Photolithographic micropatterning of organic, flexible biomaterials and its applications

A current trend in biodevices has involved a shift from traditional rigid platforms to flexible and stretchable formats. These flexible devices are expected to have a significant impact on future healthcare, disease diagnostics and therapeutics. However, the fabrication of such flexible devices has been limited by the choice of materials. Biomimetic composites of naturally derived and synthetic polymers provide exciting opportunities to develop mechanically flexible, physiologically compliant, and degradable bioelectronic systems. Advantages include the ability to provide conformal contact at non-planar biointerfaces, being able to be degraded at controllable rate, and invoking minimal reactions within the body. These factors present great potential as implantable devices for in-vivo applications, while also addressing concerns with “electronic waste” by being intrinsically degradable. In this work, we present a combination of photo-crosslinkable silk proteins and conductive polymers to precisely fabricate flexible devices and cell culture substrate. A facile and scalable photolithography is applied to fabricate flexible substrates with conductive and non- conductive micropatterns which show tuneable electrical and mechanical properties. We also demonstrate an approach to engineer flexibility in materials through the creation of patterned defects inspired from Kirigami- the Japanese art of paper cutting. Mechanically flexible, free- standing, optically transparent, large-area biomaterial sheets with precisely defined and computationally designed microscale cuts can be formed using a single-step photolithographic process. As composites with conducting polymers, flexible, intrinsically electroactive sheets can be formed. Through this work, the possibility of making next- generation, fully organic, flexible bioelectronics is explored.https://scholarscompass.vcu.edu/gradposters/1099/thumbnail.jp

NiO-based electronic flexible devices

Personal, portable, and wearable electronics have become items of extensive use in daily life. Their fabrication requires flexible electronic components with high storage capability or with continuous power supplies (such as solar cells). In addition, formerly rigid tools such as electrochromic windows find new utilizations if they are fabricated with flexible characteristics. Flexibility and performances are determined by the material composition and fabrication procedures. In this regard, low-cost, easy-to-handle materials and processes are an asset in the overall production processes and items fruition. In the present mini-review, the most recent approaches are described in the production of flexible electronic devices based on NiO as low-cost material enhancing the overall performances. In particular, flexible NiO-based all-solid-state supercapacitors, electrodes electrochromic devices, temperature devices, and ReRAM are discussed, thus showing the potential of NiO as material for future developments in opto-electronic devices

Flexible Devices for Arctic Ecosystems Observations

Source at http://ojs.bibsys.no/index.php/NIK/article/view/435.Devices for observing the environment range from basic sensor systems, like step-counters, through wild-life cameras, with limited processing capabilities, to more capable devices with significant processing, memory and storage resources. Individual usage domains can benefit from a range of functionalities in these devices including flexibility in prototyping, on- device analytics, network roaming, reporting of data, and keeping the devices and services available in spite of failures and disconnections. The problem is that either the devices are too resource limited to support the range of functionalities, or they use too much energy. An important usage domain is COAT – Climate-Ecological Obser- vatory for Arctic Tundra. Presently, best practice includes deploying wild-life cameras in the Arctic Tundra, and visiting them to manually collect the recorded observations. This is a problem because such devices can only be rarely visited, and manual approaches to fetching data and storing it do not scale with regards to number of cameras, handling of human mistakes, and with freshness of observations. We present a prototype for observing the environment composed of a general purpose computer, a Raspberry PI, in combination with an ARM-based microcontroller. The combination enables us to create a more energy efficient prototype while supporting the needed functionality. The prototype improves on currently applied methods of observing the Arctic tundra. The prototype automatically observes the arctic tundra through camera, humidity and temperature sensors. It monitors itself for failures. The data is stored locally on the prototype until it can be automatically reports to a backend service over a wireless network. We have conducted experiments that show that task scheduling can reduce power consumption, and we identify some additional points that need to be addressed before we can run the device for long periods on battery power.</p

Flexible Devices for Arctic Ecosystems Observations

Devices for observing the environment range from basic sensor systems, like step-counters, through wild-life cameras, with limited processing capabilities, to more capable devices with significant processing, memory and storage resources. Individual usage domains can benefit from a range of functionalities in these devices including flexibility in prototyping, on- device analytics, network roaming, reporting of data, and keeping the devices and services available in spite of failures and disconnections. The problem is that either the devices are too resource limited to support the range of functionalities, or they use too much energy. An important usage domain is COAT – Climate-Ecological Obser- vatory for Arctic Tundra. Presently, best practice includes deploying wild-life cameras in the Arctic Tundra, and visiting them to manually collect the recorded observations. This is a problem because such devices can only be rarely visited, and manual approaches to fetching data and storing it do not scale with regards to number of cameras, handling of human mistakes, and with freshness of observations. We present a prototype for observing the environment composed of a general purpose computer, a Raspberry PI, in combination with an ARM-based microcontroller. The combination enables us to create a more energy efficient prototype while supporting the needed functionality. The prototype improves on currently applied methods of observing the Arctic tundra. The prototype automatically observes the arctic tundra through camera, humidity and temperature sensors. It monitors itself for failures. The data is stored locally on the prototype until it can be automatically reports to a backend service over a wireless network. We have conducted experiments that show that task scheduling can reduce power consumption, and we identify some additional points that need to be addressed before we can run the device for long periods on battery power

Oxide thin film transistors for flexible devices

Much attention has been gathered to flexible devices which will surely change our life style drastically. There are many kinds of flexible devices such as flexible display or medical chart. In order to realize the flexible devices, oxide thin film is one of the promising material. Because oxide film has several features which are not observed in conventional silicon materials. They are low fabrication temperature, high electrical performance or unique optical properties. To realize flexible devices with oxide thin film, several key issues should be discussed. In this talk, we will introduce several new techniques which are now being developed in our laboratory. We study the fabrication method of high performance oxide thin film transistors by using solution processed InZnO. High mobility and highly reliable TFT was demonstrated using spin coating method. In this technique, there was a problem of larger fluctuation of the performance. To solve this problem, we introduced wet annealing after the TFT fabrication and achieved very low fluctuation of the electrical performance such as mobility of threshold voltage. We apply this solution processed InZnO to logic circuit such as invertor or ring oscillators. We could demonstrate clear invertor operation or high frequency circuit operations. We demonstrate ELA on a-IGZO TFTs passivated with a hybrid passivation layer (Fig.1). The hybrid passivation layer, based on polysilsesquioxane (PSQ), is transparent and fabricated by solution process. The PSQ passivated a-IGZO TFTs has a bottom gate top contact structure. The channel used is a 70 nm thick a-IGZO (2217) deposited at room temperature by RF magnetron sputtering. Highly doped n-type Si with 100 nm thermally oxidized SiO2 layer were used as the gate and gate insulator, respectively. A stack of 80 nm Mo and 20 nm Pt deposited by RF magnetron sputtering were used as source/drain electrodes. PSQ passivated TFTs were subjected to either 248 nm KrF ELA or 308 nm XeCl ELA at room temperature and atmospheric pressure. KrF ELA was performed under ambient atmosphere while XeCl ELA was performed under N2 environment. Note that ELA was performed after the passivation coating process. Since the PSQ passivation is transparent, we expect that the incident beam will be absorbed throughout the channel. Irradiating Me 100 samples with 90-110 mJ/cm2 XeCl ELA and Me 60/Ph 40 samples with 80 mJ/cm2 KrF ELA greatly improved the transfer characteristics and mobility (~13-18 cm2/Vs) (Fig.2). Please click Additional Files below to see the full abstract

Smart decentralised energy management

The German–Finnish research project FUture Smart Energy shows, how flexible devices, consuming or producing electricity in electric grids, can be self-organised in a fully decentralised way, using autonomous algorithms integrated with the devices\u27 controllers. By shifting operation time, existing flexible devices are hereby utilised as ‘virtual batteries’, providing high storage capacity and power. To gain sufficient flexibility, a large number of devices like combined heat and power generators, heat pumps (HP), heaters, coolers, charging stations, pumps, household appliances and industrial plants, has to be coordinated. This results in a high system complexity for which the evaluated method provides an easy, resilient, cyber-secure and cost-effective solution. This novel technology uses a new market approach for electric energy systems. A real-time price signal is generated directly out of grid state variables, like frequency, voltage, power or current, and broadcast to the flexible devices. Without a need for central control, the flexible devices react like a natural swarm to the price signal. The system is easily and highly scalable, as adding and removing flexibilities does not imply adapting a central control system. The system can be operated parallel or in addition to existing energy markets

High performance bilayer-graphene Terahertz detectors

We report bilayer-graphene field effect transistors operating as THz broadband photodetectors based on plasma-waves excitation. By employing wide-gate geometries or buried gate configurations, we achieve a responsivity $\sim 1.2V/W (1.3 mA/W)$ and a noise equivalent power $\sim 2\times 10^{-9} W/Hz^{-1/2}$ in the 0.29-0.38 THz range, in photovoltage and photocurrent mode. The potential of this technology for scalability to higher frequencies and the development of flexible devices makes our approach competitive for a future generation of THz detection systems.Comment: 8 pages, 5 figures. Submitted to Applied Physics Letter

Distributed coordination of flexible devices in power networks

The penetration of new types of devices, such as domestic storage and electric vehicles, offers increasing flexibility on demand side. This will bring both new opportunities and challenges to the operation of power systems. The aim of this thesis is to design novel distributed control strategies for large scale coordination of flexible devices. To this end, flexible devices are modelled as self-interested rational agents that aim at minimizing their individual costs in response to the broadcast price signals. This thesis mainly consists of three parts, considering that the price signals can be designed in different forms, and that flexible devices could operate in different markets (e.g. energy markets, and integrated energy and reserve markets). The first part presents a multi-agent framework for the coordination of large populations of micro-storage devices in energy markets, under the assumption that the electricity price is some monotone increasing function of total power demand. The second part extends the work of the first part through taking into account the topology of power networks: the proposed modelling framework envisages heterogeneous groups of loads that operate at different buses, connected by transmission lines of limited capacity. The locational marginal prices of electricity are used as price signals, which are different in general for each bus and calculated through an optimal power flow problem. In the framework of the third part, it is envisioned that micro-storage devices and electric vehicles participate in an integrated energy-reserve market, and that they can contribute to the provision of reserve by being available to reduce their power consumption. These flexible devices autonomously schedule their operation in response to two kinds of price signals - the locational marginal prices of energy and reserve. Iterative schemes for the coordination of the flexible devices are presented in the three parts. It is proved that the proposed coordination schemes can ensure the convergence to stable market configurations, characterized as aggregative equilibria at which each device cannot further reduce its cost by unilaterally changing its power profile. Distributed implementations of these proposed control strategies are discussed, and their performance is evaluated in simulations on large scale power systems.Open Acces