Novel probes for pH and dissolved oxygen measurements in cultivations from millilitre to benchtop scale

Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)pH value and the concentration of dissolved oxygen (DO) are key parameters to monitor and control cell growth in cultivation studies. Reliable, robust and accurate methods to measure these parameters in cultivation systems in real time guarantee high product yield and quality. This mini-review summarises the current state of the art of pH and DO sensors that are applied to bioprocesses from millilitre to benchtop scale by means of a short introduction on measuring principles and selected applications. Special emphasis is placed on single-use bioreactors, which have been increasingly employed in bioprocess development and production in recent years. Working principles, applications and the particular requirements of sensors in these cultivation systems are given. In such processes, optical sensors for pH and DO are often preferred to electrochemical probes, as they allow semi-invasive measurements and can be miniaturised to micrometre scale or lower. In addition, selected measuring principles of novel sensing technologies for pH and DO are discussed. These include solid-state sensors and miniaturised devices that are not yet commercially available, but show promising characteristics for possible use in bioprocesses in the near future

Blind Parallel Interrogation of Ultrasonic Neural Dust Motes Based on Canonical Polyadic Decomposition: a Simulation Study

© EURASIP 2017. Neural dust (ND) is a wireless ultrasonic backscatter system for communicating with implanted sensor devices, re-ferred to as ND motes (NDMs). Due to its scalability, ND could allow to chronically record electro-physiological signals in the brain cortex at a micro-scale pitch. The free-floating NDMs are read out by an array of ultrasonic (US) transducers through passive backscattering, by sequentially steering a US beam to the target NDM. In order to perform such beam steering, the NDM positions or the channels between the NDMs and the US transducers have to be estimated, which is a non-trivial task. Furthermore, such a sequential beam steering approach is too slow to sample a dense ND grid with a sufficiently high sampling rate. In this paper, we propose a new ND interrogation scheme which is fast enough to completely sample the entire ND grid, and which does not need any information on the NDM positions or the per-NDM channel characteristics. For each sample time, the US transducers transmit only a few grid-wide US beams to the entire ND grid, in which case the reflected beams will consist of mixtures of multiple NDM signals. We arrange the demodulated backscattered signals in a 3-way tensor, and then use a canonical polyadic decomposition (CPD) to blindly estimate the neural signals from each underlying NDM. Based on a validated simulation model, we demonstrate that this new CPD-based interrogation scheme allows to reconstruct the neural signals from the entire ND grid with a sufficiently high accuracy, even at relatively low SNR regimes.status: publishe

Application of canonical polyadic decomposition for ultrasonic interrogation of neural dust grids: a simulation study

status: publishe

17.5 A 0.8mm3 Ultrasonic Implantable Wireless Neural Recording System with Linear AM Backscattering

Miniaturization of implantable neural recording systems to micron-scale volumes will enable minimally invasive implantation and alleviate cortical scarring, gliosis, and resulting signal degradation. Ultrasound (US) power transmission has been demonstrated to have high efficiency and low tissue attenuation for mm-scale implants at depth in tissue [1, 2, 3], but has not been demonstrated with precision recording circuitry. We present an US implantable wireless neural recording system scaled to 0.8mm3, verified to safely operate at 5cm depth with state of the art neural recording performance an average circuit power dissipation of 13μW, and 28.8μW including power conversion efficiency. Sub-mm scale is achieved through single-link power and communication on a single piezocrystal (Lead Zirconate Titanate, PZT) utilizing linear analog backscattering, small die area, and eliminating all other off-chip components

StimDust: A 6.5mm3, wireless ultrasonic peripheral nerve stimulator with 82% peak chip efficiency

We present a 6.5mm3, 10mg, wireless peripheral nerve stimulator. The stimulator is powered and controlled through ultrasound from an external transducer and utilizes a single 750×750×750μm3 piezocrystal for downlink communication, powering, and readout, reducing implant volume and mass. An IC with 0.06mm2 active circuit area, designed in TSMC 65nm LPCMOS process, converts harvested ultrasound to stimulation charge with a peak efficiency of 82%. A custom wireless protocol that does not require a clock or memory circuits reduces on-chip power to 4μW when not stimulating. The encapsulated stimulator was cuffed to the sciatic nerve of an anesthetized rodent and demonstrated full-scale nerve activation in vivo. We achieve a highly efficient and temporally precise wireless peripheral nerve stimulator that is the smallest and lightest to our knowledge

Beamforming approaches for untethered, ultrasonic neural dust motes for cortical recording : a simulation study

In this paper, we examine the use of beamforming techniques to interrogate a multitude of neural implants in a distributed, ultrasound-based intra-cortical recording platform known as Neural Dust. We propose a general framework to analyze system design tradeoffs in the ultrasonic beamformer that extracts neural signals from modulated ultrasound waves that are backscattered by free-floating neural dust (ND) motes. Simulations indicate that high-resolution linearly-constrained minimum variance beamforming sufficiently suppresses interference from unselected ND motes and can be incorporated into the ND-based cortical recording system.status: publishe

A Minimally Invasive 64-Channel Wireless μeCoG Implant

Emerging applications in brain-machine interface systems require high-resolution, chronic multisite cortical recordings, which cannot be obtained with existing technologies due to high power consumption, high invasiveness, or inability to transmit data wirelessly. In this paper, we describe a microsystem based on electrocorticography (ECoG) that overcomes these difficulties, enabling chronic recording and wireless transmission of neural signals from the surface of the cerebral cortex. The device is comprised of a highly flexible, high-density, polymer-based 64-channel electrode array and a flexible antenna, bonded to 2.4 mm × 2.4 mm CMOS integrated circuit (IC) that performs 64-channel acquisition, wireless power and data transmission. The IC digitizes the signal from each electrode at 1 kS/s with 1.2 μV input referred noise, and transmits the serialized data using a 1 Mb/s backscattering modulator. A dual-mode power-receiving rectifier reduces data-dependent supply ripple, enabling the integration of small decoupling capacitors on chip and eliminating the need for external components. Design techniques in the wireless and baseband circuits result in over 16× reduction in die area with a simultaneous 3× improvement in power efficiency over the state of the art. The IC consumes 225 μW and can be powered by an external reader transmitting 12 mW at 300 MHz, which is over 3× lower than IEEE and FCC regulations