A German firm has developed a prototype vehicle designed to more effectively deliver disease-fighting drugs without damaging healthy tissue. As Wired (Sept. 2000) reports, the 0.5-millimeter-by-4-millimeter "subdermal micro-U-boat" would be injected into the patient’s bloodstream and deliver its treatment cargo by using sensors to seek out the heat
generated by infections or the pH differences caused by cancer. The probe would be powered by converting raw materials in the blood into energy.
Wired (Sept. 2000)