Today, researchers at the Massachusetts Institute of Technology (MIT) designed a method for grafting nanoscale electronic devices onto floating microparticles for monitoring, from the gases in various environments to the internal workings of the human digestive system.
Last week at the American Chemical Society National Conference and Exposition, Michael Stella, professor of chemical engineering at the Massachusetts Institute of Technology and researcher Volodymyr Korman of the research team introduced them to use van der Waals forces (atomic and molecular The formation of a bond between them, the force that brings them closer together allows the electronics made of two-dimensional (2D) materials to adhere to the floating particles.
Strano and Coman used two-dimensional materials, molybdenum disulfide and tungsten diselenide (a transition metal dichalcogenide material) to make three discrete electronic devices: a power source capable of converting light into electric current; capable of detecting molecules Sensors; and memory devices that can retrieve data collected by sensors.
For power supplies, the researchers combined molybdenum disulfide with tungsten diselenide to form a pn heterojunction as a photodiode. This ubiquitous pn junction constitutes solar cells, light-emitting diodes, photodetectors, and lasers. The main part.
In explaining how the device converts light into electric charge, Coman said: 'Molybdenum disulfide is oxidized during the preparation process. The thin oxide layer of the material has the ability to store charge. When a threshold voltage is applied, molybdenum disulfide captures the charge and Change its resistance and switch to a different state.'
The sensor device demonstrates the strength of 2D materials because their atomic thinness is highly sensitive to changes in their electrical resistance. In this case, the researchers used a single layer of molybdenum disulfide to create a chemical in which the resistance of the material Changes with the presence of molecules.
The last electronic component, a memory device, was not always proven to be easily fabricated from 2D materials. But earlier this year, researchers at the University of Texas at Austin discovered a method that passes A memory device was fabricated by sandwiching a layer of molybdenum disulfide with a layer of atomic layer thickness, and the resulting device was found to have a memristor resistance. The basic structure of the device developed by the MIT team was to sandwich an atom of molybdenum disulfide between the two electrodes. Layer. One of the two electrodes is made of silver and the other is made of gold. According to Coleman, the memory device was modeled on the basis of research published on Nature Materials in 2015.
According to Coleman, the three devices are all independent, but they are all integrated in one chip. 'Modularization is the goal of our efforts so that we can exchange, increase and decrease each component.'
After the electronics are ready, the team needs to find the perfect microparticles and attach their 2D electronics to it. They are placed on micron-sized particles called the SU-8. The key feature of the particle is that it is a colloid. Particles, can be suspended in suspension.
The researchers found that they can propel particles containing nano-electronic devices to run in the form of aerosols, with particles traveling up to one meter. In physics experiments, researchers pushed their micro-robots to simulate gas pipelines to detect carbon. Particles or volatile organic compounds.
In order to collect the micro-robots after walking along the gas pipes, the researchers added small mirrors to them to see the micro-robots through their light reflections. The micro-robots have a metal connection and may download them once collected. Stored information.
Although the analog gas pipeline was the first test, researchers are also investigating the potential of using these devices as monitors for human digestive systems.
According to Coleman, the goal of future work will be to expand the library of electronic components that can be integrated on the chip.
He added: 'We will apply these different machines to different applications, such as the human digestive system, large area monitoring, extended pipeline monitoring and geological exploration.'