Problem Statement: Atomic Force Microscope (AFM) enables to map the topography of a surface while scanning it with a nanoscale tip. The topography is possible in nano-metric resolution due to the tip itself: When it stands in a nano-metric distance from the surface, several forces are interacting on it, such as Van der Waals forces, Casimir forces, capillary forces, and electric and magnetic forces. Due to the interactions between the scanned surface and the tip, when the tip approaches the surface, it is moved aside due to these forces. From the vibrations/moves of the tip, it is possible to map the topography of the scanned sample. The tip’s vibrations are measured by a laser beam, which illuminates it, and when the reflections change because of the vibrations, then the reading of the equipment changes accordingly.
When compared to AFM, Near-Field Scanning Optical Microscope (NSOM) provides an optical image (i.e. not a topographical/mechanical image) of the surface. Its tip extremity, which is significantly smaller than the optical wavelength, records evanescent waves reflected from the surface by tiny spatial structures, all significantly smaller than the optical wavelength, while the surface is illuminated by a light source coming from the tip itself or from an external lightening source. With the perception of the reflected light waves, NSOM catches the optical reflectivity of spatial structures. Through the tip’s scanning, a full map of the checked sample is obtained. The light captured by the tip is conducted to its backside to an optical fiber, connected to an optical detector, reading an electrical signal proportional to the captured light intensity in the tip.
In fact, both the microscopes provide nano-metric information of the scanned sample, so both of them share large usage in the domains of nanoscale measurements. However, they do provide different types of information. This is why it is very difficult to synchronize/coordinate between them, since we talk about the coordination between two different types of imaging. Both the microscopes are sensitive to vibrations due to their principle of action. Moreover, NSOM shares a low optical efficiency since the coupling of the evanescent waves to the extremity of the tip, and the light conduction to the detector standing at its back, is a non-efficient energy process.
The current project of combined AFM-NSOM tip comes to address and solve all above mentioned problems. By integrating the two microscopes to one unique system, while combining the two tips to one, which provides two types of images, we create two pictures without the need to synchronize or coordinate between them. The reason is because we get simultaneously two different and complementary readings from each checked spatial point. Due to the integration to one instrument, the dependence on the vibrations significantly decrease since there is only one unique tip, and not two influenced by the vibrations. With this new sensing method, we propose a nanoscale photodiode placed at the extremity of the scanning tip, where will occur the transformation of the reflected light from the surface into an electrical signal. This is also why the energy efficiency to the functionality of the NSOM becomes much higher than for a regular NSOM tip-system, and does not include any coupling of evanescent waves and their conduction of the backside optic fiber.
Beyond its actual potential, as part of preliminary research performed by the team, we have demonstrated additional directions of capabilities for the scanning combined-tip, such as sensitivity to polarization (polarimetry sensing), and more. This can bring to one combined instrument, sharing one unique tip, with enhanced sensitivity and multi-functional sensing capability for topography, reflected light, polarimetry and more.
This concept can become a technological platform for future developments, proposing high interest for the relevant industry. Described concept and technology have never been realized before we proposed them. They can be useful in the domain of materials and biology experiments performed in micro-gravity conditions, where the qualities of integration, reduced sensitivity to vibrations, and multi-functionality play a central role in the advantage of such system proposes when compared to experiments performed with several conventional and separated AFM and NSOM instruments.
This new core concept includes not only special technology, protected by patents, novelty and industrial applications, but also and mainly an expert team, combining knowledge and experience in complementary scientific domains, as well as a close collaboration with an industry.
Proposed Solution: An AFM-NSOM combined sensor has been developed, enabling both properties of AFM and NSOM scanning. This breakthrough was the recipient of a granted official US Patent #US11169176B2. Also, 12 related articles have already been published on this new device. Moreover, such capabilities are of high interest for SpacePharma Corporate, which is expert in launching small satellites performing physical and biological experiments in micro-gravity conditions. Associated with SpacePharma and colleagues from Bar-Ilan University (BIU), the whole team received two grants from the Israel Innovation Authority (IIA) in the Nofar Program. ALEO team is now working in high gear on the testing of the sensor.
Near-Field & Super-Resolution Sensors