The FluidFM enables the immobilization of single cells on a hollow cantilever using relative underpressure. In this study, we systematically optimize versatile measurement parameters (setpoint, z-speed, z-length, pause time, and relative underpressure) to improve the quality of force-distance curves recorded with a FluidFM. Using single bacterial cells (here the gram negative seawater bacterium Paracoccus seriniphilus and the gram positive bacterium Lactococcus lactis), we show that Single Cell Force Spectroscopy experiments with the FluidFM lead to comparable results to a conventional Single Cell Force Spectroscopy approach using polydopamine for chemical fixation of a bacterial cell on a tipless cantilever. Even for the bacterium Lactococcus lactis, which is difficult to immobilze chemically (like seen in an earlier study), immobilization and the measurement of force-distance curves are possible by using the FluidFM technology.

Two-photon laser lithography has become one of the most promising additive manufacturing techniques on the micron scale and is applied, e.g., in fields of micro-optics and -robotics as well as optical and mechanical metamaterials. Here, we report on the feasibility, limits and general benefits of this method to fabricate material measures for the calibration of industrial optical topography measuring devices. Since calibration procedures are essential in the scientific and industrial application of those measuring instruments, appropriate material measures are highly required. In contrast to traditional manufacturing technologies, we show that two-photon laser lithography allows a highly resolved fabrication of multiple, almost arbitrary standardized calibration geometries on a micron length scale. Hereby, all structures are fabricated on only one single substrate, therefore enabling a mapping of a broad range of metrological characteristics for topography characterization. The most required calibration geometries are manufactured and analyzed regarding their aging behavior, their quality improvement by a post-UV development and the resolution limits within the manufacturing as well as the calibration process. Thus, the general industrial and scientific relevance of manufacturing material measures with two-photon laser lithography is demonstrated.

Force spectroscopy and especially single cell force spectroscopy with bacterial probes provide a powerful tool for the investigation of bacterial adhesion to different surfaces. Thereby, a crucial step is the immobilization of the bacteria on the cantilever. Until today, there have been developed versatile methods to attach bacteria to a cantilever, but only few studies compare these methods in a quantitative way. In this work, different functionalizations of the cantilever as well as two picking-up parameters for three gram-positive bacteria are evaluated. While there is no functionalization which works best for all of the bacteria, polydopamine, the adhesive protein Cell-Tak TM and a gas phase silanization in combination with an activation of the bacteria are the most promising candidates. Further, some general trends how the two investigated picking-up parameters influence the adhesive behavior of the bacteria on the cantilever, which also depends strongly on the shape of the bacteria are presented.

The FluidFM enables the immobilization of single cells on a hollow cantilever using relative underpressure. In this study, we systematically optimize versatile measurement parameters to improve the quality of force-distance curves recorded with a FluidFM. Using single bacterial cells, we show that Single Cell Force Spectroscopy experiments with the FluidFM lead to comparable results to a conventional Single Cell Force Spectroscopy approach using polydopamine for chemical fixation of a bacterial cell.