Atomic Force Microscope (AFM)

Tampere University Foundation sr (Tampere University) executed a direct procurement of an atomic force microscope (AFM) for applications such as (but not limited to): (i) study of surface topography and mechanical modulus of light-and heat-sensitive thin films under photoirradiation and at different temperatures; (ii) imaging of live cells and mechanical mapping of extremely soft hydrogels; (iii) study of electronic properties (e.g. work function) and their degradation (e.g. under light irradiation) of organic and inorganic semiconducting materials. The system is installed in the Tampere Microscopy Center which has a broad userbase barring the acquisition of prototype systems.

The Atomic Force Microscope is installed in a microscopy center environment and was required to be a flexible system suited for analysis of varied samples including, but not limited to, metals, semiconductors, glasses, geological samples, polymers, fragile biological samples, and samples in liquids. One of the key research areas at Tampere University is photonics. Research on e.g. light-activated polymers and solar cells mandates that the acquired AFM has well established capability to measure with simultaneous illumination of the sample with varying light sources. The system needs to include optics for bottom illumination of samples. Another key application is quantitative mechanical mapping of varying samples ranging from hard materials to soft samples such as hydrogels and polymers. The system performance and automation over a wide range of measurement temperatures, and thus accounting for potential thermal expansion of the sample, is essential. This is essential also for measurements of photoactivated materials as well as performing photoconductive AFM measurements. For this, using a non-resonant, oscillating tip mode that does not require tuning of the cantilever resonance provides ease of use both in air and in liquid, under illumination and over various temperatures, which usually shift the cantilever resonance frequency. Because of the reasons above, true tip-scanning configuration was preferred. This means that the tip is actuated in all axes for the scanning motion, i.e., the scanner is not split into tip-Z, sample-XY motions. Scanner for all 3 axes forms single unit, which actuates the tip while maintaining sample-independent performance. In order to facilitate accurate imaging of delicate biological samples at the molecular level, imaging mode at a conventional imaging AFM speed (e.g. 512 pixels/line in 1s) that allows direct control of the tip-surface interaction force through force-distance spectroscopy and control of the peak force, was required. Mechanical properties including adhesion, modulus and dissipation were also acquired and displayed simultaneously to topography. The combination of requirements described above were fulfilled exclusively by the Dimension Icon Atomic Force Microscope from Bruker Nano Surfaces Division. Furthermore, only Bruker offered the oscillating tip mode mentioned above, with its patented PeakForce Tapping (PFT) mode (patent EP1938040A2 in the EU). PFT allows for a) non-resonant imaging in liquids and b) direct force control of the tip-surface interaction.