I have been using biological technology in short stories for about 7 years now and I have thought that the next revolution in cybernetics would be an organic one for at least 20 years.
IBM announced today that it has demonstrated using “DNA origami” to create biological cybernetic structures that are analogous to silicon based semiconductors. The advantages of using DNA are the very small scale, and the low cost of production. DNA is a substance that copies information naturally with very little encouragement. It is stable of long periods of time and it is easy to create.
A cubic centimeter of DNA has the potential to store 10 terabytes of data.*
I will guess, though, that speed of access will be an issue. Sending in messenger RNA to query DNA data stored in nucleic acid bonds will be very slow. The announcement sort of hinted that data had been stored, but failed to mention if it “write only memory” or if the data could be retrieved in a reasonable time.
I always felt that biological memory systems would be large arrays of crystalline proteins with metallic bonds that could be directly attached to leads and generate micro-voltages. These would be generally as dense, but would incorporate logical structures such as nor gates that could be used to directly access parts of the crystal at nanosecond speeds, or even provide computational functions.
*(data density of DNA, from a Google search, is 1 bit per cubic nanometer. A nanometer is 10^-9. A cubic meter then is 10^18 bits. A CC is 1/10,000 cubic meters so a CC is 10^14 bits or about (with parity & checks) about 10^13 bytes = 10 terabytes.)