Electronic Senses to Touch Us All

Dr S.S. Verma is a professor at Department of Physics, Sant Longowal Institute of Engineering and Technology, Sangrur, Punjab

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Electronic skin is capable of generating the same frequency of voltage pulses as human skin—up to 200 hertz. Being digital 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.

Currently electronic skin can only detect static pressure rather than moving pressure (for example, a brushing action). It is hoped that further development of a range of different sensors within five years will give artificial skin the full range of features involved in touch, including vibration, texture and temperature.

For visually impaired people, devices have been developed that can transmit the spectrum of colours and lighting around, along with spatial orientation into a mouth cavity, using slight electric stimulation.

A special electric collar can charge dogs with electric shock when these start barking too much or run too far away. So, it brings up the dogs with a sense of attachment. The dog collar may start with a vibration to warn before punishment.

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Sensory punishing devices have already been developed for people. These punish the wearer with a slight electric shock in case the wearer passes a deadline, smokes after having pledged to quit or breaks some other rules established by themselves. The device is designed to facilitate the fight against bad habits.

Scientists are developing a feel-space belt that allows the wearer to feel the Earth’s magnetic field and be oriented in the four winds, just like birds and bats. The 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 recognise and learn the content of signals, while the real, natural senses are immediate for perception as these require no symbolic interpretation. We feel cold or water directly by sensors designed to feel such things.

Technological advancements

As mentioned earlier, e-nose is an artificial olfaction device with an array of chemical gas sensors, a sampling system and a pattern-classification algorithm to recognise, identify and compare gases, vapours or odours. Thus e-noses mimic the human olfactory system.

Apart from food quality detection, these devices have been successfully used in a wide variety of applications including wastewater management, measurement and detection of air and water pollution, healthcare and warfare. One of their strengths is that the data gathered can be interpreted without bias.

Use of nanomaterials in e-nose applications is gaining ground, and so is the capability to create sensors with ultra-high sensitivities and fast response (partly due to a smaller structure). Smaller sensor size allows integration into a larger number of devices. An attractive class of materials for functional nanodevices is metal-oxide semiconductors. These offer the advantages of simple operation, ease of fabrication and compatibility with microelectronic processing, as well as low cost and low power consumption.

As regards e-tongue, within a few years, researchers anticipate a machine that determines the precise chemical structure of food and why people like it. Digital taste buds will also help us to eat smarter and healthier.

E-tongues are used in liquid environments to classify contents of the liquid, identify the liquid itself or discriminate between samples. Most e-tongues are based either on potentiometric or amperometric sensors. Taste sensors have artificial polyvinyl chloride (PVC)/lipid membranes that interact with a target solution such as caffeinated beverages. Change in the potential of the lipid membrane is the sensor output or measurement. Investigating potential change results in measuring the taste provided by the output of the chemical substances. Multiple sensors of the sensor array provide this output to 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 hearing aids. Digital advances have made today’s hearing aids smaller, smarter and easier to use. The most advanced hearing aids can interact 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 current research is focused 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.

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