Towards ultra-low power bio-inspired processing

The natural world is analogue and yet the modern microelectronic world with which we interact represents real world data using discrete quantities manipulated by logic. In the human space, we are entering a new wave of body-worn biosensor technology for medical diagnostics and therapy. This new trend is beginning to see the processing interface move back to using continuous quantities, which are more or less in line with the biological processes. We label this computational paradigm “bio-inspired” because of the ability of silicon chip technology which enables the use of inherent device physics, allowing us to approach the computational efficiencies of biology. From a conceptual viewpoint, this has led to a number of more specific morphologies including neuromorphic and retinomorphic processing. These have led scientists to model biological systems such as the cochlea and retina and gain not only superior computational resource efficiency (to conventional hearing aid or camera technology), but also an increased understanding of biological and neurological processes

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (a parts per thousand 100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (a parts per thousand 60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 +/- 0.09 mu M) followed by MWCNT-SPCE (0.48 +/- 0.07 mu M) and SPCE (0.98 +/- 0.2 mu M). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 +/- 3.6 nM, dopamine of 640.2 +/- 9.2 nM, octopamine of 3341 +/- 15 nM, pyrogallol of 50.10 +/- 2.9 nM and 3,4-dihydroxy-l-phenylalanine of 980.7 +/- 8.7 nM using 50 mu M H2O2 in the flow carrier