Microbots 670 millionths of a metre tall and 170 to 240 millionths of a metre wide - no bigger than a full stop - could someday be used to move single cells or capture bacteria, their Swedish inventors say. The tiny bots make use of conducting polymers in their joints to move around. These polymers, dubbed ‘micromuscles’, absorb charged ions from the surrounding liquid, or shed them, depending on the electrical charge applied through tiny wires connected to the robot. Absorbing or shedding ions causes the polymers to swell or shrink, while the gold layer remains the same thickness. The swelling or shrinking of the robot joints causes them to bend when various charges are applied.The robots might be used as microsurgical instruments, Jager said. Previous microrobots have included such things as electronic devices featuring rods and levers, artificial flying insects and a walking silicon microrobot, but none could operate in water, Jager continued. Or, he added, these microrobots might be used to build other microdevices, just as cars are built by robots. In medicine, the robots could move a single cell from one point to another, he said. The microrobots, resemble a tiny human arm complete with flexible elbow and wrist joints and hands with two to four fingers. Bending of the polymer-gold layers causes the robot arm to flex at its elbow, bend the wrist and close and open the fingers to grasp it, and the bots have already been used to pick up and move tiny glass beads invisible to the unaided eye. Currently they are rooted to the spot, but Jager said he could foresee a time when they are made mobile. The devices can work while submerged in such liquids as blood, urine and cell-culture medium, suggesting possible uses in biotechnology. The inventors said in a statement that one day the robots might be usable to pick up tiny biological items and move them to an analysis station, and in groups to assemble microstructures.