With more biology than robotics, researchers at University of Tokyo harvested eggs from African Clawed Frogs to build inexpensive olfactory sensors. DNA from fruit flies and moths were added to stimulate production of the sensors known to be good at detecting certain molecules, then electrodes were attached to capture the receptor's output. Now for the "Robot" part - results from the sensors are read by software on a PC and a simple actuator was used to cause a robotic mannequin head to shake back and forth adding impact to the experiment. See the PDF for the full scoop.