Virus 'hybrids' can act as nanoscale memory devices

 作者:祖囔羸     |      日期:2019-02-28 02:18:06
By Belle Dumé A new type of memory device has been made by researchers in the US and Italy by attaching individual viruses to tiny specks of semiconducting material called quantum dots. The “hybrid” material could be used to develop biocompatible electronics and offer a cheap and simple way to make high-density memory chips, the researchers say. Some biological materials react to inorganic molecules and researchers have already exploited this phenomenon to build nanoscale devices that can be used as biosensors (see Molecular ‘switch’ connects biology to silicon). Mihri Ozkan of the University of California at Riverside and colleagues have now gone a step further by making a device that can also store digital information. “Interactions between organic and inorganic particles are quite fascinating,” team leader Ozkan told New Scientist. “In our case, finding the memory effect was quite unexpected because each nanoparticle does not have any memory characteristics on its own, but only when connected as a hybrid.” Ozkan and co-workers began by depositing cosahedral cowpea mosaic viruses (CPMV) on quantum dots (made of cadmium selenide and zinc sulphide) using different binding sites on the virus’ capsid, or outer shell. CPMV, a plant virus that is harmless to humans, is about 30 nanometres across and consists of a capsid with an RNA core. Next, the researchers embedded the hybrids into a polymer matrix and sandwiched them between two conducting electrodes for testing. They found that each hybrid unit can be operated as a memory device with conductive states that can be switched between high and low, corresponding to a 1 and a 0, by applying a low voltage. These states are “non-volatile”, meaning data is stored even when the power is switched off. The scientists say the device works by transferring charge from the CPMV’s capsid to the nanoparticle when an electric field is applied. The thin zinc sulphide capping layer on the quantum dots stabilises the trapped charges so that they can be stored. Ozkan says that, in theory, this could lead to high-density storage, because each individual hybrid could be a single storage unit and millions would fit into a space just a few centimetres square. The researchers have successfully performed a number of read-write-erase cycles on their single hybrids, and are now looking at how inorganic particle size affects the viruses and the final memory effect. Other applications can be envisaged too, says Ozkan, such as environmental sensing, because more functionality can be added on to the virus template. More exotically, such a system could eventually perhaps be used to record its journey through sites of interest in the human body – for example, diseased tissue or arteries. “In Star Trek terms, the hybrids could act like nanomachines or nanorobots built for treating disease,” quips Ozkan. Journal reference: Applied Physics Letters (DOI: 10.1063/1.2742787) More on these topics: