Browsing by Subject "Nanoelectromechanical systems (NEMS)"

Now showing 1 - 3 of 3

Open Access
Development of nanoelectromechanical systems functionalized by vacuum organic thermal evaporation and their gas sensing applications
(2017-01) Karakan, Mustafa Çağatay
Nanoelectromechanical systems (NEMS) are an exquisite sensor technology which is also potentially low-cost since it can be measured electronically and large scale produced using semiconductor fabrication techniques. Since they are extremely sensitive due to their miniscule dimensions and respond very fast due to their high resonance frequencies, these systems can be used as novel mass sensors or gas detectors. However, a functional polymeric layer that is selective to the analyte of interest is required to allow recognition by these sensors and use them as gas concentration detectors. This work focuses on fabrication of high frequency NEMS resonators, their chemical functionalization and gas sensing applications. Nanomechanical resonators with fully integrated transduction capabilities are fabricated in collaboration with Sabanci University, by using electron-beam lithography and reactive ion etching techniques. Representative micro gas chromatography columns are fabricated by utilizing deep reactive ion etching process. By employing an electronic circuit and downmixing technique, resonant responses of these sensors are measured. First five mechanical modes are observed in open-loop sweeps and up to two modes were tracked simultaneously by implementing a phase locked loop circuitry. Sub-attogram (10-18 g) mass sensitivity is achieved under ambient conditions. Different approaches were adopted for depositing polymer on NEMS and vacuum organic thermal evaporation was chosen due to its repeatability. Effects of functionalization process and thickness of the polymeric film on nanomechanical resonators are analyzed and negligible downgrade on performance of nanomechanical sensors is observed with this technique. A gas bubbler based vapor generation system was constructed and a microliter chamber for nanomechanical resonators is developed to generate and deliver volatile organic compounds at various concentrations to NEMS sensors functionalized by vacuum organic thermal evaporation. Initially adsorption of water-vapor and subsequent desorption from the sensor surface are successfully observed by tracking the frequency shift via open and closed loops. Then, isopropanol alcohol is used as a test gas and detected by NEMS resonators functionalized with poly (4-vinylphenol). Linear relationship between gas concentration and resulting frequency shift is observed. Finally, possible improvements to enhance selectivity of the NEMS sensor and allow faster recognition are discussed.
Open Access
Nanomechanical motion transducers for miniaturized mechanical systems
(MDPI AG, 2017) Kouh, T.; Hanay, M. S.; Ekinci, K. L.
Reliable operation of a miniaturized mechanical system requires that nanomechanical motion be transduced into electrical signals (and vice versa) with high fidelity and in a robust manner. Progress in transducer technologies is expected to impact numerous emerging and future applications of micro- and, especially, nanoelectromechanical systems (MEMS and NEMS); furthermore, high-precision measurements of nanomechanical motion are broadly used to study fundamental phenomena in physics and biology. Therefore, development of nanomechanical motion transducers with high sensitivity and bandwidth has been a central research thrust in the fields of MEMS and NEMS. Here, we will review recent progress in this rapidly-advancing area.
Open Access
Vapor sensing of colorectal cancer biomarkers in isolation by bare and functionalized nanoelectromechanical sensors
(Institute of Electrical and Electronics Engineers, 2023-08-04) Karakan, M. C.; Ari, Atakan B.; Kelleci, M.; Yanik, C.; Kaya, I. I.; Tastan, O.; Hanay, M. Selim
Small dimensions and high resonance frequencies render nanoelectromechanical systems (NEMS) sensitive mass detectors. Mass detection capability can be used to sense chemicals in the gas phase by functionalizing the device, usually with a polymeric film. The performance of NEMS-based gas detectors in breath analysis applications depends crucially on the selectivity between selected functionalization layers and targeted biomarkers. Here, we report the detection of four colorectal cancer biomarkers at parts-per-million concentration levels, when introduced in isolation to the sensor system within a dry nitrogen stream. The biomarkers, 3-methylpentane, cyclohexane, nonanal, and decanal, were then discriminated from each other by using the combined response of three NEMS devices: one bare device, and two devices coated with either poly(ethyleneoxide) or poly(caprolactone). Our results indicate that bare NEMS are more responsive to high molar mass biomarkers, whereas functionalized sensors are more responsive toward more volatile biomarkers. Considering the inherently fast response times and minuscule limits of detection of NEMS devices, the combined response of differentially coated sensors can be used as the main sensing element to identify and distinguish cancer biomarkers in human breath.