From microelectromechanical systems (MEMS) technology, which miniaturized electrical components down to the order of micrometers (μm), engineers of tinyness have only one direction left to explore: smaller.
Image source: NIMEDIA/Shutterstock.com
Nanoelectromechanical Systems (NEMS) research and development is shrinking electrical components and mechanical parts down to the nanometer (nm) scale. Today, scientists are making devices more functional and smaller as the NEMS market grows.
A brief history of tiny, functional devices
The history of NEMS devices begins in the early days of miniaturization, when the first metal-oxide-semiconductor field-effect transistor (MOSFET) was manufactured in 1960 with a gate oxide thickness of just 100 nm. Two years later, the same researchers fabricated a transistor using thin layers of gold, just 10 nm thick.
The first MOSFET with an oxide thickness of 10 nm was demonstrated in 1987. Two years later, starting in 1989, research was carried out to develop the channel length of multi-gate MOSFETs to below 20 nm. This was achieved in 1998 with devices with a channel length of 17 nm.
Very large scale integration (VLSI) NEMS devices entered the market with the new millennium in 2000, with a memory device consisting of a heat-sensitive AFM tip array and a deformable substrate. VLSI is the creation of integrated circuits that combine millions of transistors on a computer chip.
In the 2000s, both the market and the areas of application for NEMS devices have expanded, and research continues to shrink electromechanical systems to ever-tinier limits.
NEMS devices are based on advances in nanotechnology
NEMS devices, like other examples of nanotechnology, operate in nm-scale dimensions. This means they have extremely low mass, high resonant frequencies, and can operate according to the non-intuitive laws of quantum mechanics by exploiting high surface-to-volume ratio or zero-point motion.
Manufacturers also use common nanotechnology manufacturing techniques and methods to create NEMS devices.
Top-down manufacturing approaches such as optical fabrication, e-beam lithography, and heat treatment allow for extensive manufacturing control at the expense of relatively low resolution.
Bottom-up approaches that use chemistry to let components self-assemble molecule by molecule. This allows manufacturers to produce smaller structures, although it is more difficult to control the outcome of the manufacturing process.
As in other areas of nanotechnology, hybrid approaches can also be used to integrate different components. Carbon nanotube nanomotors are an example of a NEMS device made using hybrid top-down bottom-up manufacturing.
Applications for NEMS devices
In theory, NEMS technology can be applied to any electromechanical system. Current applications include NEMS accelerometers and NEMS sensors that can detect the presence of chemical substances in the atmosphere.
A major application for NEMS technology is in the tiny stylus tips used in atomic force microscopes. NEMS introduces smaller, more efficient sensors to detect even fainter atomic forces and chemical signals in state-of-the-art atomic force microscopy (AFM) today.
NEMS-based cantilevers are also used in various other sensor and scanning probe devices and can operate at very high frequencies (VHF) of around 100 MHz.
NEMS relays can replace traditional solid-state logic “switches” in the next generation of computers. Although they are slower than solid-state alternatives, they don’t lose power and consume little power.
Groundbreaking NEMS research today
NEMS research is already a very new and advanced field, but scientists continue to push the boundaries of how far they can take this technology.
In a recent example, researchers fabricated a nanoscale piezoresistive transducer by suspending silicon on two layers of graphene ribbon. The NEMS transducer’s performance was comparable to transducers currently used in accelerometers, and the researchers said it would improve the performance of currently available NEMS-based accelerometers.
Another pioneering research avenue for NEMS technology is bionanoelectromechanical systems (BioNEMS), which combine biological elements with synthetic structures. BioNEMS devices have applications in medicine as well as nanorobotics, with the potential to function as proteins, DNA, and even nanoscale autonomous robots.
The future of NEMS devices
Currently, the NEMS market is still in its infancy. NEMS devices have not yet enjoyed widespread acceptance, and in many cases no clear commercial application has emerged for pioneering research in this area.
Some of the biggest challenges facing a burgeoning NEMS industry are the problems of low-yield production techniques and unreliable manufacturing, resulting in large variations in quality between devices.
However, many researchers and industrial developers are now turning their attention to practical applications, and this context is expected to change significantly in the coming years.
Futuristic applications in advanced lightning-fast computing, wearable technology, biomedicine, and nanorobotics may be just a few years away. The future will be smaller.
Continue reading: Leveraging Park System’s SECCM for nanoscale electrochemical studies
References and further reading
Ali, U.E. et al. (2022). Real-time nanomechanical property modulation as a framework for tunable NEMS. nature communication. https://doi.org/10.1038/s41467-022-29117-7.
Despondent, M. et al (2000) VLSI NEMS chip for parallel AFM data storage. Sensors and actuators A: Physical. doi.org/10.1016/S0924-4247(99)00254-X.
Ekinci, KL, et al. (2004) Ultrasensitive nanoelectromechanical mass detection. Applied physics letters. doi.org/10.1063/1.1755417.
Fan X et al. (2019) Floating mass graphene ribbons as transducers in ultrasmall nanoelectromechanical accelerometers. nature electronics. doi.org/10.1038/s41928-019-0287-1.
Parsa, R. et al. (2013) Side-actuated platinum-coated polysilicon NEM relays. Journal of Microelectromechanical Systems. doi.org/10.1109/JMEMS.2013.2244779.
Shafagh, RZ, et al (2018). E-beam nanostructuring and direct-click biofunctionalization of thiol-ene resist. ACS nano. doi.org/10.1021/acsnano.8b03709.
Heflin, JR (2004) Introduction to nanoscience and technology. Springer, New York. doi.org/10.1007/b119185.