From interaction with bacteria, propulsion based on cells, in vivo medical applications to even intracellular applications, the rapidly expanding development of micro- and nanomachines with sizes comparable to or even smaller than mammalian cells, has led this field to advance from understanding of basic motion mechanisms to applications in living biosystems. A recent review highlights the recent efforts for and toward application of micro/nanomachines in living biosystems, including microorganisms, biological cells, and human body. Applications of micro- and nanomachines in living biosystems are reviewed from two aspects: their interaction with other microscopic organisms or biological units, and the efforts toward their application in the human body.
Researchers find magnetic helical nanomachines that mimic the swimming characteristics of E. coli bacteria to be particularly promising because of their extremely small size and their capability of navigating in various biological fluids like human blood. New work extends the possibility of using helical nanomachines as a tool to measure the localized mechanical properties of a heterogeneous environment that is ubiquitous in biological systems. This technique can be useful to gain valuable insights into the physiological changes of a cell in response to a disease or a drug, leading to better therapeutics.
The role of artificial nanomotors integrated with therapeutic capabilities is a very promising field for clinical applications of medical nanotechnology. Researchers now have demonstrated the intelligent design of nanomotors with a single coating of ferrite, which act as a spacer layer as well as providing therapeutic potential by magnetic hyperthermia. These motors can be remotely maneuvered. The team also tackled the problem of magnetic agglomeration associated with ferromagnetic nanomotors, which limits their biomedical application.
Researchers have utilized a rotating triboelectric nanogenerator (R-TENG) to enhance a polyimide nanofiber air filter for particulate matter (PM) removal. The nanofiber filter exhibits high removal efficiency for the PM particles with diameter larger than 0.5 microns. When working with the R-TENG, the removal efficiency of the filter is enhanced, especially in the region with the diameter of the particles in the PM smaller than 100 nm. This work may propose an approach of air cleaning and haze management by introducing TENGs to the filters.
A recent review article highlights the role of electrochemistry in synthesizing materials for self-powered micro- and nanodevices; the aspect of charge transfer and changes in electrochemical potentials for locomotion; control of self-propelled motion using electrochemistry and electric fields; and possible applications in electrochemical sensing and energy generation using micro- and nanoscale motion. The authors discuss various electrochemical techniques, which allow for the fabrication of large amounts of micro/nanorobots from diverse materials, with and without the use of templates.
Researchers show how spermatozoa can be useful parts of microdevices: As biocompatible propulsion source, but also entailing other functionalities such as their natural destiny for fertilization, their ability to respond to stimuli, or their ability to take up drugs open up fascinating new applications. They demonstrate first examples of using sperm cells as robotic components. The so-called spermbots are also systems that enable biophysical studies, e.g. of sperm motion in confinement.
Notwithstanding the progress in extracting renewable energy from many natural resources through nanotechnologies, some 60 research groups worldwide have now begun to develop triboelectric nanogenerators (TENGs) for harvesting energy from 'good (mechanical) vibrations' including human walking and ocean waves, which are otherwise wasted. Nanostructuring the materials in a TENG device amplifies the produced energy by increasing the contact area of the surfaces. Researchers have found a new way to scalably manufacture large area TENGs with a very high-throughput using off-the-shelf materials.
One way to construct useful molecular machines is to combine natural molecules - such as proteins or DNAs in our body - with synthetic molecules in order to control the functions of the natural molecules. Building on previous work that allowed to achieve complete control over on/off switching of the movement of a nanomachine, researchers in Japan have, for the first time, developed a molecular system which allows free control of the motion of single microtubules. The microtubules, tube-like structure with measuring 25 nm in diameter, could potentially serve as carriers of various molecular cargoes in future nano-transportation systems.