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Selection of Sensors, Transducers, and Actuators
Published in Wasim Ahmed Khan, Ghulam Abbas, Khalid Rahman, Ghulam Hussain, Cedric Aimal Edwin, Functional Reverse Engineering of Machine Tools, 2019
Memoon Sajid, Jahan Zeb Gul, Kyung Hyun Choi
A sensor is a device that responds to an external stimulus or an analyte. The stimulus can be anything ranging from a physical entity like touch, pressure, strain, an electromagnetic signal, heat, light, chemical, gas, sound, water, particles, bio-reagents, etc. [1,25–27]. The sensing portion of the device is known as the active region that collects or receives the stimulus and then generates a signal of its own in response [2]. The response of the sensor can be in the form of a passive change in its intrinsic properties like color, electrical resistance, capacitance, and inductance or an active electrical signal in the form of a current or potential difference. We can categorize sensors based on the type of analyte they are detecting like environmental sensors, biosensors, etc., or we can categorize them based on their working mechanism like active sensors and passive sensors. Here, we will follow the later one due to its better versatility and easier understanding, but before that, we will develop understanding about some basic terms associated with sensor characteristics.
Polymeric Hydrogels for Controlled Drug Delivery
Published in Munmaya K. Mishra, Applications of Encapsulation and Controlled Release, 2019
Hira Ijaz, Farooq Azam, Ume Ruqia Tul-Ain, Junaid Qureshi
PEG, also known as poly(oxyethylene)/poly(ethylene oxide), is employed for medical and biomedical applications. Polyethylene glycol dimethacrylate (PEGDMA) and polyethylene glycol methacrylate (PEGMA) are also employed for the preparation of polymeric hybrids ( [Figure 3.6). PEG-based hydrogels are non-toxic, biocompatible, biodegradable, and hydrophilic, which makes them excellent for drug delivery 22]. PEG-based hydrogels are physically, chemically, and biologically stable and stimuli responsive [34]. Due to these novel properties, they are called smart/intelligent gels. Physical stimuli include temperature, pressure, light, solvent, radiation, and electric and magnetic fields. Chemical stimuli include pH, ions, and molecule recognition [32]. Structure of polyethylene glycol (PEG).
Membrane Models
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
A key concept in the modeling of excitable cells is the idea of ion channel selectivity. A particular type of ion channel will only allow certain ionic species to pass through; most types of ion channels are modeled as being permeant to a single ionic species. In most excitable cells at rest, the membrane is most permeable to potassium. is is because only potassium channels (i.e., channels selective to potassium) are open at the resting potential. For a given stimulus to result in action potential the cell has to be brought to threshold, that is, the stimulus has to be larger than some critical size; smaller sub-threshold stimuli will result in an exponential decay to the resting potential. e upstroke, or fast initial depolarization, of the action potential is caused by a large inux of sodium ions as sodium channels open (in some cells, entry of calcium ions through calcium channels is responsible for the upstroke) in response to a stimulus. is is followed by repolarization as potassium ions start owing out of the cell in response to the new potential gradient. While responses of most cells to subthreshold inputs are usually linear and passive, the suprathreshold response-the action potential-is a nonlinear phenomenon. Unlike
Review of the end-of-life solutions in electronics-based smart textiles
Published in The Journal of The Textile Institute, 2021
Van Langenhove and Hertleer (2004) state ‘smart textiles are fabrics or apparel products that contain technologies, which sense and react to the conditions of the environment they are exposed to, thus allowing the wearer to experience increased functionality’. The conditions or stimuli can be electrical, mechanical, thermal, chemical, or a combination of these. The main research in the smart textile field is indefinitely focused on improving the integration level, from moving from garment level to fibre level (Schneegass & Amft, 2017). For example, Katashev et al. (2019) replaced conventional EIT (electrical impedance tomography) electrodes with knitted textiles electrodes where conductive parts are on fibre level. Electronic textiles (e-textiles) are a subcategory of smart textiles that are based on electronics and conductive textiles, e.g. silver-coated fabrics or yarns, conductive inks and/or conductive polymers (Stoppa & Chiolerio, 2014). The e-textiles system includes the traditional electronic components, for example, printed circuit boards (PCB) and non-textile sensors that include ceramics in addition to metals and plastics.
Locomotion control of a biomimetic robotic fish based on closed loop sensory feedback CPG model
Published in Journal of Marine Engineering & Technology, 2021
Deniz Korkmaz, Gonca Ozmen Koca, Guoyuan Li, Cafer Bal, Mustafa Ay, Zuhtu Hakan Akpolat
In the designed sensory feedback Lamprey CPG oscillator, each SN is defined by the following equation: Here, x(SN)i is the membrane potential of SN, τres is the rise time constant of the response generated to the stimulus, τrec is the fall time constant of the response generated to the stimulus, p is the correction coefficient of the stimulus, λ is the stimulus amount and Λ is the threshold value. The threshold value determines when external stimuli has become important and the response has to be produced. When the amount of stimulus is greater than or equal to the threshold value, the SN produces an output. Otherwise, the SN output is zero. In the proposed sensory feedback CPG model, each SN emits excitatory synapses to all MNs. In the experimental studies, τrec = 0.4, τres = 0.1095, p = 2 and Λ = 1 are determined for parameters of the SN. Also, the parameter values of the SNs in the left and right sections are equal to each other.
Wearable electronic textiles
Published in Textile Progress, 2019
David Tyler, Jane Wood, Tasneem Sabir, Chloe McDonnell, Abu Sadat Muhammad Sayem, Nick Whittaker
‘Traditional textiles’, although functional, do not, in most cases, sense, react, or adapt to external stimuli (except for moisture absorption and release by protein and cellulose fibres in reaction to changes in humidity in the immediate environment). The minimum requirement for a smart textile is the ability to sense environmental conditions or an external stimulus, which qualifies it as ‘passive smart'. If the material has the ability to react after sensing, then it qualifies as ‘active smart’ [14]; further categories are explained in Table 1. Stimuli responses can be in the form of mechanical, thermal, electric magnetic and other sources. By responding to change in the environment, the material’s properties change. Key distinguishing qualities of smart textiles are that they are “soft” materials with flexibility and drapeability [14]. How the response to external stimuli changes dependent on the material itself.