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Dry EEG electrodes enhance the convenience and wearability of brain computer interface (BCI) systems, but the noise induced due to the skin electrode interface reduces the signal quality compared to that of wet electrodes. In this work, we analyzed a popular dry electrode design that incorporates several ‘finger’ shaped contacts and show how the noise level can be reduced by estimating the contact...
A dedicated front-end for biofeedback neuromuscular electrical stimulation (NESM) system is proposed. For controllable dysphagia treatment, the integrated circuit (IC) provides a stimulator front-end with programmable stimulation parameters (2µA–1mA current amplitude, DC-2KHz frequency, and variable duty cycle) and an electromyogram/impedance (EMG/ETI) readout front-end with programmable gain and...
This paper reports on the design, development, and test of a compact battery-powered wireless electrocorticography (ECoG) system. The system benefits from a new design for capacitive links that allows for bidirectional data exchange between the implant unit and the external world. A stainless steel package is designed and machined to contain a rigid 8-channel microelectrode array (MEA), a main electronic...
Advancements in technology can noticeably extend the knowledge of molecular biology for several types of cell cultures. However, at present there is a lack of available systems for real-time monitoring of cell behavior in-vitro. In this paper we propose a sensor for real-time monitoring of glucose and lactate in cell cultures, with the possibility to extend the detection to other metabolites. We explore...
Visual neuroprostheses aim to modulate the activity of surviving neurons of the visual system in an effort to elicit meaningful, psychophysical percepts. These percepts aim to aid a blind recipient in the conduct of day-to-day tasks such as navigation of unfamiliar environments, avoidance of obstacles, etc. The system architecture must balance myriad engineering, safety, and performance requirements...
Conditioning and processing of biological signals represent interesting challenges for wearable electronics in health applications. Information gathering from these signals requires complex hardware circuitry and dedicated computation resources. The design of innovative analog front-end integrated circuits, combined with efficient signal processing algorithms, allows the development of platforms for...
A CMOS-based microelectrode array (MEA) with 4225 recording sites and 1024 stimulation sites and a related data acquisition system are presented. The chip provides high spatiotemporal resolution on an active area of 1 mm × 1 mm or 2 mm × 2 mm, respectively, and allows in-vitro neural tissue interfacing experiments with full imaging capability. The entire chip surface is covered by a thin high-k dielectric...
Experimental evidence for transverse stimulation of nerve cells is presented. Stimulation is initiated by a polarization current of short duration. In one example, the initial voltage is 8.5 Volt and the current lasts for only few microseconds. The stimulation process becomes irreversible after 10–50 microseconds, depending on the initial voltage. The standard cable model cannot describe the process...
An extended-gate CMOS sensor array with enzyme-immobilized microbeads for redox-potential glucose detection is demonstrated for the first time. Redox-potential detection has the possibility to achieve high accuracy because it is not affected by the buffer conditions. Despite this high-accuracy property, redox-potential detection requires a sufficient amount of enzyme, which leads to increased cost...
The dynamic brain networks forming during wakefulness and anesthetic-induced unconsciousness are investigated using time-delayed correlation and graph theoretical measures. Electrical brain activity (EEG) from 10 patients under propofol anesthesia during routine surgery is characterized using the shortest path length, λ, and clustering, c, extracted from time-delayed correlation. An increase in λ...
A complete neural recording ASIC based on Compressive Sensing (CS) is demonstrated. Implemented using efficient digital circuit, this CS technique is able to achieve 10 times data compression while consuming only 0.83uW (@0.53VDD) additional digital power per electrode. Since CS performance is strongly signal dependent, the ASIC has been tested with standard public database. The characteristic spikes...
We describe an integrated CMOS electrochemical sensor with on-chip electrodes and packaging. The CMOS chip was fabricated in a standard 0.5 µm CMOS process, and it contains potentiostat circuits with integrated array of three electrode cells. In the potentiostat circuit, we designed high performance folded cascode class-AB operational amplifiers with rail to rail input and output suitable for low...
We report on the use of catechol for the electrochemical activation of acid-functionalised single-walled carbon nanotubes immobilised on glassy carbon electrodes. Following well-published methods for catechol activation of bare glassy carbon electrodes, these studies show the efficacy of extending the method to activation of carbon nanotubes. Voltammetric scans in catechol show an increase in current...
Lack of accessible medical care in developing countries has prompted a need for low-cost point of care medical diagnostics. Paper based medical diagnostics have been demonstrated as a viable option in these areas due for their simplicity, low-cost and easy disposal. This paper presents a custom CMOS readout IC in conjunction with paper-based electrodes as electrochemical sensors as a low-cost medical...
This paper describes the development of a smartphone-based electrochemical biosensor module. The module contains a low power potentiostat that interfaces and harvests power from a smartphone through the phone's audio jack. A prototype with two different potentiostat designs was constructed and used to conduct proof of concept cyclic voltammetry experiments with potassium ferro-/ferricyanide (K4[Fe(CN)...
Multi-channel neural recording devices are widely used for in vivo neuroscience experiments. Incurred by high signal frequency and large channel numbers, the acquisition rate could be on the order of hundred MB/s, which requires compression before wireless transmission. In this paper, we adopt the Compressed Sensing framework with a simple on-chip implementation. To improve the performance while reducing...
We demonstrate a method for identifying and removing electroencephalograph (EEG) artifacts from mobile Brain Computer Interface (BCI) data with few channels. The main components of the method entail; one-time selection of visually inspected “good quality” EEG data from past experiments and outlier detection using statistical methods. The standardly used thresholding and filtering method was compared...
We present a 56-channel neural recording interface with a chopper-stabilized DC-coupled front-end and a programmable mixed-signal DC cancelation feedback. Each recording channel has a fully-differential amplifier with 51–54dB of gain, an input-referred noise of 5µVrms integrated from 10Hz to 5kHz and a CMRR of 65dB. Input DC-coupling allows for a simple chopping scheme without the area overhead of...
Safety features embedded in a 256-channel retinal prosthesis integrated circuit are presented. The biology of the retina and the electrochemistry of the electrode-tissue interface demand careful planning and design of the safety features of an implantable retinal stimulation device. We describe the internal limits and communication safety features of our ASIC, but we focus on monitoring and protection...
Retinal prostheses have successfully proven to be a viable treatment for advanced stages of retinal degenerative diseases such as retinitis pigmetosa. However, current implementations have critical limitations that affect their functionality and resolution. This paper reviews design challenges of the electronics considering the biology of the eye and discusses new approaches for future high-density...
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