The use of metal scalpels is first documented by Hippocrates in 400 BC (Adams F. The Genuine Works of Hippocrates, Vol. II. London: Sydenham Society, 1849: 808.). A blade is characterized by its cutting ability and durability. The cutting ability is determined by the cutting edge radius, the roughness of the cutting edge, the hardness of the blade and the blade geometry. The less force (newtons) that must be applied to the blade to cut the material, the sharper the blade.
The blunt blade causes more tissue damage because it damages more tissue. Incisions made with a scalpel with a small cutting edge radius heal better than incisions made with a scalpel with a large cutting edge radius (Izmaĭlov GA, et al. Evaluation of the healing of skin wounds inflicted by steel scalpels with various degrees of sharpness Khirurgiia (Mosk). A sharp scalpel is the first requirement for good postoperative wound healing (Huebscher HJ, et al. The sharpness of incision instruments in corneal tissue. Ophthalmic Surg. 1989 Feb;20(2):120-3.).
Scalpel blades are usually made of stainless steel and have a cutting radius of 5 to 1000 nanometers (Polymeric Nanomaterials in Nanotherapeutics, Cornelia Vasile, ISBN: 9780128139325).
The diameter of a red blood cell is 7.5 micrometers (7500 nanometers). Diamond blades have a cutting radius of about 3 nanometers, but cost thousands of euros each. The cutting radius of a CO2 laser is 200 micrometers (200,000 nanometers).