Development and use of electronic devices from day to day life activities of human to its industrial & business applications have already revolutionized our world. Besides, electronic devices/sensors are being developed to work at par with the functions of human sense organs. Human has in general five sense qualities like touch, taste, smell, hear, vision and the whole actions of human body are controlled on the basis of electric signals through their respective body parts as: skin, tongue, nose, ear and eye. Electronic development has progressed well to replicate these sense functions with electronic devices/sensors called: e-skin, e-tongue, e-nose, hearing aids and electronic-eye. Electronics not limiting to five senses has moved further to sixth and seventh senses also in terms of wearable interaction and gesture control of electronic devices. And finally, moving further into the digital world, we will be able to induce not just familiar but completely new, never before known senses. For example, a banking chip implanted under the skin may, one day, create the sense of a full or empty bank account. Connecting to the social network, we will have to experience “physically” the distance to those speaking, or the actuality, the time-freshness, of what will be said. The first bunch of digital senses will simulate natural ones, just because we have to rest on something familiar in our cognitive experience. Then, we will develop derivative senses; these derivations will have been detaching farther and farther from what we have been familiar with in our previous physical experience. Once in the future, we will have moved far enough to become completely resettled in the digital environment that will turn out to be the natural environment for the new, digital post-human being. By that moment, we will be able to design completely new sensations, with whatever range of excitement.
Basics of electronic sense
In electronics, sense is a technique used in power supplies to produce the correct voltage for a load. Although simple batteries naturally maintain a steady voltage (except in cases of large internal impedance), a power supply must use a feedback system to make adjustments based on the difference between its intended output and its actual output. If this system is working, the latter will be very close to the former. Two types of sense are used, depending on where the power supply output is measured. In local sense, the supply simply measures the voltage at its output terminals, where the leads to the load connect. This method has the problem of not accounting for the voltage drop due to resistance of the leads, which is proportional to the amount of current drawn by the load. That is, the supply might be producing the correct voltage at its output terminals, but there will be a lower voltage at the input terminals of the load. When this might cause a problem, remote sense can be used to force the power supply to counteract the voltage drop by raising the voltage at its output terminals. If successful, it will exactly cancel the drop along the leads, yielding the correct voltage at the input terminals of the load. This is accomplished by using separate “sense leads,” connected to the load’s input terminals, to measure the output voltage. (Because the sensing function draws only a very small amount of current, there is practically no additional voltage drop due to the sense leads themselves). Many power supplies that are equipped with remote sense can cause catastrophic damage to the loads if they turned on while the sense leads are unconnected. To avoid this, some supplies are equipped with auto sense, which will automatically switch between local and remote sensing depending on whether the sense leads are correctly connected.
Development in electronic senses
E-Noses and E-Tongues, as their names suggest, are inspired by the neurophysiology of smell and taste and attempt to mimic the abilities of their human counterparts. These technologies automate the evaluation of samples with complex composition and are able to recognize specific properties and characteristics. In animals, sensory information is processed by the neural system. Likewise, data collected through selective sensor arrays must be analyzed by pattern recognition tools that employ various mathematical and statistical processing techniques. Such systems can provide quantitative results and, in some cases, are even able to detect differences that a human sensory panel cannot distinguish. In food analysis, arrays of gas sensors are termed “E-Noses” while arrays of liquid sensors are referred to as “E-Tongues”. The first scientific literature on these systems appeared in the 1980s but it has only been in the last decade, due to the food industry’s progressive interest in rapid at- and on-line analysis of product quality and safety, that special attention has been given to emerging technologies in electronic senses.
E-Nose instruments typically exploit four main sensor types: conducting polymers (CP), metal oxide semiconducting (MOS), metal oxide semiconducting field-effect transistors (MOSFET), and oscillating sensors, such as quartz crystal microbalances (QCM). E-Tongue instruments generally use the following analytical solutions: mass sensors, which are miniaturized solid-state devices that exploit the piezoelectric effect; potentiometric methods, for example, ion-selective electrodes; and voltammetric or optical sensors, in which an indicator molecule changes its optical properties when exposed to a target analyte. Hybrid E-Tongues, based on a combination of potentiometry, voltammetry and conductimetry, offer great potential.
Concrete applications of the discriminating power exhibited by E-Noses can be found in the analysis of meat flavors, volatile organic compounds (VOCs) formed during post-harvest ripening of fruits, ham product evolution during storage, packaging off-flavors, olive oil defects and the identification of geographical origin of foodstuffs. In the last 10 years, for example, Barilla has been successfully implementing MOS-based E-Noses in different quality control labs to recognize residual solvents and to continuously monitor the various plastic food-packaging materials adopted within bakery production sites. At Barilla, E-Noses are, in fact, used as the first appraiser of packaging quality, which limits the number of gas chromatographic confirmatory analyses required solely to the samples that are marked as uncertain or bad by the MOS instrument. E-Tongues can be used to monitor and discriminate among mineral water, coffee and soft drink samples. Reported applications of E-Tongues in food analysis cover process monitoring, foodstuff recognition/characterization, evaluation of ‘freshness’, quality control and authenticity assessments.
Applications of electronic senses
- Electronic senses offer advantages such as not having to use humans for what may sometimes be unpleasant or even dangerous tasks, as well as consistency. In the very short-term future, sight, taste and smell sensors will be available to new industries to incorporate into their own products, or for individuals directly.
- Up to now, electronic senses have had straight industrial applications. The food, beverage, pharmaceuticals, plastics, packaging and environmental industries have clear uses for electronic senses. They can detect when flavors or odors in food are “off,” and if there has been contamination or migration of compounds from plastic packaging into content. MOS odor sensors also can control how fast a flavor is diluted, ensure quality-control, or reverse-engineer an aroma. Its electronic tongues can assess things like bitterness, whether a taste remains stable over time, or whether a product has been adulterated.
- The refrigerator of the future may have sensors that detect when food is going bad. It might be connected to a food-management system that alerts a resident, who can then check in order to make a grocery list.
- Cars in the future may have sensors that detect carbon dioxide. The level of carbon dioxide rises in a car with, say, a family driving on a long trip with the windows shut. That’s dangerous, because carbon dioxide can make the driver sleepy. A sensor would alert the driver and passengers that they need to stop for fresh air.
- Doctors in the future may give patients a breath test to detect the onset of diseases like diabetes or cancer. A new study shows that organic compounds in exhaled breath can indicate whether a person has lung cancer—as well as its stage—and can distinguish cancer from chronic obstructive pulmonary disease.
- Electronic senses were applied in order to evaluate the effect of brewing temperature on the sensorial properties of espresso coffees (ECs) produced by a bar machine of the latest generation able to work with constant, increasing and decreasing water temperature profiles. The obtained ECs were analyzed by e-nose, e-tongue and e-eye to depict their aroma and taste fingerprint and to evaluate the visual characteristics of foam. Physicochemical analyses were carried out to determine the extraction rate of typical EC components and to evaluate their antioxidant activity. The electronic devices coupled with multivariate statistical analysis demonstrated a good ability to discriminate and characterize coffee samples on the basis of their sensorial properties in relation to the brewing temperature. According to these results, electronic senses can be applied to assess the influence of the percolation parameters on the sensory attributes of ECs, thus resulting useful tools for the optimization of processing conditions.
- Sensory characteristics of food products gain increasing importance in international food research and industry to meet consumer needs. Food producer make efforts to improve the quality and to offer a wide range of foods of excellent quality. Comparison with existing brands in the sensory point of view on the market and developing products parallel with consumer needs are essential for the successful new product launch. Usually trained sensory panel is used to evaluate product quality. However, the reliability of the sensory results is highly dependent on panelists’ acuity and the correct application of the sensory practice. Therefore, the measurement of sensory attributes by instrumental methods is a desirable aim. A new concept has been introduced in the sensor development using several sensors of low selectivity simultaneously.
- Scientists have presented a detector that can distinguish smells better than a service dog. It’s a sensor for detecting explosive vapors and identifying them, calling it an electronic nose. The device is able to sense and recognize traces of almost all types of explosives, from saltpetre to hexogen. Hexogen cannot be detected even by even the most advanced technology.
- Skin is probably one of the best wearable technologies that nature ever developed. Skin on our fingertips contains pressure sensors that produce voltage pulses when we touch things. The frequency at which these pulses are created gives the brain information about what we’re touching. New electronic skin could help give prosthetic limbs a human sense of touch. Prosthetic limbs could soon be covered in an electronic skin that mimics human touch. Scientists report on the development of a flexible plastic skin that can communicate a sense of pressure to brain cells. The plastic skin generates voltage pulses when pressure is applied. The higher the pressure, the closer the carbon nanotubes are pushed together. This increases the conductivity frequency of the voltage pulses. The electronic skin is capable of generating the same frequency of voltage pulses as human skin – up to 200 hertz. Being digital also means the system is low powered, which is also important since, to mimic human touch, prosthetic skin will need to have thousands of sensors in the space of a fingertip to feel properly. At the moment the electronic skin can only detect static pressure rather than moving pressure, for example a brushing action. Further developments hoped for a range of different sensors within five years that can give artificial skin the full range of features involved in touch, including vibration, texture and temperature.
- An electrochemical nose, also called an e-nose, is an artificial olfaction device with an array of chemical gas sensors, a sampling system, and a pattern-classification algorithm to recognize, identify, and compare gases, vapors, or odors. In this way the e-nose mimics the human olfactory system. These devices have been successfully used in a wide variety of applications including detection of food quality, wastewater management, measurement, and detection of air and water pollution, in health care, and in warfare. One of their strengths is that the data gathered can be interpreted without bias. The use of nanomaterials in e-nose applications is gaining ground, as has the capability of creating sensors with ultrahigh sensitivities and fast response (due in part to a smaller structure). The smaller sensor size also promotes integration into a larger number of devices. An attractive class of materials for functional nanodevices is metal-oxide semiconductors. They offer simple operation and ease of fabrication and the potential for compatibility with microelectronic processing, as well as low cost and low-power consumption.
- The electronic tongue (e-tongue) uses an array of liquid sensors that mimic the human sense of taste, without the intrusion of other senses such as human vision and olfaction that often interfere with our taste perception. Within a few years, researchers anticipate that a machine that experiences flavor will determine the precise chemical structure of food and why people like it. Digital “taste buds” also will help us to eat smarter and healthier. The e-tongue measures and compares tastes using sensors to receive information from target chemicals and then sends it to a pattern-recognition system. The result is the detection of taste based on the human palate. E-tongues often are used in liquid environments to classify the contents of the liquid, identify the liquid itself, or sometimes to discriminate between samples. Most e-tongues are based either on potentiometric or amperometric sensors. The taste sensors have artificial polyvinyl chloride (PVC)/lipid membranes that interact with a target solution such as caffeinated beverages. The membrane potential of the lipid membrane changes – which is the sensor output or measurement. Investigating potential change results in measuring the “taste” provided by the output of the chemical substances. With the array, multiple sensors provide this output and form a unique fingerprint.
- Hearing systems are increasingly being trained by “listening” to sounds, detecting patterns and building models to decompose sounds. One of the most common applications for sensors in this segment is in hearing aids. Digital advances have made today’s hearing aids smaller, smarter and, fortunately, easier to use. The most advanced hearing aids are now interacting with other devices, such as smartphones and digital music players, to deliver sounds directly and wirelessly to the listener. Recent improvements are based on better microprocessors and noise-reduction software so that the hearing aid can be selective about the types of sound it amplifies, muffles, or suppresses. Much of the focus of current research is on directionality and speech enhancement. Sound systems can employ digital-signal processing to automatically shift between two different types of microphones in order to pick up either a single speaker’s voice or sound coming from all around. Digital-speech enhancement can now increase the intensity and audibility of some segments of human speech. Research projects are underway to reduce the size and cost of hearing aids, improve their directional capabilities, and identify and amplify desired sounds such as a human voice while muting background noise.
- Electronic-skin prototypes are stretchy, thin films that can sense temperature, pressure and even monitor blood oxygen or alcohol levels. But most of these devices are missing a key feature of real skin that allows us to feel a wider range of conditions: hair. Now researchers have combined hair-like wires with electronic skin to make a more versatile sensor for robots, prosthetics and other applications. Robots and prosthetics are becoming ever more human-like, but the electronic skins designed to enhance their usefulness don’t yet have the full range of tactile senses that we have. To capture that sensation, some researchers have developed separate sensors that mimic this fine hair by sensing and detecting air flow. However, that’s about all these particular devices can do.
- The technique of electronic tongues or taste sensors has developed very fast during the last years due to its large potential, and the interest for the concept is steadily increasing. In principle, they function in the same way as the electronic nose, but are used in the aqueous phase.
Future of electronic senses
It is realistic to imagine that within the next few years, thanks to significant advances in micro-fluidics and electronics, that E-Nose and E-Tongue technology will evolve both in terms of robustness and reduction in the current need to optimize each application – a process that requires significant investment of time and resources. Miniaturization will further extend flexibility. Beyond food, E-Sense technology may find applications in other industries, for instance in environmental analysis to detect water contamination or illicit drugs; in clinical diagnostics to monitor saliva, sweat or urine; and in agriculture to detect fungal contamination in feed. There is great potential in these applications, in spite of the fact that the term ‘E-Tongue’ doesn’t conjure up a wonderful image in some instances. Challenges that remain with both E-Nose and E-Tongue technologies are the needs to improve sampling procedures (by reducing clean-up or extraction before analysis, for example) and to reduce carry-over/environmental noise (for instance, in the form of moisture contamination), which affect sensor drift and sensitivity.
- For visually impaired people, devices are developedthat can transmit the spectrum of colours and lighting around, along with spatial orientation intoa mouth cavity, using, again, slight electric stimulation.
- A special electric dog collar can charge an animal with electric shock when it starts barking too much or runs too far away. So, this device brings up a dog with a sense of attachment. This dog collar may start with a vibration to warn a dog before punishment, so the device provides a dog not just with a “new” sensation, but also with a presentiment.
- Scientists have been developing a new device,the feel-space belt, which allows a wearer to feel the Earth’s magnetic field and be oriented in the four winds, just like birds and bats are. The feel-space belt just transforms the magnetic currents into vibrations that the body can easily perceive. In reality, the new sensation is just a cognitive effect induced by a physical impact on receptors of the old sense, which is tactility. It is safe to say that this transition of meaning of one “sense” via the other sense is symbolical. It requires an intermediary; therefore, it requires time and effort to recognize and learn the “content” of the signals, while the real, natural senses are immediate for perception, as they require no symbolic interpretation. We feel cold or water directly, by sensors designed to feel such things.
- Sensory punishing devices are already developed for people e.g., punishes the wearer with a slight electric shock in case the wearer passes a deadline, or smokes when having pledged to quit, or breaks some other rules established by themselves. The device is designed to facilitate the fight against bad habits.
Conclusion
Considering the endless future potential for the design and control of digitally induced senses, we have to admit that this high will be unlimited. The ability to control senses unleashes an uncontrolled sense of excitement, to which, as of now, we can find nothing to compare. Moving further into the digital world, we will be able to induce not just familiar but completely new, never before known senses. For example, a banking chip implanted under the skin may, one day, create the sense of a full or empty bank account. Connecting to the social network, we will have to experience “physically” the distance to those speaking, or the actuality, the time-freshness, of what will be said. We will have to sensorily perceive the massiveness, or virality of a topic.
Author
Dr. S. S. Verma, Department of Physics, S.L.I.E.T.
