A tiny implant could release a daily dose of medicine for up to a year, according to scientists.
The drug release chip is implanted into the body
Researchers at Edinburgh University are developing the system, which would include micro-reservoirs of concentrated drugs.
Scientists said it could be the next development in the fight against cancer, and could even provide an alternative to chemotherapy.
That process is currently delivered intravenously.
It often leads to side-effects such as hair loss and nausea.
However, the implant would target the drugs to a site close to the tumour, ending the need for treatment sessions.
The drug release implant is powered and controlled by the patient via a wireless link.
The system uses an electrochemical reaction to remove a gold cap on the reservoir containing one dose of a drug. Wireless power transfer means there is no need for a battery.
The entire system can be contained in a package only a few millimetres across.
This enables it to be implanted into a wide range of locations within the body, such as the vitreous cavity of the eye, where it could release drugs to control chronic diseases such as glaucoma.
Stewart Smith, a research fellow in Edinburgh University's Institute of Integrated Micro and Nano Systems, said: "A low power, micro-scale drug delivery system such as this could have many potential benefits in the future for delivering medication to a localised area.
"Being able to develop such technology, which is wireless, will mean that the implants can be created on a minute scale without the need for bulky batteries."
The work has been funded by the Japanese company Senju Pharmaceuticals.