We may have seen the future of vacuum cleaners, folks. While robot vacuums are pretty cool, going about their dust-sucking business with total obedience and autonomy, they still have to retreat back to a charging station once in a while to restock on power before heading out again.Not so Limbo, the robot vacuum cleaner that recharges itself while it goes about its business by using power generated by the very dirt it is there to remove.Created by industrial designer Elliot Cohen, Limbo is sadly just a concept machine at present, created for the 25th anniversary of Casabella, and exhibited at the 2013 International Housewares Show held recently in Chicago."The robot is a concept to inspire and push the limits of design and engineering for the future," says Cohen, and it could very well be a test for manufacturers to get working effectively.Its wheels can be adjusted according to the task needed, such as climbing stairs and getting close into walls to suck up the more stubborn dirt - something circular robot vacuum cleaners can struggle with.But it is the fuel-cell that would most likely require the most care (and money) in the manufacturing process. It uses a process called microbial electrolysis. Microbial fuel cells (MFCs) have been in existence for a considerable time now, but have rarely been used in consumer products. In simple terms, they generate electricity from the degradation of organic matter - your household dirt, in this case - so, Cohen suggests, one could be used to recharge a conventional battery as the Limbo works.Whether we see this come to fruition any time soon is debatable, but still, great idea.