This editorial accompanies the launch of BMC Biomedical Engineering, a new open access, peer-reviewed journal within the BMC series, which seeks to publish articles on all aspects of biomedical engineering. As one of the first engineering journals within the BMC series portfolio, it will support and complement existing biomedical communities, but at the same time, it will provide an open access home for engineering research. By publishing original research, methodology, database, software and review articles, BMC Biomedical Engineering will disseminate quality research, with a focus on studies that further the understanding of human disease and that contribute towards the improvement of human health.

Cytomimetic circuits represent a novel, ultra low-power, continuous-time, continuous-value class of circuits, capable of mapping on silicon cellular and molecular dynamics modelled by means of nonlinear ordinary differential equations (ODEs). Such monolithic circuits are in principle able to emulate on chip, single or multiple cell operations in a highly parallel fashion. Cytomimetic topologies can be synthesized by adopting the Nonlinear Bernoulli Cell Formalism (NBCF), a mathematical framework that exploits the striking similarities between the equations describing weakly-inverted Metal-Oxide Semiconductor (MOS) devices and coupled nonlinear ODEs, typically appearing in models of naturally encountered biochemical systems. The NBCF maps biological state variables onto strictly positive subthreshold MOS circuit currents. This paper presents the synthesis, the simulation and proof-of-concept chip results corresponding to the emulation of a complex cellular network mechanism, the skeleton model for the network of Cyclin-dependent Kinases (CdKs) driving the mammalian cell cycle. This five variable nonlinear biological model, when appropriate model parameter values are assigned, can exhibit multiple oscillatory behaviors, varying from simple periodic oscillations, to complex oscillations such as quasi-periodicity and chaos. The validity of our approach is verified by simulated results with realistic process parameters from the commercially available AMS 0.35 μm technology and by chip measurements. The fabricated chip occupies an area of 2.27 mm2 and consumes a power of 1.26 μW from a power supply of 3 V. The presented cytomimetic topology follows closely the behavior of its biological counterpart, exhibiting similar time-dependent solutions of the Cdk complexes, the transcription factors and the proteins.

This paper introduces and applies practical area-reduction techniques on the analogue, externally linear-internally nonlinear (ELIN), complementary metal-oxide semiconductor (CMOS) implementation of a cochlear channel. This channel is constructed on the basis of the biomimetic auditory filter called One-Zero Gammatone Filter (OZGF) and it has been synthesised using ultra-low power, Class-AB, biquadratic filters, which employ MOS transistors that operate in their weak inversion regime. The realisation of linear capacitors with appropriately configured MOS transistors, the order reduction of the OZGF transfer function and the employment of hyperbolic sine companding filters can lead to area reductions that range from 61.8%, up to 91.9% of the original size. Comparative simulation results highlight the trade-offs between performance, linearity, noise and power consumption of the designs.

This paper aims to provide qualitative and quantitative answers to questions related to the impact of transistor-level design parameters upon the performance and accuracy of static and dynamic translinear (TL) circuits in subthreshold CMOS. A methodical, step-by-step, symbolic analysis, exploiting a simplified EKV-based approximation is performed upon customary static TL topologies, including the four MOS transistor (MOST) multiplier/divider, the squarer circuit and the alternating formation of a six MOST multiplier/divider. The logarithmic integrator is treated as a typical dynamic TL analysis example. The produced EKV-based symbolic analysis results are compared against the ideally expected behaviours and Spectre®-BSIM3V3model-simulations. The satisfying agreement between the proposed EKV-based model and Spectre simulator allowed us to proceed further and investigate the conditions under which optimal behaviour is achieved. Optimisation techniques, based on MOSTs' geometrical parameters combinations, resulted in the articulation of practical design rules

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