6 research outputs found
The EcoChip : a wireless multi-sensor platform for comprehensive environmental monitoring
This paper presents the EcoChip, a new system
based on state-of-the-art electro-chemical impedance (EIS)
technologies allowing the growth of single strain organisms
isolated from northern habitats. This portable system is a complete
and autonomous wireless platform designed to monitor and
cultivate microorganisms directly sampled from their natural
environment, particularly from harsh northern environments.
Using 96-well plates, the EcoChip can be used in the field for realtime monitoring of bacterial growth. Manufactured with highquality electronic components, this new EIS monitoring system is
designed to function at a low excitation voltage signal to avoid
damaging the cultured cells. The high-precision calibration
network leads to high-precision results, even in the most limiting
contexts. Luminosity, humidity and temperature can also be
monitored with the addition of appropriate sensors. Access to
robust data storage systems and power supplies is an obvious
limitation for northern research. That is why the EcoChip is
equipped with a flash memory that can store data over long
periods of time. To resolve the power issue, a low-power microcontroller and a power management unit control and supply all
electronic building blocks. Data stored in the EcoChip’s flash
memory can be transmitted through a transceiver whenever a
receiver is located within the functional transmission range. In this
paper, we present the measured performance of the system, along
with results from laboratory tests in-vitro and from two field tests.
The EcoChip has been utilized to collect bio-environemental data
in the field from the northern soils and ecosystems of
Kuujjuarapik and Puvirnituq, during two expeditions, in 2017 and
2018, respectively. We show that the EcoChip can effectively carry
out EIS analyses over an excitation frequency ranging from 750
Hz to 10 kHz with an accuracy of 2.35%. The overall power
consumption of the system was 140.4 mW in normal operating
mode and 81 µW in sleep mode. The proper development of the
isolated bacteria was confirmed through DNA sequencing,
indicating that bacteria thrive in the EcoChip’s culture wells while
the growing conditions are successfully gathered and stored
A 4.8-ÎĽVrms-Noise CMOS-Microelectrode Array With Density-Scalable Active Readout Pixels via Disaggregated Differential Amplifier Implementation
We demonstrate a 4.8-ÎĽVrms noise microelectrode array (MEA) based on the complementary-metal-oxide-semiconductor active-pixel-sensors readout technique with disaggregated differential amplifier implementation. The circuit elements of the differential amplifier are divided into a readout pixel, a reference pixel, and a column circuit. This disaggregation contributes to the small area of the readout pixel, which is less than 81 ÎĽm2. We observed neuron signals around 100 ÎĽV with 432 electrodes in a fabricated prototype chip. The implementation has technological feasibility of up to 12-ÎĽm-pitch electrode density and 6,912 readout channels for high-spatial resolution mapping of neuron network activity
Exploiting All-Programmable System on Chips for Closed-Loop Real-Time Neural Interfaces
High-density microelectrode arrays (HDMEAs) feature thousands of recording electrodes
in a single chip with an area of few square millimeters. The obtained electrode density is
comparable and even higher than the typical density of neuronal cells in cortical cultures.
Commercially available HDMEA-based acquisition systems are able to record the neural
activity from the whole array at the same time with submillisecond resolution. These devices
are a very promising tool and are increasingly used in neuroscience to tackle fundamental
questions regarding the complex dynamics of neural networks. Even if electrical or optical
stimulation is generally an available feature of such systems, they lack the capability of
creating a closed-loop between the biological neural activity and the artificial system. Stimuli
are usually sent in an open-loop manner, thus violating the inherent working basis of neural
circuits that in nature are constantly reacting to the external environment. This forbids to
unravel the real mechanisms behind the behavior of neural networks.
The primary objective of this PhD work is to overcome such limitation by creating a fullyreconfigurable
processing system capable of providing real-time feedback to the ongoing
neural activity recorded with HDMEA platforms. The potentiality of modern heterogeneous
FPGAs has been exploited to realize the system. In particular, the Xilinx Zynq All Programmable
System on Chip (APSoC) has been used. The device features reconfigurable
logic, specialized hardwired blocks, and a dual-core ARM-based processor; the synergy of
these components allows to achieve high elaboration performances while maintaining a high
level of flexibility and adaptivity. The developed system has been embedded in an acquisition
and stimulation setup featuring the following platforms:
\u2022 3\ub7Brain BioCam X, a state-of-the-art HDMEA-based acquisition platform capable of
recording in parallel from 4096 electrodes at 18 kHz per electrode.
\u2022 PlexStim\u2122 Electrical Stimulator System, able to generate electrical stimuli with
custom waveforms to 16 different output channels.
\u2022 Texas Instruments DLP\uae LightCrafter\u2122 Evaluation Module, capable of projecting
608x684 pixels images with a refresh rate of 60 Hz; it holds the function of optical
stimulation.
All the features of the system, such as band-pass filtering and spike detection of all the
recorded channels, have been validated by means of ex vivo experiments. Very low-latency
has been achieved while processing the whole input data stream in real-time. In the case
of electrical stimulation the total latency is below 2 ms; when optical stimuli are needed,
instead, the total latency is a little higher, being 21 ms in the worst case.
The final setup is ready to be used to infer cellular properties by means of closed-loop
experiments. As a proof of this concept, it has been successfully used for the clustering
and classification of retinal ganglion cells (RGCs) in mice retina. For this experiment, the
light-evoked spikes from thousands of RGCs have been correctly recorded and analyzed in
real-time. Around 90% of the total clusters have been classified as ON- or OFF-type cells.
In addition to the closed-loop system, a denoising prototype has been developed. The main
idea is to exploit oversampling techniques to reduce the thermal noise recorded by HDMEAbased
acquisition systems. The prototype is capable of processing in real-time all the input
signals from the BioCam X, and it is currently being tested to evaluate the performance in
terms of signal-to-noise-ratio improvement
A 16384-electrode 1024-channel multimodal CMOS MEA for high-throughput intracellular action potential measurements and impedance spectroscopy in drug-screening applications
Patch clamp is currently the gold standard for studying cell electrophysiology in preclinical drug discovery. Since it is a time-consuming technique, passive and active multielectrode arrays (MEAs) have been introduced for increased throughput in extracellular (ExC) in vitro measurements [1-3]. However, most of these tools cannot capture the essential features of intracellular (InC) action potentials (APs) used for studying drug toxicity. It has been shown that InC access can be achieved by highly localized electroporation [4], which allows low-impedance electrical recording of the InC voltage. While this technique was explored in recent designs [4-5], a tool that enables high-throughput InC measurements is not yet available. Impedance measurement is also used to study cell morphology, adhesion, differentiation and contractility [6]. Recent designs [1-3] already include impedance spectroscopy (IS), but their methods are not fast enough to capture in detail the contractile activity of cardiomyocytes. Since some drugs can inhibit cell beating without affecting the APs [6], ExC/InC recording and impedance measurement are complementary