Scientists in Australia have developed a sperm-sorting machine that may help infertile men to become fathers.

The device filters out sperm with DNA damage associated with infertility and a raised risk of childhood cancers.

“Mechanised sorting should be particularly useful when a would-be father is older, or is a heavy smoker or has been exposed to pollution in the workplace - all factors that increase this type of DNA damage,” New Scientist magazine said on Wednesday.

Fertility clinics centrifuge semen to increase the concentration of the densest sperm and raise the odds of fertilising an egg. But it is a time-consuming process and does not identify damaged sperm.

The new machine, developed by John Aitken and Chris Ainsworth of the University of Newcastle in New South Wales and its commercial partner Life Therapeutics of Sydney, is based on the principle that sperm with the most negatively charged membranes have the least DNA damage, according to the magazine.

The scientists believe sperm with negatively charged membranes have matured normally.

Smaller than a shoebox, the sperm sorter consists of two chambers separated by a filter. After the sperm is injected into the first chamber a voltage is applied across the filter to move sperm to the second chamber. “In preliminary tests, using semen from medical students, the 20 percent of sperm that made it into the second chamber had only half as much DNA damage as the sperm left behind,” New Scientist said.

“Other tests suggest that the sorter is equally efficient at pulling sperm with less DNA damage from the semen of men with fertility problems,” it added.

How efficient the sorter is at selecting good sperm will be tested in two clinical trials of women undergoing IVF (in vitro fertilisation) treatment in Australia later this year.