Development of multi-depth probing 3D microelectrode array to record electrophysiological activity within neural cultures

Microelectrode arrays (MEAs) play a crucial role in investigating the electrophysiological activities of neuronal populations. Although two-dimensional neuronal cell cultures have predominated in neurophysiology in monitoring in-vitro the electrophysiological activity, recent research shifted toward culture using three-dimensional (3D) neuronal network structures for developing more sophisticated and realistic neuronal models. Nevertheless, many challenges remain in the electrophysiological analysis of 3D neuron cultures, among them the development of robust platforms for investigating the electrophysiological signal at multiple depths of the 3D neurons’ networks. While various 3D MEAs have been developed to probe specific depths within the layered nervous system, the fabrication of microelectrodes with different heights, capable of probing neural activity from the surface as well as from the different layers within the neural construct, remains challenging. This study presents a novel 3D MEA with microelectrodes of different heights, realized through a multi-stage mold-assisted electrodeposition process. Our pioneering platform allows meticulous control over the height of individual microelectrodes as well as the array topology, paving the way for the fabrication of 3D MEAs consisting of electrodes with multiple heights that could be tailored for specific applications and experiments. The device performance was characterized by measuring electrochemical impedance, and noise, and capturing spontaneous electrophysiological activity from neurospheroids derived from human induced pluripotent stem cells. These evaluations unequivocally validated the significant potential of our innovative multi-height 3D MEA as an avant-garde platform for in vitro 3D neuronal studies

Paraunitary oversampled filter bank design for channel coding

Oversampled filter banks (OSFBs) have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder's synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided

Piezoelectric graphene field effect transistor pressure sensors for tactile sensing

This paper presents graphene field-effect transistor (GFET) based pressure sensors for tactile sensing. The sensing device comprises GFET connected with a piezoelectric metal-insulator-metal (MIM) capacitor in an extended gate configuration. The application of pressure on MIM generates a piezo-potential which modulates the channel current of GFET. The fabricated pressure sensor was tested over a range of 23.54–94.18 kPa, and it exhibits a sensitivity of 4.55 × 10−3 kPa−1. Further, the low voltage (∼100 mV) operation of the presented pressure sensors makes them ideal for wearable electronic applications

Time Characterization of Capacitive MEMS RF Switches

The significative technological contribute provided by capacitive MicroElectroMechanical System Radio Frequency (MEMS RF) switches has to be accompanied with state–of–the–art methodologies for accurate measurements of their performances. In this paper, after a brief review on the design of a MEMS switch, a test bench for testing its time domain and reliability features is proposed

Acoustic Source DOA Estimation using the Cross-Entropy Method (SYS 14)

This paper deals with the problem of estimating the Direction-of-Arrivals (DOAs) of multiple wideband sources using an array of sensors. While a variety of estimation techniques have been proposed in the literature, the Maximum-Likelihood (ML) DOA estimator has been shown to have superior performance under many challenging environments. In this paper, we propose a novel implementation for ML DOA estimator based on the Cross-Entropy (CE) method. Simulation result shows the CE algorithm converges to the CRB in all scenarios within several iterations and the convergence speed is insensitive to the coherence of sources compared to the Alternating Projection (AP) method

Silicon Oxide Surface Functionalization by Self-Assembled Nanolayers for Micro-Cantilever Transducers

We developed a functionalization procedure for silicon oxide surfaces used in microcantilever-based sensors dedicated to the detection of food contaminants in fluid matrices. In particular we focused on the determination of heavy metal ions and of agricultural pesticides. The surface functionalization was obtained by direct self-assembly of long chain molecules bearing at one end a complexing moiety for metal ions. The selected chelating molecule, the nitrilotriacetic acid (NTA), was immobilized onto silicon oxide surfaces using a three-step process involving the consecutive addition of an organosilane, glutaraldehyde and a NTA derivative solutions. The formation of the self-assembled nanostructure (SAN) at the surface was traced by means of quartz crystal microbalance with dissipation monitoring (QCM) measurements as a function of time. The results indicated that the functionalized molecule forms a rigid self-assembled film on silicon dioxide. Data analysis provided the layer thickness and the molecular orientation of the chemisorbed layers at the interface. The optimized procedure was tentatively applied to functionalize the silicon oxide outer surface of an array of microwells each containing four microcantilevers. Quantitative determination of the metal ions complexation at the surface was achieved adding the desired solution in the QCM measuring chamber and recording the adsorbed mass change as a function of concentration

Surface acidity of vanadyl pyrophosphate, active phase in n-butane selective oxidation

The surface acidity of two (VO)2P2O7 catalysts with similar specific activities per square meter of surface area in 1-butene selective oxidation, but different specific activities in n-butane selective oxidation, was studied by ammonia, pyridine, acetonitrile, CO, and CO2 adsorption, by ammonia temperature-programmed desorption, and by 2-propanol oxidation. The results for both catalysts indicate the presence of strong Br\uf8nsted sites attributed to surface P-OH groups and of medium strong Lewis sites attributed to V(IV) coordinatively unsaturated ions exposed on the surface. The presence of these centers was related to the (VO)2P2O7 structure itself and is fairly independent of the (VO)2P2O7 preparation method. However, in the (VO)2P2O7 prepared in an organic medium and to a lesser extent in the (VO)2P2O7 prepared in an aqueous medium, the presence of very strong Lewis sites also was observed. The enhancement of the rate of n-butane activation in the (VO)2P2O7 prepared in an organic medium was attributed to the presence of these sites. The role of the preparation method in the formation of such very strong Lewis sites also is discussed. \ua9 1986 American Chemical Society

Infrared studies of the diatomic molecules O2, N2, NO and H2 adsorbed on Fe2O3

An infrared spectroscopic study of the diatomic molecules O2, N2, NO and H2 adsorbed under different conditions on Fe2O3 has been performed. Complex patterns of absorption on both \u3b1-Fe2O3 and \u3b3-Fe2O3 activated in O2 at high temperature are assigned to vibrations of two different chemisorbed O2 species. N2 molecules do not interact with "oxygen rich" \u3b1-Fe2O3 surfaces, but give N2O- and N2O22- species when chemisorbed on evacuated surfaces. NO molecules give complex patterns of absorption, depending on the gas pressure. Three different types of nitrate structures can be identified, as well as NO, NO- and cis-N2O2 chemisorbed species. Chemisorbed water molecules are formed by contact of H2 with Fe2O3 surfaces even at room temperature. \ua9 1982