Professor Charles Lieber and colleagues have used nanowires to create a transistor that is so small it can be used to enter and probe cells without disrupting the intracellular machinery; these nanoscale semiconductor switches could even be used to possibly enable the two way communication with individual cells.
Lieber has been working for over a decade on the development, design and synthesis of nanoscale parts that have enabled the creation of these tiny electronic devices. Creating this biological interface of a nanoscale device capable of communicating with a living organism has been a tricky project, the problem was being able to insert a transistor constructed on a flat plane into a 3D object of a cell perhaps 10 microns is size, wherein piercing the cell wasn’t enough because such a transistors need a source of wire from which electrons flow and drain a dire through which they are discharged.
The key was to figure out how to introduce two 120 degree bends into a linear wire to create a hairpin configuration with the transistor near the tip. The nanowire probes were integrated with a pair of bimetal layered interconnects; joining strips of 2 different metals that expand at different rates when temperatures change to as is in thermostats, to lift the transistor up and out of the flat plane in which it was created.
Inserting their tiny device into a cell was not as easy, as pressing hard enough to disrupt the cell membrane killed the cell fairly quickly. When the hairpin nanowire device was coated with a fatty lipid layer the device was easily pulled into the cell via membrane fusion which is the process related to the ones that cells use to engulf pathogens. Lieber explains this innovation is important because it indicates that when a man made structure is as small as a virus it can behave the way biological structures do.
Preliminary testing of the tiny nanodevice indicates that it could be used to measure activity within neurons, heart cells and muscle fibers among others, and it could also measure two distinct signals within a single cell simultaneously, or even the workings of intracellular organelles.
Because a transistor allows for the application of a voltage pulse this tiny device may even one day be able to provide a base for a hybrid biological digital computation or deep brain stimulation for those with conditions such as Parkinson’s disease, or it may even serve as an interface for a prosthetic that requires information processing at the point where it attaches to the user. As with any innovation such as this, the uses for such a device are only limited by imagination, for better or worse, whatever the case may be. Regulations for safety will undoubtedly need to be made before it is used in the future.
“Digital electronics are so powerful that they dominate our daily lives. When scaled down, the differences between digital and living systems blurs, so that you have an opportunity to do things that sound like science fictions– things that people have only dreamed about,” says Lieber.
