 10 nm gold plate displacement, two different cavity structures showed a 21.5 nm and 26 nm shift in the resonant wavelength. Optical modulation with a 1.3 MHz maximum modulation frequency with a maximum power consumption of 36.81 nW and impact sensing with 20 μs response time (much faster compared to the commercially available ones) are shown to be possible

Skin-Integrated wearable systems and implantable biosensors: a comprehensive review

Biosensors devices have attracted the attention of many researchers across the world. They have the capability to solve a large number of analytical problems and challenges. They are future ubiquitous devices for disease diagnosis, monitoring, treatment and health management. This review presents an overview of the biosensors field, highlighting the current research and development of bio-integrated and implanted biosensors. These devices are micro- and nano-fabricated, according to numerous techniques that are adapted in order to offer a suitable mechanical match of the biosensor to the surrounding tissue, and therefore decrease the body’s biological response. For this, most of the skin-integrated and implanted biosensors use a polymer layer as a versatile and flexible structural support, combined with a functional/active material, to generate, transmit and process the obtained signal. A few challenging issues of implantable biosensor devices, as well as strategies to overcome them, are also discussed in this review, including biological response, power supply, and data communication.This research was funded by FCT- FUNDAÇÃO PARA A CIÊNCIA E TECNOLOGIA, grant numbers: PTDC/EMD-EMD/31590/2017 and PTDC/BTM-ORG/28168/2017

Self‐powered e‐Skin based on integrated flexible organic photovoltaics and transparent touch sensors

There is a growing interest in the large area, lightweight, low-power electronic skin (e-Skin), consisting of a multitude of sensors over conformable surfaces. The use of multifunctional sensors is always challenging, especially when their energy requirements are considered. Herein, the heterogeneous integration of custom-made flexible organic photovoltaic (OPV) cells is demonstrated with a large area touch sensor array. The OPV can offer power density of more than 0.32 μW cm−2 at 1500 lux, which is sufficient to meet the instantaneous demand of the array of touch sensors. In addition to energy harvesting, it is shown that the OPVs can perform shadow sensing for proximity and gesture recognition, which are crucial features needed in the e-Skin, particularly for safe interaction in the industrial domain. Along with pressure sensing (sensitivity of up to 0.26 kPa−1 in the range of 1–10 kPa) and spatial information, the touch sensors made of indium tin oxide and monolayer graphene have shown >70% transparency, which allow light to pass through them to reach the bottom OPV layer. With better resource management and space utilization, the presented stacked integration of transparent touch-sensing layer and OPVs can evolve into a futuristic energy-autonomous e-Skin that can “see” and “feel.

Development of sensor nodes and sensors for smart farming

The world population is continuously increasing. Smart farming is required to keep up with this development by producing more food in a sustainable way. In many new sensor solution developments, the results of the sensor itself is at the target, but the whole solution fails to meet the requirements of the agriculture sensing use cases: the developments suffer from singular approaches with a constricted view solely on the sensor, which might be exchangeable. In this article, we present a holistic approach that can help to overcome these challenges. This approach considers the whole use case, from sense, compute, and connect to power. The approach is discussed with the example of the PLANtAR project, where we develop a soil nitrate sensor and a new leaf wetness and microclimate sensor for application in a greenhouse. The resulting sensor is integrated into a sensor node and compared to a state-of-the-art system. The work shows what is needed to assess the best tradeoffs for agriculture use cases based on a horticulture application

Active Matrix Flexible Sensory Systems: Materials, Design, Fabrication, and Integration

A variety of modern applications including soft robotics, prosthetics, and health monitoring devices that cover electronic skins (e-skins), wearables as well as implants have been developed within the last two decades to bridge the gap between artificial and biological systems. During this development, high-density integration of various sensing modalities into flexible electronic devices becomes vitally important to improve the perception and interaction of the human bodies and robotic appliances with external environment. As a key component in flexible electronics, the flexible thin-film transistors (TFTs) have seen significant advances, allowing for building flexible active matrices. The flexible active matrices have been integrated with distributed arrays of sensing elements, enabling the detection of signals over a large area. The integration of sensors within pixels of flexible active matrices has brought the application scenarios to a higher level of sophistication with many advanced functionalities. Herein, recent progress in the active matrix flexible sensory systems is reviewed. The materials used to construct the semiconductor channels, the dielectric layers, and the flexible substrates for the active matrices are summarized. The pixel designs and fabrication strategies for the active matrix flexible sensory systems are briefly discussed. The applications of the flexible sensory systems are exemplified by reviewing pressure sensors, temperature sensors, photodetectors, magnetic sensors, and biosignal sensors. At the end, the recent development is summarized and the vision on the further advances of flexible active matrix sensory systems is provided

Scalable processing and integration of 2D materials and devices

Due to its truly two dimensional (2D) character and its particular lattice, single layer graphene (SLG) possesses exceptional properties: it is semimetallic, transparent, strong yet flexible... Complementary features such as the insulating character of hexagonal boron nitride (h-BN) and semiconducting properties of transition metal dichalcogenides (TMDs) enable the whole spectrum of electronic devices to be built with combinations of these 2D materials. Due to this and the ease of exfoliation with a sticky tape, a vast amount of research was sparked. The mechanical exfoliation method, however, is only suitable for novel or proof-of-concept devices. The trend nowadays in electronics is towards transparent, lightweight, flexible, embedded smart devices and sensors in everyday objects such as windows and mirrors, garments, windshields, car seats, parachutes...These demands are already met inherently by these new materials, thus the challenges remaining are within their synthesis, deposition and processing, where more scalable ways of production and device fabrication need to be developed. This thesis explores innovative approaches using established techniques that aim to bridge the gap between proof-of-concept devices and real applications of 2D materials in future commercial level technologies. Methods to create graphene and engineer its properties are employed with a special focus on scalability and adaptability towards the industry. These graphene materials have been processed using pioneering schemes to create different optoelectronic devices and sensors. The techniques employed here for synthesis, transfer and deposition, device processing and characterization of graphene and derivatives, are suitable for their use in large manufacturing and mass-production. Depending on the application envisaged, different materials are used and optimize in order to balance good performance, cost-effectiveness and suitability/scalability of the process for the specific target the device was designed for

Development Of An Accurate Benchmarking System For Microwave Breast Imaging

This thesis is a discussion of the design and implementation of benchmarking system for microwave imaging systems. The current benchmarking tools for microwave imaging setups are not adaptable. A novel method for of the development of a dielectric phantom using regression analysis is presented. This is followed by a discussion of the design of a novel sensor for the purpose of in vivo dielectric properties measurements. The goal is to provide information for microwave tomography algorithms and phantom development based on in vivo dielectric properties of breast tissues Through the progress of this research two major novel advances have been made toward producing a better microwave imaging benchmark. First, a technique for systematically developing a breast phantom using regression analysis has been developed. This defines a process for researchers to produce a phantom quickly and easily, avoiding the simple trial and error development techniques of the past. Secondly, a method for measuring dielectric constant of a material through an embedded sensor was developed. Both advances are very important in producing accurate phantoms, providing in vivo tissue properties for tomography algorithms and designing matching materials for microwave imaging

Visible light assisted organosilane assembly on mesoporous silicon films and particles

Porous silicon (PSi) is a versatile matrix with tailorable surface reactivity, which allows the processing of a range of multifunctional films and particles. The biomedical applications of PSi often require a surface capping with organic functionalities. This work shows that visible light can be used to catalyze the assembly of organosilanes on the PSi, as demonstrated with two organosilanes: aminopropyl-triethoxy-silane and perfluorodecyl-triethoxy-silane. We studied the process related to PSi films (PSiFs), which were characterized by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF-SIMS) and field emission scanning electron microscopy (FESEM) before and after a plasma patterning process. The analyses confirmed the surface oxidation and the anchorage of the organosilane backbone. We further highlighted the surface analytical potential of 13 C, 19 F and 29 Si solid-state NMR (SS-NMR) as compared to Fourier transformed infrared spectroscopy (FTIR) in the characterization of functionalized PSi particles (PSiPs). The reduced invasiveness of the organosilanization regarding the PSiPs morphology was confirmed using transmission electron microscopy (TEM) and FESEM. Relevantly, the results obtained on PSiPs complemented those obtained on PSiFs. SS-NMR suggests a number of siloxane bonds between the organosilane and the PSiPs, which does not reach levels of maximum heterogeneous condensation, while ToF-SIMS suggested a certain degree of organosilane polymerization. Additionally, differences among the carbons in the organic (non-hydrolyzable) functionalizing groups are identified, especially in the case of the perfluorodecyl group. The spectroscopic characterization was used to propose a mechanism for the visible light activation of the organosilane assembly, which is based on the initial photoactivated oxidation of the PSi matrixWe acknowledge MSC funding provided by the European Commission through FP7 grant THINFACE (ITN GA 607232) and by Ministerio de Economía y Competitividad through grant NANOPROST (RTC-2016-4776-1

System-Engineered Miniaturized Robots: From Structure to Intelligence

The development of small machines, once envisioned by Feynman decades ago, has stimulated significant research in materials science, robotics, and computer science. Over the past years, the field of miniaturized robotics has rapidly expanded with many research groups contributing to the numerous challenges inherent to this field. Smart materials have played a particularly important role as they have imparted miniaturized robots with new functionalities and distinct capabilities. However, despite all efforts and many available soft materials and innovative technologies, a fully autonomous system-engineered miniaturized robot (SEMR) of any practical relevance has not been developed yet. In this review, the foundation of SEMRs is discussed and six main areas (structure, motion, sensing, actuation, energy, and intelligence) which require particular efforts to push the frontiers of SEMRs further are identified. During the past decade, miniaturized robotic research has mainly relied on simplicity in design, and fabrication. A careful examination of current SEMRs that are physically, mechanically, and electrically engineered shows that they fall short in many ways concerning miniaturization, full-scale integration, and self-sufficiency. Some of these issues have been identified in this review. Some are inevitably yet to be explored, thus, allowing to set the stage for the next generation of intelligent, and autonomously operating SEMRs