Staff member

Jordi Otero Díaz

Postdoctoral Researcher
Cellular and Respiratory Biomechanics
+34 934 031 184
Staff member publications

Botaya, L., Coromina, X., Samitier, J., Puig-Vidal, M., Otero, J., (2016). Visualized multiprobe electrical impedance measurements with STM tips using shear force feedback control Sensors 16, (6), 757

Here we devise a multiprobe electrical measurement system based on quartz tuning forks (QTFs) and metallic tips capable of having full 3D control over the position of the probes. The system is based on the use of bent tungsten tips that are placed in mechanical contact (glue-free solution) with a QTF sensor. Shear forces acting in the probe are measured to control the tip-sample distance in the Z direction. Moreover, the tilting of the tip allows the visualization of the experiment under the optical microscope, allowing the coordination of the probes in X and Y directions. Meanwhile, the metallic tips are connected to a current-voltage amplifier circuit to measure the currents and thus the impedance of the studied samples. We discuss here the different aspects that must be addressed when conducting these multiprobe experiments, such as the amplitude of oscillation, shear force distance control, and wire tilting. Different results obtained in the measurement of calibration samples and microparticles are presented. They demonstrate the feasibility of the system to measure the impedance of the samples with a full 3D control on the position of the nanotips.

Keywords: Impedance measurement, Multiprobe SPM, Quartz tuning forks, Scanning probe microscopy, Scanning tunneling microscope (STM) tip

González, L., Otero, J., Agusil, J. P., Samitier, J., Adan, J., Mitjans, F., Puig-Vidal, M., (2014). Micropattern of antibodies imaged by shear force microscopy: Comparison between classical and jumping modes Ultramicroscopy 136, 176-184

Quartz tuning fork devices are increasingly being used as nanosensors in Scanning Probe Microscopy. They offer some benefits with respect to standard microfabricated cantilevers in certain experimental setups including the study of biomolecules under physiological conditions. In this work, we compare three different working modes for imaging micropatterned antibodies with quartz tuning fork sensors: apart from the classical amplitude and frequency modulation strategies, for first time the jumping mode is implemented using tuning forks. Our results show that the molecules suffer less degradation when working in the jumping mode, due to the reduction of the interaction forces.

Birhane, Y., Otero, J., Pérez-Murano, F., Fumagalli, L., Gomila, G., Bausells, J., (2014). Batch fabrication of insulated conductive scanning probe microscopy probes with reduced capacitive coupling Microelectronic Engineering 119, 44-47

We report a novel fabrication process for the batch fabrication of insulated conductive scanning probe microscopy (SPM) probes for electrical and topographic characterization of soft samples in liquid media at the nanoscale. The whole SPM probe structure is insulated with a dielectric material except at the very tip end and at the contact pad area to minimize the leakage current in liquid. Additionally, the geometry of the conducting layer in the probe cantilever and substrate is engineered to reduce the parasitic capacitance coupling with the sample. The electrical characterization of the probes has shown that parasitic capacitances are significantly reduced as compared to fully metallized cantilevers.

Keywords: Conductive scanning probe microscopy (C-SPM), EFM, SECM, SECM-AFM, SIM

Otero, J., Baños, R., González, L., Torrents, E., Juárez, A., Puig-Vidal, M., (2013). Quartz tuning fork studies on the surface properties of Pseudomonas aeruginosa during early stages of biofilm formation Colloids and Surfaces B: Biointerfaces 102, 117-123

Scanning probe microscopy techniques are powerful tools for studying the nanoscale surface properties of biofilms, such as their morphology and mechanical behavior. Typically, these studies are conducted using atomic force microscopy probes, which are force nanosensors based on microfabricated cantilevers. In recent years, quartz tuning fork (QTF) probes have been used in morphological studies due to their better performance in certain experiments with respect to standard AFM probes. In the present work QTF probes were used to measure not only the morphology but also the nanomechanical properties of Pseudomonas aeruginosa during early stages of biofilm formation. Changes in bacterium size and the membrane spring constant were determined in biofilms grown for 20, 24 and 28. h on gold with and without glucose in the culture media. The results obtained using the standard AFM and QTF probes were compared. Both probes showed that the bacteria forming the biofilm increased in size over time, but that there was no dependence on the presence of glucose in the culture media. On the other hand, the spring constant increased over time and there was a clear difference between biofilms grown with and without glucose. This is the first time that QTF probes have been used to measure the nanomechanical properties of microbial cell surfaces and the results obtained highlight their potential for studying biological samples beyond topographic measurements.

Otero, J., Puig-Vidal, M., Frigola, M., Casals, A., (2009). Micro-to-nano optical resolution in a multirobot nanobiocharacterization station 2009 IEEE/RSJ International Conference on Intelligent Robots and Systems, IROS 2009 IEEE RSJ International Conference on Intelligent Robots and Systems , IEEE (St. Louis, USA) , 5357-5362

A multi-robot cooperation station for nano-bio characterization of biological specimens is presented. The station is composed of two long travel range and high resolution robots equipped with self-sensing nanoprobes that are able to cooperate with each other and with standard AFM systems, over a common sample. The robots are guided by the use of an upright high-depth-of-field optical microscope to perform complex nano-bio characterization experiments. To achieve the required precision between the two robots reference frames, specific image processing techniques are needed. One of the tips is dedicated to acquire the topography of the sample at nano scale while the second probe performs the biocharacterization experiments. The obtained results show that the two robots can cooperate within the required resolution in bacterial nanomechanical characterization while high resolution topographic images are acquired.

Keywords: AFM

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