A paper by the Hanay research group describing their recent invention of a new measurement technique was featured on the front cover of last month’s issue of ACS Nano, one of the leading journals in nanoscience and nanotechnology. The work outlined in the paper demonstrated the weighing of single nanoparticles and viruses under atmospheric conditions for the first time.
The research group, led by Asst. Prof. Selim Hanay of the Department of Mechanical Engineering, is headquartered in that department but also affiliated with UNAM (the National Nanotechnology Research Center at Bilkent University).
Mass spectrometry, the weighing of molecular structures for identification, is an important biological and environmental technique. Mass spectrometers were first invented by J.J. Thompson over a century ago; all versions to date have been able to operate only under vacuum conditions. But generating a vacuum requires bulky and expensive pumps, chambers and other components, requiring significant cost and space, thereby limiting use of the technique.
That is where the Bilkent breakthrough comes in. The new technique uses an emerging sensor technology, nanoelectromechanical systems (NEMS), that can measure the mass of nanoparticles via mechanical resonance. NEMS are thus fully functional mass spectrometers on a chip. However, since this type of mass spectrometer is composed of a tiny sensor, the transportation of analyte nanoparticles to it in an effective and efficient manner had constituted an insurmountable challenge. The Hanay group solved this challenge by inventing a self-focusing lens on the chip that can efficiently transport and focus the nanoparticles on the tiny NEMS surface.
“Our work enables NEMS mass spectrometers to perform rapid mass measurements outside the vacuum chamber,” stated Tufan Erdoğan, the lead author of the paper. “Consequently, we have opened the door for NEMS to also perform outside the lab, in the field, in the future.”
Mohammed Alkhaled, a PhD student and another co-primary author of the paper, noted that the research team went about resolving the nanoparticles-to-NEMS-sensor transportation issue using an “outside the box” approach. “The technique used in this work turned out to be simple yet very effective,” he said.
Junior graduate student and co-primary author Batuhan Emre Kaynak observed that the team’s “simple but delicate approach” to weighing single nanoparticles and viruses allowed them to work entirely under atmospheric conditions while avoiding many drawbacks such as inefficiency and bulky, expensive equipment.
Dr. Hashim Alhmoud, a Marie Skłodowska-Curie COFUND fellow and another co-primary author of the paper, put the work into perspective, declaring, “The simplicity and effectiveness of this approach to ion focusing is exquisitely elegant. This is a fully functional, self-biasing ion lens integrated on a chip. I believe this will have implications that are not limited to the world of pathogen screening, but will also be of significance for environmental sensing, rapid pharmaceutical drug discovery, on-site forensics trace analysis, and perhaps also geology and space science. Removal of vacuum requirements will no doubt lead to true handheld mass spectrometers in the near future. This is a very exciting time.”
Critical nanofabrication support was provided by SUNUM (the Sabancı University Nanotechnology Research and Application Center). Further collaboration with METU MEMS, Sabancı University FENS, and Prof. Aykut Özkul at the Ankara University Department of Virology and Biotechnology Institute helped in establishing the work. The work was supported by TÜBİTAK and the European Research Council.
The paper, titled “Atmospheric Pressure Mass Spectrometry of Single Viruses and Nanoparticles by Nanoelectromechanical Systems,” was published in the March 2022 issue of ACS Nano.