There you have it, a blood-cell-sized memory device, a whopping 160,000 memory bits, “arranged like a large tic-tac-toe board,” and composed of 400 silicon wires crossed by 400 titanium wires, each 16 nanometers wide. UCLA says that the large-scale molecular memory microchip recently developed by its and Caltech’s scientists will find applications in implantable medical and miniaturized diagnostic devices.
The 160-kilobit memory device uses interlocked molecules manufactured in the UCLA laboratory of J. Fraser Stoddart, director of the California NanoSystems Institute (CNSI), who holds UCLA’s Fred Kavli Chair in Nanosystems Sciences and who was awarded a knighthood by Queen Elizabeth II less than a month ago…
The research published in Nature describes the fabrication and operation of a memory device. The memory is based on a series of perpendicular, crossing nanowires, similar to a tic-tac-toe board, with 400 bottom wires and another 400 crossing top wires. Sitting at each crossing of the tic-tac-toe structure and serving as the storage element are approximately 300 bistable rotaxane molecules. These molecules may be switched between two different states, and each junction of a crossbar can be addressed individually by controlling the voltages applied to the appropriate top and bottom crossing wires, forming a bit at each nanowire crossing…
A rotaxane is a molecule in which a dumbbell-shaped component, made up of a rod section and terminated by two stoppers, is encircled by a ring. It has the potential to be a molecular abacus. The bistable rotaxanes behave as switches by incorporating two different recognition sites for the ring, and the ring sits preferentially at one of the two, said Stoddart, leader of the UCLA team. The molecule can act as a switch provided the ring can be induced to move from one site to the other site and then reside there for many minutes. The bistable rotaxane molecules used in the crossbar memory can be switched at very modest voltages from an “off” (low conductivity) to an “on” (high conductivity) state. The stoppers for the rotaxane molecules are designed to allow the molecules to be organized into single-molecule-thick layers, after which they are incorporated into the memory device, Stoddart said…
“For this commercial dream to be realized, many fundamental challenges of nano-fabrication must be solved first,” Stoddart said. “The use of bistable molecules as the unit of information storage promises scalability to this density and beyond. However, there remain many questions as to how these memory devices will work over a prolonged period of time. This research is an initial step toward answering some of those questions.
“Using molecular components for memory or computation or to replace other electronic components holds tremendous promise,” Stoddart said. “This research is the best example — indeed one of the only examples — of building large molecular memory in a chip at an extremely high density, testing it and working in an architecture that is practical, where it is obvious how information can be written and read.
More from UCLA, Caltech and the National Science Foundation…