NanoWorld Services (Germany)

In this paper, a relatively new hyper convolution spectra for characterization liquid, viscoelastic and solid samples is presented. Special attention is paid to the biophysical characterization of epithelial tissues and early detection of cancer of the skin, cervix, colon, and oral cavity. The method is based on the use of two types of white light, diffuse and polarized, from the same LED light sources. Based on the subtraction of the intensity values of these two lights and using the hyper convolution algorithm, the ratio of paired and unpaired electrons of tissue is obtained. This ratio correlates well with the state of the tissue: normal, irritating, precancerous, and cancerous. First, a proof-of-concept studies were performed, and later clinical studies on samples from one thousand two hundred fifteen people were performed. It showed that hyper Opto-Magnetic Imaging Spectroscopy (OMIS) can detect epithelial tissue cancers with an accuracy of 85-96%. Bearing in mind that the OMIS method also acquires the biophysical characteristics of the deeper skin layers (epidermis, basement membrane, dermis) by analysing convolution spectra of RGB channels of both diffuse and polarized white light, it is possible to apply this method in cosmetics (skin hydration, collagen, and elastin states, etc.). During OMIS applications, we noticed places where improvements could be made to increase method’s accuracy using advanced machine learning methodologies.

This work presents a novel approach for combined micro- and nanofabrication based on the local laser exposure of an UV-curing material through a structured mold. The proposed process makes use of the high freedom of design of direct laser writing (DLW) and the high resolution of soft lithography molds (made e.g. from PDMS). By optimizing the exposure process it was possible to fabricate locally defined hierarchical structures with a height of around 16 μm, that are fully covered with nanometer-sized holes using OrmoComp®. Manual test imprints showed that the fabricated structures can be used for “step and repeat” nanoimprint processes. Furthermore, the local transfer of nanostructures into two different soft lithography resists (Katiobond 110707, mr-NIL210) was investigated. Diffusion of resist components into the PDMS mold was observed and could be prohibited by the use of hybrid molds, which employ OrmoComp® as structure containing layer. First experiments revealed successful transfer of the mold’s nanostructures into mr-NIL210 but still leave room for improvement concerning the process parameters.

Using conductive atomic force microscopy (cAFM), I-V characteristics on dot-like areas can be acquired to study current conduction mechanisms or dielectric breakdown statistics on the nanoscale. However, today such I-V measurements exhibit relatively low sensitivity. It is shown that parasitic capacitances Cpar in the pF range resulting from the cantilever of the probe and the probe holder limit the sensitivity of cAFM. This is proven by the evaluation of different voltage sweep rates sr and the analysis of the influence of measurement position on the sample for both, commercially available probes as well as shielded coplanar probes prepared by focused ion beam. Compared to standard probes, shielded probes show decreased displacement currents and nearly negligible transient effects for the I-V characteristics even at high sweep rates up to 10 V/s. In addition, the influence of the measurement position is much less pronounced for the shielded probes. This means, the increase of Cpar (including the probe holder) when measuring in the center of a large sample compared to measuring at the edge of the sample is around 45% for the shielded probes compared to nearly 85% for standard probes. Here, a simple data evaluation procedure is proposed to correct the measured data for the displacement current, which will strongly improve the effective sensitivity of cAFM especially for high sr, which are preferred to decrease electrical stress during the measurement. However, for higher sr, noise increases and must be reduced in future cAFM systems by additional measures.

The effective Q-factor of the cantilever is one of the most important figures-of-merit for a non-contact atomic force microscope (NC-AFM) operated in ultra-high vacuum (UHV). We provide a comprehensive discussion of all effects influencing the Q-factor and compare measured Q-factors to results from simulations based on the dimensions of the cantilevers. We introduce a methodology to investigate in detail how the effective Q-factor depends on the fixation technique of the cantilever. Fixation loss is identified as a most important contribution in addition to the hitherto discussed effects and we describe a strategy for avoiding fixation loss and obtaining high effective Q-factors in the force microscope. We demonstrate for room temperature operation, that an optimum fixation yields an effective Q-factor for the NC-AFM measurement in UHV that is equal to the intrinsic value of the cantilever.