Gel condom to "empower women"

A new gel could make a "vaginal condom" that would physically entrap semen and anything it contains, including sperm and viruses such as HIV. The gel is liquid as long as it is in contact with the acidity that is normal in a vagina, but will turn solid when it encounters semen, which is slightly alkaline. Any particles wider than 50 nanometres – including sperm, HIV and other viruses such as the herpes virus and the papilloma virus, which causes cervical cancer – are trapped, so the gel could double up as both a protectant and a contraceptive. New Scientist