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| Modern nano-materials and devices achieve their impressive performance by relying on clever design and a fine balance of micro- and nano-mechanical properties. Arguably, it is the mechanical properties that are the major single factor determining performance of any material or operation of a device. On the nanometre length scale, yet another very significant physical dimension comes into play - temporal (or “time domain”) behaviour of devices or materials. The examples of fast nanoscale physical phenomena range from magnetic or ferroelectric domains switching to lubrication in the hard drive, heat transfer in nanostructures, and functioning of MEMS (micro-electro-mechanical) and QEMS (quantum nano-electro-mechanical) systems. We in our group explore these fascinating features of nature around us (and inside us!), and related physical, chemical and biological phenomena and hope you will share with us the fascination of these discoveries. Oleg Kolosov Physics Department, Lancaster University, UK |
Subsurface and 3D imaging of nanostuctures
Exploring dynamic phenomena in SPM
The ultrasonic vibration that is used in Ultrasonic Force Microscopy (UFM) inevitably modulates the tip-surface interaction on ns time scale. If a physical action (second mechanical vibration, thermal expansion, electrical field, etc.) varies at the adjacent frequency, the SPM response varies at the difference frequency - a working principle for Heterodyne Force Microscopy, or HFM. HFM enables mapping dynamic physical properties in nano-systems with ns time sensitivity. These include transitions in ferroelectric and phase change materials, lubrication in hard drives, and nanoscale dynamic phenomena in MEMS and QEMS systems.
Functional nanomaterials
Functional materials that respond to the environment can be used as memory elements, "smart" self-healing materials, and "adaptive" materials for optimal energy storage . Building upon our initial exploration of ferroelectric domains switching using SPM, we are now exploring dynamics of switching phenomena in ferroelectrics, as well as in phase change materials (PCM, picture) - a new platform aiming to replace "flash memory" by providing faster switching time, lower energy consumption and better retention of information. We also study graphene nanostructures as paltform for effiicient rechargeable batteries and super-capacitors.
Combinatorial materials discovery
Using parallel high throughput synthesis and characterisation of materials allowed us to explore large "combinatorail space" of materials composition and to find the optimal recepies for polymers optimizing DNA separation, anti-fouling coating on sea ships and (picture) polymeric additives for delivery of whitening bioactives in the toothpaste.
Nanomechanics of materials and interfaces
A nanoscale junction between Scanning Probe Microscope (SPM) tip apex and the sample can serve as a nanoscale "mechanical diode" that detects HF ultrasonic vibration of few MHz to 100 MHz frequency in a same way as a diode detects HF electrical oscillations. The resulting approach - Ultrasonic Force Microscopy, or UFM, pioneered in our group, offers unique and unamiguous contrast to nanostructures ranging from semiconductor chips and graphene layers to polymers and peptide fibres (picture - topo and UFM images of SiC - Al2O3 ceramic composite).
Mapping thermal properties on nanoscale
Extreme density of power dissipation in modern electronics nanoscale devices needs suitable methods for exploring heat generation and management. We have developed a suite of Scanning Thermal Microscopy (SThM) based approaches using HV environment and novel probes and achieved spatial resolution to thermal conductibvity exeeding 50 nm. That allowed us to explore thermal transport in carbon nanotubes, graphene materials and other solid state devices (picture - SThM setup developed in our group for imaging graphene layers, in collaboration with M. Pumarol, Lancaster University, UK and M. Rosamond, M. Petty and D. Zeze, Durham University, UK).
Micromechanics of biomaterials
Micromechanical properties of biological tissues and cells play an essential role in normal functioning of organs and also can indicate an early stage of a desease. Using UFM in aqueous environment we explore area of extreme interest of early stages of Amyloid and Amyline fibres assembly, the peptides that are implicated in Alzheimer's decease and Type II diabetis. Another pilot project on micro-elastography targets direct 3D mapping of elastic of skin and cells using combination of optical detection by OM and Optical Coherence Tomography (OCT) and mechanical vibrations (picture - OCT image of human skin profile).
Microresonators - fluid sensors and quantum phenomena
Mechanical resonators - tuning forks are best known for their use in watches and frequncy control. We established their completely different ability to simultaneously measure several parameters of a surrounding liquid (namely, density, viscosity and dielectric constant). Our developments and these sensors (picture) are now used in the automotive industry to monitor engine oil quality and to indicate optimal oil change schedule, and in oil and gas exploration several thousands meters under the Earth's surface, as well as to detect quantum turbulence in He3 and He4 quantum liquids.
