95 Essays on Infinite Lifespans   Raymond Kurzweil them with substances such as DNA, proteins or drugs. [3] There are already at least four major scientific conferences on bioMEMS and other approaches to developing micro- and nano-scale machines to go into the body and bloodstream. Ultimately,  the  individualized  nutrients  needed  for  each person will be fully understood (including all the hundreds of phytochemicals from plants) and easily and inexpensively available, so we won’t need to bother with extracting nutri- ents from food at all. Just as we routinely engage in sex today for its relational and sensual gratification, we will gain the opportunity to disconnect the eating of food from the func- tion of delivering nutrients into the bloodstream. This technology should be reasonably mature by the 2020’s. Nutrients will be introduced directly into the bloodstream by special metabolic nanobots. Sensors in our blood and body, using wireless communication, will provide dynamic infor- mation on the nutrients needed at each point in time. A  key  question  in  designing  this  technology  will  be  the means by which these nanobots make their way in and out of the body. As I mentioned above, the technologies we have today, such as intravenous catheters, leave much to be desired. A significant benefit of nanobot technology is that unlike mere drugs and nutritional supplements, nanobots have a measure of intelligence. They can keep track of their own inventories, and intelligently slip in and out of our bodies in clever ways. One scenario is that we would wear a special ‘nutrient gar- ment’ such as a belt or undershirt. This garment would be loaded with nutrient bearing nanobots, which would make their way in and out of our bodies through the skin or other body cavities.