http://cau.ac.kr/~jjang14/BioMEMS/Lazcka_BSBE_Pathogen_Detection_Review_2006.pdf

Pathogen detection: a perspective of traditional methods and biosensors.

Sensory substitution systems provide their users with environmental information through a human sensory channel (eye, ear, or skin) different from that normally used or with the information processed in some useful way. The authors review the methods used to present visual, auditory, and modified tactile information to the skin and discuss present and potential future applications of sensory substitution, including tactile vision substitution (TVS), tactile auditory substitution, and remote tactile sensing or feedback (teletouch). The relevant sensory physiology of the skin, including the mechanisms of normal touch and the mechanisms and sensations associated with electrical stimulation of the skin using surface electrodes (electrotactile, or electrocutaneous, stimulation), is reviewed. The information-processing ability of the tactile sense and its relevance to sensory substitution is briefly summarized. The limitations of current tactile display technologies are discussed, and areas requiring further research for sensory substitution systems to become more practical are suggested. >

/pdf/electrotactile-and-vibrotactile-displays-for-sensory-1w0op8f85n.pdf

Electrotactile and vibrotactile displays for sensory substitution systems

Fractional (non-integer order) calculus can provide a concise model for the description of the dynamic events that occur in biological tissues. Such a description is important for gaining an understanding of the underlying multiscale processes that occur when, for example, tissues are electrically stimulated or mechanically stressed. The mathematics of fractional calculus has been applied successfully in physics, chemistry, and materials science to describe dielectrics, electrodes and viscoelastic materials over extended ranges of time and frequency. In heat and mass transfer, for example, the half-order fractional integral is the natural mathematical connection between thermal or material gradients and the diffusion of heat or ions. Since the material properties of tissue arise from the nanoscale and microscale architecture of subcellular, cellular, and extracellular networks, the challenge for the bioengineer is to develop new dynamic models that predict macroscale behavior from microscale observations and measurements. In this paper we describe three areas of bioengineering research (bioelectrodes, biomechanics, bioimaging) where fractional calculus is being applied to build these new mathematical models.

Fractional calculus models of complex dynamics in biological tissues

Wearable sensors have recently seen a large increase in both research and commercialization. However, success in wearable sensors has been a mix of both progress and setbacks. Most of commercial progress has been in smart adaptation of existing mechanical, electrical and optical methods of measuring the body. This adaptation has involved innovations in how to miniaturize sensing technologies, how to make them conformal and flexible, and in the development of companion software that increases the value of the measured data. However, chemical sensing modalities have experienced greater challenges in commercial adoption, especially for non-invasive chemical sensors. There have also been significant challenges in making significant fundamental improvements to existing mechanical, electrical, and optical sensing modalities, especially in improving their specificity of detection. Many of these challenges can be understood by appreciating the body's surface (skin) as more of an information barrier than as an information source. With a deeper understanding of the fundamental challenges faced for wearable sensors and of the state-of-the-art for wearable sensor technology, the roadmap becomes clearer for creating the next generation of innovations and breakthroughs.

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Wearable sensors: modalities, challenges, and prospects

The invention relates to methods and devices for remote or distributed continuous monitoring of physiologically relevant states. The invention provides for methods to automatically detect deviations or other states in physiological parameters and automatically alert a measured subject, user or other authorized party. The device provides for a universal platform for sensors, and further provides for the automatic compensation or distribution of devices or bioactive agents at appropriate levels and/or intervals in response to deviations or other states sensed in various physiological parameters.

Gateway platform for biological monitoring and delivery of therapeutic compounds

Bioelectricity (or bioelectromagnetism) relates to the study of biological electrical currents, and bioimpedance deals with the measurement of electrical conductivity. They are intimately linked to biomedical engineering, with major significance for development of novel medical devices, as well as the study of biological rhythms. This completely updated new edition remains the most comprehensive reference tool for this intricate, interdisciplinary field. The authors, both internationally recognized experts in the field, have thoroughly revised the entire text. It remains the only such work that discusses in detail dielectric and electrochemical aspects, as well as electrical engineering concepts of network theory. The highly effective, easy to follow organization has been retained, with new discussion of state-of-the-art advances in finite element analysis, endogenic sources, control theory, tissue electrical properties, and invasive measurements.There are two all new chapters on bioelectricity, along with an introduction to Geselowitz theory, the Maxwell basis of bioimpedance, and multivariate analysis as an alternative. This title features: increased emphasis on bioelectricity and potential clinical applications; two all new chapters dealing with electrical properties of passive and excitable tissue; and, expanded discussion of finite element modelling and a broad range of applications. It provides a complete 'all in one' reference source for a multidisciplinary, complex field. It includes many additional figures and all improved, newly drawn illustrations throughout.

Bioimpedance and Bioelectricity Basics

Tetrapolar electrode systems are commonly used for impedance measurements on biomaterials and other ionic conductors. They are generally believed to be immune to the influence from electrode polarization impedance and little can be found in the literature about possible pitfalls or sources of error when using tetrapolar electrode systems. In this paper we show that electrode polarization impedance can indeed influence the measurements and that also other phenomena such as negative sensitivity regions, separate current paths and common-mode signals may seriously spoil the measured data.

/pdf/sources-of-error-in-tetrapolar-impedance-measurements-on-jc7b3hmpb5.pdf

Sources of error in tetrapolar impedance measurements on biomaterials and other ionic conductors

The dielectric properties of biological cells and tissues are very remarkable. They typically display extremely high dielectric constants at low frequencies, falling off in more or less distinct steps as the excitation frequency is increased. Their frequency dependence permits identification and investigation of a number of completely different underlying mechanisms, and hence, dielectric studies of biomaterials have long been important in electrophysiology and biophysics. As an example, Hober (1, 2) deduced from dielectric studies that erythrocytes are composed of a poorly conducting envelope enclosing a conducting electrolyte, and in 1925, Fricke (3) derived a value of 3.3 nm for the thickness of this envelope. Hence their bioimpedance research provided early indication of the ultrathin cell membrane. As we shall see later, interfaces play a significant role in the frequency dependence of complex materials, particularly at audio and subaudio frequencies.

/pdf/interface-phenomena-and-dielectric-properties-of-biological-4z2x6zus1j.pdf

Interface phenomena and dielectric properties of biological tissue

The methods for the individual determination of skin surface electrode impedances are briefly discussed. A measurement technique is described with which it is possible to measure two skin surface electrodes simultaneously, but individually, at the same frequency. The design of a small, portable, battery-operated meter using this principle is described with block diagrams. Results are presented from the study of bilateral g.s.r. waves, the site dependence of the skin impedance, the differences between 10Hz and 1000 Hz data, and tissue segment impedance.

Impedance measurement of individual skin surface electrodes.

In this paper, we characterize the polarization impedance behavior of several common metals in diluted NaCl solution operated at low current densities. The objective was to provide a useful reference for those wishing to calculate the electrode polarization impedance in diluted NaCl solutions. Serial equivalent resistance (R) and capacitance (C) for silver, aluminum, gold, platinum, and medical stainless-steel were measured as a function of frequency (10/sup -2/-10/sup 3/ Hz) and NaCl concentration (2.4-77.0 mmol/L). The ratio of electrode polarization impedance with respect to the bulk resistance was calculated and plotted against concentration for each metal. Such a ratio shows the effect of the electrode polarization contribution as a function of electrolyte concentration when the bulk resistance of the solution changes. All metals showed a decrease of serial resistance R/sub p/ and capacitance C/sub p/ as a function of frequency. The medical stainless-steel electrode showed largest impedance values at lower frequencies compared to the other electrodes, and was concentration independent at all frequencies. Aluminum had smallest polarization impedance at low frequencies. Pure gold and platinum behaved similar with the exception that the serial resistance for gold showed a lower value at higher frequencies.

/pdf/electrode-polarization-impedance-in-weak-nacl-aqueous-2dljlvqf66.pdf

Sverre Grimnes

Papers

Bioimpedance and Bioelectricity Basics

Sources of error in tetrapolar impedance measurements on biomaterials and other ionic conductors

Interface phenomena and dielectric properties of biological tissue

Impedance measurement of individual skin surface electrodes.

Electrode polarization impedance in weak NaCl aqueous solutions