Scanning Probe Microscopy Laboratory |
Quartz Tuning Fork Sensors Laboratory
At the SPM and QTF laboratories, Ph.D. research scholars, M.Tech dissertation candidates, and interns carry out research in the domains of nano-materials for EMI shielding and sensors, electronics for QTF-based sensors, and QTF sensors for breath analysis and gas detection.
Electromagnetic Interference Shielding
EMI shielding refers to the reflection and/or absorption of EM radiations using a material; the material acting as a shielding material prevents the penetration of radiations of high frequencies such as radio waves. Nanomaterials are highly sought after for their immensely tunable material properties which result in good shielding capabilities, not only in the microwave regions but also in other regions of the EM spectrum. E.g., reduced graphene oxide can be modified and conjugated with magnetic materials to obtain electrical and magnetic properties tailor-made for varied applications.
Metamaterials as sensors and electromagnetic absorbers
The concept of negative refractive index was introduced by Vaselago which was realized by using metallic wires and split-ring resonators to separately demonstrate negative permittivity and negative permeability materials, respectively, in the 1990s by Pendry et al. Later, Smith et al. experimentally realized these structures in the microwave regime by using both the structures simultaneously in specific ways to produce Left-Handed Materials (LHMs). Such materials have unique proper- ties which depend on the “meta atomic structure”, rather than the constitution of the materials.
Quartz Tuning Fork-based Sensors
QTFs are U-shaped quartz crystal mechanical transducers whose mechanical properties can be monitored by measuring the changes in resonant frequency which are identified in the form of an electrical signal. The high-quality factor (nearly 10 000 in vacuum and about 1000 in air) and affordable price (less than $0.05) allow the QTFs to be accurate as well as affordable. A polymer element atop the tines of the QTF acts as the sensing element for the QTF sensor and causes a change in the resonant frequency based on its interaction with the analyte and is used for volatile organic compound sensing and breath analysis
Scanning Probe Microscopy
Scanning probe microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. Forces acting between nano-sized cantilever tip and sample are measured using this instrument. Research interests lie in applications including Electrostatic Force Microscopy, Magnetic Force Microscopy, Conductive Atomic Force Microscopy, Amplitude Modulated- Frequency Modulated Microscopy, Force Spectroscopy, Piezoelectric Force Microscopy.
Microwave absorption properties of reduced graphene oxide strontium hexaferrite/poly (methyl methacrylate) composites. Acharya et al. Nanotechnology 29 (2018) 115605 (14pp)
Modified graphene as a conducting ink for electromagnetic interference shielding. (a) Ink components. (b) Stable samples of inks of (i) rGO (ii) rGOFe3O4 (iii) rGONi. EMI shielding effectiveness of the ink coatings over the X band. S Parmar et al. J. Phys. D: Appl. Phys. 52 (2019) 375302
Polymer modified quartz tuning fork (QTF) sensor array for detection of breath as a biomarker for diabetes. Schematic representation of the testing procedure and Sensor Parameters a) change in frequency, b) change in drop time recovery time, and c) change in rate of drop in frequency and change in rate of recovery for all the sensors. S. Parmar et al. Sensors and Actuators: B. Chemical 358 (2022) 131524
Metamaterial Microwave Absorber (MMA) for Electromagnetic Interference (EMI) Shielding in X‐Band. Simulated and fabricated Metamaterial Absorber with spoke and wheel structure and its simulated and experimental S parameters vs. frequency. Mishra et al. Plasmonics 16, 2061–2071 (2021).
Electrostatic Force Microscopy. (a) Phase vs voltage spectra calculated from EFM images of the surface of MoS2, hBN, and biphasic MoS2-hBN film grown on c-Al2O3 for the applied voltages (−5 to +5 V) (b) EFM phase shift of MoS2 -hBN . (a) Topography and EFM images of MoS2-hBN film at tip bias 4 V (b) before and (c) after charging with -10 V. Parmar et al. Physical Review Materials 3, 074007 (2019)