Touch

Our sense of touch opens our minds to a wealth of sensations about our world; vibrations tell us a train going by, we can feel objects move in our hands or know when they are resting against us, we experiences stickiness of a surface as we pull away and feel our skin stretch, the wind blowing our hair, or an insect tickling the short hairs as it crawls along the arm, and the warmth of a rock that’s been laying in the sun. Our since of touch is so precise that we can perceive a bump of 1/25thousanth of an inch with our finger tips.
These sensations are felt through the dermis – the second layer of skin – which is filled with millions of tiny nerve endings. But before we look at the process, let’s look at some facts about the sensor organ:

Facts about the skin

  • The skin is the largest organ of the body accounting for about 15% of body weight.
  • The average adult’s skin covers an area of 2 square meters (approximately 21 square feet of skin, which weighs 9 lbs).
  • Skin contains more than 11 miles of blood vessels.
  • The eyelids have the thinnest skin – about 0.02 mm thick
  • The feet have the thickest skin – about 1.4 mm thick
  • The skin renews itself every 28 days which accounts for about 50% of the dust in the average home
  • The skin is its own microbiome which host approximately 1000 species and one billion individual bacteria

The Process
The dermis is filled with millions of tiny nerve endings (receptors) that provide information about tactile contact. The two main types of receptors are Thermoreceptors which detect cold and heat, and Mechanoreceptors which detect pushing, pulling, body movement, and other physical sensations such as vibrations.

When a stimulus is experienced, the nerve endings convey information to a part of the brain called the “sensory homunculus” which corresponds to the touch receptors of the body. Interestingly, the more receptors there are in parts of the body, the more the brain perceive those parts, so the brain actually perceives areas like the hands, lips, feet, and eyes as enormous (but remember, the brain is also very good at making us perceive such experiences as normal).

Dermis.png

Observation
Touch is an illusion. We can never really touch anything. The electrons in the atoms of our skin cells repel electrons in the objects we “touch” preventing us from actually meeting anything molecule to molecule.

Web Applications
With the arrival of the mouse and later touch screens the sense of touch took its first steps as interface tool for computers. Researchers are currently working on a variety of interfaces based on touch that will change the way we use computers. Katherine Kuchenbecker TED Talk on the Technology of touch is a very good introduction to such interfaces – tools that can help you virtually feel surfaces using forces and vibration sensors, motion tracking, and accelerometers. Research in touch technology may lead to remote surgery with touch sensing gloves, or teaching tools for arts like sculpting or sports.

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