Direct and Indirect Measures of Dietary Intake Use of Sensors and Modern Technologies
Dale A. Schoeller, Margriet S. Westerterp-Plantenga in Advances in the Assessment of Dietary Intake, 2017
A sensor in the broadest sense is an object or device that detects events or changes in its environment and provides a corresponding output. The term sensor is often used interchangeably with the term transducer. A transducer is a device that converts one form of energy to another, for example, sound to movement; temperature to electricity. For our purposes, we will consider a transducer to be the component of a more complex sensor or sensing system that allows for an observable response. Sensors may be divided into three types: physical sensors measure distance, mass, temperature, and so on (e.g., Avatar), chemical sensors (chemosensors and chemoreceptors) respond to chemical changes in their environment and biosensors in which a biochemical process is the source of the analytical signal (Hulanicki et al. 1991; Eggin 2004).
Quantitative ultrasound
C M Langton, C F Njeh in The Physical Measurement of Bone, 2016
The term transducer describes a device which interconverts energy forms. The piezoelectric effect describes the interconversion of electrical and mechanical energy. For the generation of ultrasound, an electric signal is applied across a piezoelectric material that induces a mechanical deformation, which in turn produces a pressure wave. Ultrasound piezoelectric transducers for the assessment of bone are generally in the form of a thin circular disc, the thickness of which determines the resonant frequency (F0); the thickness being half a wavelength. For the detection of ultrasound, the piezoelectric material converts a mechanical deformation, due to the ultrasound pressure wave, into an electrical signal that may then be modified and processed. A naturally occurring piezoelectric material is quartz which is still used for some high-frequency (∼50 MHz region) applications. Piezoelectric ceramic materials are generally utilized, the most popular being lead zirconate titanate (PZT), with barium titanate utilized if particularly short (low Q) pulses are required.
Ultrasound Basics
Massimo Zambon in Ultrasound of the Diaphragm and the Respiratory Muscles, 2022
Sound is vibration of a physical medium. In clinical ultrasound, a mechanical vibrator, known as the transducer, is placed in contact with a surface (i.e., the skin, but it can be an internal surface such as the oesophagus) to create tissue vibrations (sound waves). The core of every transducer consists of piezoelectric crystals. Piezoelectricity is the process of using crystals to convert mechanical energy into electrical energy, or vice versa. Therefore, a transducer converts (or transduces) electrical energy to or from mechanical energy. The amplitudes of the returning echoes are represented as pixels of varying brightness along the vertical axis of the display. The brightness correlates with the strength of the returning signal.
Recent approaches to ameliorate selectivity and sensitivity of enzyme based cholesterol biosensors: a review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Anjum Gahlaut, Vinita Hooda, Vikas Dhull, Vikas Hooda
Biosensor is an analytical device which detects the biochemical change produced due to the presence of specific analyte. A signal is produced which is proportional to the concentration of the target analyte present in its proximity. Basic assembly of biosensor consists of recognition layer, transducer and processor. Recognition layer is the main sensing element of the biosensor; it is made up of biological component that can be an enzyme, a cell, antibody, receptor molecule or DNA. Recognition layer is immobilized either directly on transducer or on some other support present in its intimate contact. Transducer acts like a translator that recognizes the physico-chemical change (i.e. pH change, heat transfer, uptake or release of gases or specific ions, electron transfer and mass changes) and converts it into electronic signal and the processor converts it into readable digital output. Schematic representation of biosensor has been depicted in Figure 2. The concept of biosensor was pioneered by Clark for determination of glucose, thereafter concept has been explored widely for determination of various other molecules like cholesterol, lactate, uric acid, hCG, etc. Differentiating on the basis of type of transducer used, biosensors can be categorized into following:
Recent trends and perspectives in enzyme based biosensor development for the screening of triglycerides: a comprehensive review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Vinita Hooda, Anjum Gahlaut, Ashish Gothwal, Vikas Hooda
Technology has helped us to form a biosensor, a device in which an analyte is detected by combination of a biological component with a physico-chemical detector component (Figure 2). Basically, three parts constitute a biosensor – a biological element, detector element or the transducer and allied electronic or signal processors [22]. Enzymes, microorganisms, tissues, organelles, antibodies, cell receptors, nucleic acids can be immobilized as a sensitive biological element for the detection of specific analyte. The transducer represents the second component of the biosensor body and works in a physico-chemical mode like electrochemical, optical, piezoelectrical or thermal that converts the resulting output signal from the interaction of the analyte with the biological element into another quantifiable signal. The continuous or discrete electric signal are generated, which are relative to the amount of single analyte or a group of analytes being sensed [23].
Biosensors for the detection of mycotoxins
Published in Toxin Reviews, 2022
Akansha Shrivastava, Rakesh Kumar Sharma
A biosensor can be defined as any measuring device containing a compound of biological origin and used as a sensing bio-recognition element that is closely associated with a sensor element (physicochemical transducer). Whole microbial cell, antibody, enzyme, protein, and nucleic acid are the most frequently used bio-recognition element. The physicochemical transducer can be electrochemical, optical, piezoelectric optical, and sometimes thermal (Pohanka et al. 2007, Nawaz et al. 2017). A biological recognition element is carefully chosen and immobilized within the biosensor. It must be capable of binding the analyte, which needs to be detected and quantify. During the process, the interaction of target and biorecognition element generates a physicochemical signal eased by the transducer, which is finally interpretable by a read-out device to the user. Fabrication of the biosensor is the most important part of the bio-component. The overall performance of the device depends on factors such as chemical, physical conditions, thickness, and stability of materials used. This process permits sensitive detection of mycotoxins (Evtugyn et al. 2017) (Table 1).
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