Tweezers

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Tweezers are tools used for picking up small objects that are not easily handled with the human hands. They are probably derived from tongs, pincers, or scissors-like pliers used to grab or hold hot objects from the dawn of recorded history.

Tweezers make use of two third-class levers connected at one fixed end (the fulcrum point of each lever), with the pincers at the others.

Tweezers have many uses, such as gold panning, in the manual construction or repair of many things such as models, clockwork, surface mount electronics; or in cosmetics for plucking eyebrows.

[edit] History

Two sticks would be used to pinch another stick over a stone age fire. Tweezers are known to have been used in predynastic Egypt. There are drawings of Egyptian craftsmen holding hot pots over ovens with a double-bow shaped tool. Asiatic tweezers, consisting of two strips of metal brazed together were common to Mesopotamia and India about 3000 B.C. These likely served purposes such as catching lice.^[1] There is evidence of Roman shipbuilders pulling nails out of construction with plier-type pincers.

[edit] Types

Tweezers come in a variety of tip shapes, including pointed, blunt and tapered. There are also various types of specialised forms of tweezers, including:

• Optical tweezers use light to really manipulate microscopic objects as small as a single atom. The radiation pressure from a focused laser beam is able to trap small particles. In the biological sciences, these instruments have been used to apply forces in the pico Newton range and to measure displacements in the nm range of objects ranging in size from 10 nm to over 100 mm.

• Magnetic tweezers use magnetic forces to manipulate single molecules (such as DNA) via paramagnetic interactions. In practice it is an array of magnetic traps designed for manipulating individual biomolecules and measuring the ultrasmall forces that affect their behavior.

• Electric tweezers deliver an electrical signal through the tip, intended to damage hair roots and prevent new hair from growing from the same root.

• Molecular tweezers are noncyclic host molecules that have two arms capable of binding guests molecules through non-covalent bonding.

• Stamp tweezers or Stamp tongs are specially designed tweezers used for handling postage stamps.

[edit] References