Synthetic biology deliberately equates genetic networks to electronic circuits, cells to machines, organisms to factories. In synthetic biology, every living can be thought of as a cyborg, a living machine that can be manipulated, changed to meet our needs, parts swapped in and out like a computer. Some projects in synthetic biology and biologically inspired engineering hope to bring the analogy a step further, combining biological and actual electronic and mechanical components into a single engineered unit, with the goal of essentially making tiny autonomous cyborgs.
There are a lot of examples of biomimetic robots, robots that have components built to resemble biological structures but made of non-biological materials. Joseph Ayer's group at Northeastern builds biomimetic underwater robots that look and act like lobsters or lampreys, that have electronic brains built to function the way that networks of neurons do in the brains of animals. Using complex signal processing they can swim around and follow different stimuli.
None of these robots, however, use actual biological components (yet). Biological engineers and robot scientists are currently thinking of ways where the unique properties of living cells could be used as components in small robots. The Cyberplasm project aims to do just that.
In this fish-shaped robot, the eyes are made of synthetic biological sensors, engineered strains of yeast or bacteria that are able to sense chemicals in the water and send a signal to the electronic "brain." These electronic circuits then send signals to muscle cells engineered to respond to signals coming from an electronic "nerve" rather than a biological one, causing the fish to swim towards the chemical signal.
I have to admit that when I think about these robots sometimes I feel like I'm in that part of Terminator II when the skynet scientist are inadvertently setting the course for their own demise at the hands of killer robots, but at the same time I think they are just totally amazing and fascinating. These are hardly self-replicating murderous robots (they're hardly more than ideas at this point), and technology that incorporates biological systems that can do things more efficiently and with less energy than electronic or mechanical components can be enormously beneficial. Being able to create better interfaces between electronic and biological components may also help in designing better medical devices like pacemakers, brain stimulation devices for treatment of Parkinson's and other serious chronic neurological diseases, or devices that can monitor health and release drugs precisely when needed. They're also just plain cool.