Exploration and characterization of the memcapacitor and memristor properties of Ni–DNA nanowire devices

A 2-μm-long Ni ion-chelated DNA molecule (Ni–DNA) was found for the first time to possess both memcapacitor and memristor properties; this Ni–DNA molecule is known as a dual memory circuit element (memelement). As a memelement, the state of impedance on Ni–DNA is proportional to the unit number of Ni ions containing a base pair complex (Ni–bp), which is determined by the previously applied external voltage. Interestingly, the impedances of Ni–DNA change in response to a change in the sweeping frequencies of the external bias. Our simulation results also indicate that changes in the effective resistance and capacitance of Ni–bp may be attributed to changes in the Ni ion redox species in the Ni–bp of a Ni–DNA nanowire. Therefore, the working mechanism of a nanowire-type memcapacitor and memristor is revealed. In summary, the Ni–DNA nanowire is shown to be a multi-dimensional memory device, whose memory state depends on the length of DNA and applied external voltages/frequencies. A DNA-based nanowire has the electronic properties required for a novel computer known as a memcomputer, show a team from Taiwan and the USA. Memristors and memcapacitors are devices whose resistance and capacitance depend on their previous electronic state. They are the building blocks of a so-called memcomputer, which processes information in a similar way to the human brain. By using DNA origami and self-assembly, Chia-Ching Chang from the National Chiao Tung University and co-workers incorporated nickel ions into DNA and demonstrated electronic memory effects. Specifically, they created a 2-micrometer-long DNA molecule chelated with nickel ions and showed that this nanowire has both memcapacitor and memristor properties. Simulations of the device indicated that these useful characteristics are a result of voltage-driven changes to the nickel ion redox species. Ni ions can be aligned by a double-stranded DNA and form a Ni–DNA nanowire. By integrating with the semiconductor circuits it becomes a novel molecular device, which is the first real dual memelement that exhibits functionalities of novel resistor and capacitor with memory, and redox-induced negative differential resistance (NDR) properties. The working mechanism of this novel device is similar to the memcomputing in brain.