Electrocorticography (ECoG) is receiving growing attention for both clinical and research applications thanks to its reduced invasiveness and ability of addressing large cortical areas. These ...benefits come with a main drawback, i.e. a limited frequency bandwidth. However, recent studies have shown that spiking activity from cortical neurons can be recorded when the ECoG grids present the following combined properties: (I) conformable substrate, (II) small neuron-sized electrodes with (III) low-impedance interfaces. We introduce here an ad-hoc designed ECoG device for investigating how electrode size, interface material composition and electrochemical properties affect the capability to record evoked and spontaneous neural signals from the rat somatosensory cortex and influence the ability to record high frequency neural signal components.Contact diameter reduction down to 8 μm was possible thanks to a specific coating of a (3,4-ethylenedioxytiophene)-poly (styrenesulfonate)-poly-(ethyleneglycol) (PEDOT-PSS-PEG) composite that drastically reduces impedance and increases electrical and ionic conductivities. In addition, the extreme thinness of the polyimide substrate (6 - 8 μm) and the presence of multiple perforations through the device ensure an effective contact with the brain surface and the free flow of cerebrospinal fluid. In-vivo validation was performed on rat somatosensory cortex.
Flexible piezoelectric sensors are now widely investigated for the implementation of highly conformable tactile systems such as electronic skin and they are based essentially on piezoelectric ...materials like PVDF and its copolymers. However, these sensing materials need long and high voltage procedure to increase their piezoelectric properties. Conversely, inorganic piezoelectric materials are difficult to grow or integrate on low temperature substrates (<;300°C). In this work we propose a ultra-thin flexible tactile sensor based on polycrystalline silicon with low temperature aluminum nitride (160°C) acting as sensing element. AlN crystals orientation and morphological properties are shown. Moreover, sensor fabrication process and electromechanical characterization are reported.
The establishment of greenhouses in space stations or during extended missions aboard spacecraft is vital for supplying fresh food to the crew and regulating the amount of carbon dioxide in an ...isolated environment, thereby enhancing their health. Nevertheless, constructing an enclosed system within highly specific conditions (such as microgravity, artificial lighting, limited space and resources) presents a series of challenges, necessitating the utilization of continuous monitoring technologies. In this regard, flexible sensors emerge as precious tools for preserving and safeguarding such delicate systems. However, the usage of plastic and inorganic materials for the fabrication of sensors poses a critical risk, since these tools are usually conceived as disposable devices. Here we present a technology based on cellulose blends to create a potential circular fabrication model to recycle the raw materials of the sensors after their lifecycle.
Polymer-based microfabrication approaches have been recently proposed as a low-cost alternative to traditional Capacitive Micromachined Ultrasonic Transducers (CMUT) fabrication methods. In most of ...the CMUT structures fabricated using such approaches, the electrodes passivation is achieved by a spin-coated polymer layer, with dielectric properties typically unsuitable to withstand the high in-cavity electrical fields. Moreover, typical layer thicknesses achievable by spin-coating bring to a significant increase of the effective gap height, inducing a very high collapse voltage and thus the need to use unpractically high operating voltages. In this paper, we investigate a process aimed at fabricating flexible CMUTs, potentially enabling high-performance, low-cost, curved, and ultra-miniaturized transducer configurations. In the proposed process, CMUT fabrication is carried out on an ultra-thin Polyimide substrate spun on a silicon wafer. The electrodes passivation is achieved by a thin SiO2 layer with excellent dielectric properties. A thin layer of SU-8 is used for the membrane fabrication and for sacrificial etch holes sealing. The devices are mechanically peeled-off from the wafer at the end of the process.
A metasurface based on a fishnet-like unit cell is designed, realized, and measured at terahertz frequencies through time-domain spectroscopy in reflection mode. While most of fishnet-like ...metasurfaces are designed in the resonant regime (i.e. with p\simeq\lambda,\ p and \lambda , being the period and the free-space wavelength), the proposed one is designed in the homogenized regime (i.e. with p\ll\lambda ). Experimental results show that the proposed metasurface exhibits very high reflectivity, which makes it particularly attractive for the design of high-gain Fabry-Perot cavity leaky-wave antennas.
The exploration of a novel substrate for green electronics sensors in precision agriculture holds immense promise. A compatible substrate would allow sensors to be directly integrated into plant ...tissues or placed in close proximity without impeding growth or causing physiological disturbances. This seamless integration would facilitate continuous and accurate monitoring of plant parameters, enabling early detection of stress, disease, or nutrient deficiencies. In this context, two novelties are proposed: the use of a flexible cellulose-based transparent biodegradable substrate and the use of a biodegradable transparent water-based cellulose-based glue for direct attachment on the leaves. Preliminary tests seem to indicate that such a system does not affect plant's health, while guaranteeing a low environmental impact.
Silicon Carbide based electronics remains the most suitable choice to replace silicon in power electronics. Especially in avionics SiC devices represent a reliable solution for reducing weight and ...size of aircraft power switching technology. However, some issues need to be solved to unleash the full potential of this kind of electronics. The most important challenge is related to the quality of the dielectric/SiC interface and to the techniques implemented to fabricate this interface. In this work, we investigate the morphological and electrical properties of low temperature dielectric films deposited on SiC substrate by using ECR-PECVD. To this end, we fabricated capacitors with silicon dioxide layer, deposited at low temperature, studying their performance with and without surface pretreatments and considering post-annealing effects at different temperatures and times.
The paper presents a wafer-level fabrication of a capacitive micromachined ultrasonic transducer (cMUT) using a wafer bonding process and interconnection technique without through silicon vias ...(TSV)/through glass vias (TGV) process. Anodic bonding technique is utilized for the fabrication and bottom electrode connections are taken by etching the structural layer of Silicon and silicon dioxide. The developed approach is reliable, repeatable and suitable for integration. An element having an array of 125 circular cMUT cell is reported having center frequency of 4.4 MHz.
Astronauts usually are forced to work in harsh environments, facing challenges related to living in microgravity conditions, operating in outer space, or even exploring planets with unknown pathogens ...and viruses. To this end, it is essential to provide astronauts easy tools to monitoring their health status with low cost and fast diagnostic methods. Indeed, undetected damages occurring at one crew member can compromise an entire mission and worst, it can cause the death for all the other crew members. In this respect, biosensors can offer valuable solutions. Among different biosensing techniques, Raman sensing can provide information on complex organic compounds like proteins, enzymes, DNA mutations etc. Here we present a low cost and totally label free Raman platform based on silver-coated zinc oxide nanostructures to reveal biomarkers and chemical alterations in human fluids like saliva or blood, without the need of sample processing.
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