Gabriel Gomila

Universitat de Barcelona, Electronics, Faculty Member

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Martí Checa

Universitat de Barcelona

University of Mumbai

The University of Manchester

Enrico Brinciotti

Keysight Technologies

Gabriel Gomila

Bernardo Ruegger Almeida Neves

Univerdade Federal de Minas Gerais

Wagner Rodrigues

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Papers by Gabriel Gomila

Fast Label‐Free Nanoscale Composition Mapping of Eukaryotic Cells Via Scanning Dielectric Force Volume Microscopy and Machine Learning

Small Methods

The ORCID identification number(s) for the author(s) of this article can be found under https://d... more

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Depth mapping of metallic nanowire polymer nanocomposites by scanning dielectric microscopy

Nanoscale, 2021

The depth mapping of metallic nanowires buried in polymer nanocomposites can be achieved in a non... more

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Dielectric Imaging of Fixed HeLa Cells by In-Liquid Scanning Dielectric Force Volume Microscopy

Nanomaterials, 2021

Mapping the dielectric properties of cells with nanoscale spatial resolution can be an important ... more Mapping the dielectric properties of cells with nanoscale spatial resolution can be an important tool in nanomedicine and nanotoxicity analysis, which can complement structural and mechanical nanoscale measurements. Recently we have shown that dielectric constant maps can be obtained on dried fixed cells in air environment by means of scanning dielectric force volume microscopy. Here, we demonstrate that such measurements can also be performed in the much more challenging case of fixed cells in liquid environment. Performing the measurements in liquid media contributes to preserve better the structure of the fixed cells, while also enabling accessing the local dielectric properties under fully hydrated conditions. The results shown in this work pave the way to address the nanoscale dielectric imaging of living cells, for which still further developments are required, as discussed here.

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Electrical Properties of Outer Membrane Extensions from Shewanella Oneidensis MR-1

Nanoscale, 2021

Shewanella oneidensis MR-1 are metal-reducing bacterial cells able to exchange electrons with sol... more

Dielectric nanotomography based on electrostatic force microscopy: A numerical analysis

Journal of Applied Physics, 2020

Electrostatic force microscopy (EFM) can image nanoscale objects buried below the surface. Here, ... more Electrostatic force microscopy (EFM) can image nanoscale objects buried below the surface. Here, we theoretically show that this capability can be used to obtain nanotomographic information, i.e., the physical dimensions and dielectric properties, of buried nano-objects. These results constitute a first step toward implementing a nondestructive dielectric nanotomography technique based on EFM with applications in materials sciences and life sciences.Electrostatic force microscopy (EFM) can image nanoscale objects buried below the surface. Here, we theoretically show that this capability can be used to obtain nanotomographic information, i.e., the physical dimensions and dielectric properties, of buried nano-objects. These results constitute a first step toward implementing a nondestructive dielectric nanotomography technique based on EFM with applications in materials sciences and life sciences.

Mapping the dielectric constant of a single bacterial cell at the nanoscale with scanning dielectric force volume microscopy

Nanoscale, 2019

A method to map the dielectric constant of non-planar samples is presented, and applied to single... more

Sizing single nanoscale objects from polarization forces

Scientific Reports, 2019

Sizing natural or engineered single nanoscale objects is fundamental in many areas of science and... more Sizing natural or engineered single nanoscale objects is fundamental in many areas of science and technology. To achieve it several advanced microscopic techniques have been developed, mostly based on electron and scanning probe microscopies. Still for soft and poorly adhered samples the existing techniques face important challenges. Here, we propose an alternative method to size single nanoscale objects based on the measurement of its electric polarization. The method is based on Electrostatic Force Microscopy measurements combined with a specifically designed multiparameter quantification algorithm, which gives the physical dimensions (height and width) of the nanoscale object. The proposed method is validated with ~50 nm diameter silver nanowires, and successfully applied to ~10 nm diameter bacterial polar flagella, an example of soft and poorly adhered nanoscale object. We show that an accuracy comparable to AFM topographic imaging can be achieved. The main advantage of the prop...

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Interdigitation in spin-coated lipid layers in air

Colloids and Surfaces B: Biointerfaces, 2018

In this study, we show that dry saturated phospholipid layers prepared by the spin-coating techni... more In this study, we show that dry saturated phospholipid layers prepared by the spin-coating technique could present thinner regions associated to interdigitated phases under some conditions. The morphological characteristics of lipid layers of saturated phosphocholines, such as dilauroylphosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC), have been measured by Atomic Force Microscopy and revealed that the presence of interdigitated regions is not induced by the same parameters that induce them in hydrated samples. To achieve these results the effect of the lipid hidrocabonated chain length, the presence of alcohol in the coating solution, the spinning velocity and the presence of cholesterol were tested. We showed that DPPC and DSPC bilayers, on the one side, can show structures with similar height than interdigitated regions observed in hydrated samples, while, on the other side, DLPC and DMPC tend to show no evidence of interdigitation. Results indicate that the presence of interdigitated areas is due to the presence of lateral tensions and, hence, that they can be eliminated by releasing these tensions by, for instance, the addition of cholesterol. These results demonstrate that interdigitation in lipid layers is a rather general phenomena and can be observed in lipid bilayers in dry conditions.

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Nanoscale dielectric microscopy of non-planar samples by lift-mode electrostatic force microscopy

Nanotechnology, 2016

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Internal Hydration Properties of Single Bacterial Endospores Probed by Electrostatic Force Microscopy

ACS Nano, 2016

We show that the internal hydration properties of single Bacillus cereus endospores in air under ... more We show that the internal hydration properties of single Bacillus cereus endospores in air under different relative humidity (RH) conditions can be determined through the measurement of its electric permittivity by means of quantitative electrostatic force microscopy (EFM). We show that an increase in the RH from 0% to 80% induces a large increase in the equivalent homogeneous relative electric permittivity of the bacterial endospores, from ~4 up to ~17, accompanied only by a small increase in the endospore height, of just a few nanometers. These results correlate the increase of the moisture content of the endospore with the corresponding increase of environmental RH. 3D finite element numerical calculations, which include the internal structure of the endospores, indicate that the moisture is mainly accumulated in the external layers of the endospore, hence preserving the core of the endospore at low hydration levels. This mechanism is different from what we observe for vegetative bacterial cells of the same species, in which the cell wall at high humid atmospheric conditions is not able to preserve the cytoplasmic region at low hydration levels. These results show the potential of quantitative EFM under environmental humidity control to study the hygroscopic properties of small scale biological (and non-biological) entities and to determine its internal hydration state. A better understanding of nano-hygroscopic properties can be of relevance in the study of essential biological processes and in the design of bio-nanotechnological applications.

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Quartz tuning fork-based conductive atomic force microscope with glue-free solid metallic tips

Sensors and Actuators A: Physical, 2015

ABSTRACT Here we devise a conductive Atomic Force Microscope (C-AFM) based on quartz tuning forks... more ABSTRACT Here we devise a conductive Atomic Force Microscope (C-AFM) based on quartz tuning forks (QTFs) and metallic tips capable of simultaneously imaging the topography and conductance of a sample with nanoscale spatial resolution. The system is based on a header design which allows the metallic tip to be placed in tight and stable mechanical contact with the QTF without the need to use any glue. This allows electrical measurements to be taken with an electrically excited QTF with the two prongs free. The amplitude oscillation of the QTF is used to control the tip–sample distance and to acquire the topographic images. Meanwhile, the metallic tip is connected to a current–voltage amplifier circuit to measure the tip–sample field emission/tunnelling current and to produce the conductive images. This method allows decoupled electrical measurement of the topography and electrical properties of the sample. The results we obtain from calibration samples demonstrate the feasibility of this measurement method and the adequacy of the performance of the system.

Artificial nose integrating biological olfactory receptors and NEMS

Modelization of thermal fluctuations in G protein-coupled receptors

AIP Conference Proceedings, 2005

We simulate the electrical properties of a device realized by a G protein coupled receptor (GPCR)... more We simulate the electrical properties of a device realized by a G protein coupled receptor (GPCR), embedded in its membrane and in contact with two metallic electrodes through which an external voltage is applied. To this purpose, recently, we have proposed a model based on a coarse graining description, which describes the protein as a network of elementary impedances. The network is built from the knowledge of the positions of the C α atoms of the amino acids, which represent the nodes of the network. Since the elementary impedances are taken depending of the inter-nodes distance, the conformational change of the receptor induced by the capture of the ligand results in a variation of the network impedance. On the other hand, the fluctuations of the atomic positions due to thermal motion imply an impedance noise, whose level is crucial to the purpose of an electrical detection of the ligand capture by the GPCR. Here, in particular, we address this issue by presenting a computational study of the impedance noise due to thermal fluctuations of the atomic positions within a rhodopsin molecule. In our model, the C α atoms are treated as independent, isotropic, harmonic oscillators, with amplitude depending on the temperature and on the position within the protein (α-helix or loop). The relative fluctuation of the impedance is then calculated for different temperatures.

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Nanoscale electrical conductivity of the purple membrane monolayer

Physical Review E, 2007

Nanoscale electron transport through the purple membrane monolayer, a two-dimensional crystal lat... more Nanoscale electron transport through the purple membrane monolayer, a two-dimensional crystal lattice of the transmembrane protein bacteriorhodopsin, is studied by conductive atomic force microscopy. We demonstrate that the purple membrane exhibits nonresonant tunneling transport, with two characteristic tunneling regimes depending on the applied voltage ͑direct and Fowler-Nordheim͒. Our results show that the purple membrane can carry significant current density at the nanometer scale, several orders of magnitude larger than previously estimated by macroscale measurements.

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Quantification of the dielectric constant of single non-spherical nanoparticles from polarization forces: eccentricity effects

Nanotechnology, 2013

We analyze by means of finite-element numerical calculations the polarization force between a sha... more We analyze by means of finite-element numerical calculations the polarization force between a sharp conducting tip and a non-spherical uncharged dielectric nanoparticle with the objective of quantifying its dielectric constant from electrostatic force microscopy (EFM) measurements. We show that for an oblate spheroid nanoparticle of given height the strength of the polarization force acting on the tip depends linearly on the eccentricity, e, of the nanoparticle in the small eccentricity and low dielectric constant regimes (1 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; e &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 2 and 1 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; ε(r) &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 10), while for higher eccentricities (e &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 2) the dependence is sub-linear and finally becomes independent of e for very large eccentricities (e &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30). These results imply that a precise account of the nanoparticle shape is required to quantify EFM data and obtain the dielectric constants of non-spherical dielectric nanoparticles. Experimental results obtained on polystyrene, silicon dioxide and aluminum oxide nanoparticles and on single viruses are used to illustrate the main findings.

High-speed counting and sizing of cells in an impedance flow microcytometer with compact electronic instrumentation

Microfluidics and Nanofluidics, 2013

Here we describe a high-throughput impedance flow cytometer on a chip. This device was built usin... more Here we describe a high-throughput impedance flow cytometer on a chip. This device was built using compact and inexpensive electronic instrumentation. The system was used to count and size a mixed cell sample containing red blood cells and white blood cells. It demonstrated a counting capacity of up to *500 counts/s and was validated through a synchronised high-speed optical detection system. In addition, the device showed excellent discrimination performance under high-throughput conditions. Keywords Microcytometry Á Microfluidics Á Impedance Á Electronics Á Red blood cells (RBCs) Á White blood cells (WBCs)

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Nanoscale capacitance microscopy of thin dielectric films

Journal of Applied Physics, 2008

We present an analytical model to interpret nanoscale capacitance microscopy measurements on thin... more We present an analytical model to interpret nanoscale capacitance microscopy measurements on thin dielectric films. The model displays a logarithmic dependence on the tip-sample distance and on the film thickness-dielectric constant ratio and shows an excellent agreement with finite-element numerical simulations and experimental results on a broad range of values. Based on these results, we discuss the capabilities of nanoscale capacitance microscopy for the quantitative extraction of the dielectric constant and the thickness of thin dielectric films at the nanoscale.

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Nanoscale Measurement of the Dielectric Constant of Supported Lipid Bilayers in Aqueous Solutions with Electrostatic Force Microscopy

Biophysical Journal, 2013

We present what is, to our knowledge, the first experimental demonstration of dielectric constant... more We present what is, to our knowledge, the first experimental demonstration of dielectric constant measurement and quantification of supported lipid bilayers in electrolyte solutions with nanoscale spatial resolution. The dielectric constant was quantitatively reconstructed with finite element calculations by combining thickness information and local polarization forces which were measured using an electrostatic force microscope adapted to work in a liquid environment. Measurements of submicrometric dipalmitoylphosphatidylcholine lipid bilayer patches gave dielectric constants of ε r~3 , which are higher than the values typically reported for the hydrophobic part of lipid membranes (ε r~2) and suggest a large contribution of the polar headgroup region to the dielectric response of the lipid bilayer. This work opens apparently new possibilities in the study of biomembrane electrostatics and other bioelectric phenomena.

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Nondestructive thickness measurement of biological layers at the nanoscale by simultaneous topography and capacitance imaging

Applied Physics Letters, 2007

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Dynamic electrostatic force microscopy in liquid media

Applied Physics Letters, 2012

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Fast Label‐Free Nanoscale Composition Mapping of Eukaryotic Cells Via Scanning Dielectric Force Volume Microscopy and Machine Learning

Small Methods

The ORCID identification number(s) for the author(s) of this article can be found under https://d... more

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Depth mapping of metallic nanowire polymer nanocomposites by scanning dielectric microscopy

Nanoscale, 2021

The depth mapping of metallic nanowires buried in polymer nanocomposites can be achieved in a non... more

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Dielectric Imaging of Fixed HeLa Cells by In-Liquid Scanning Dielectric Force Volume Microscopy

Nanomaterials, 2021

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Electrical Properties of Outer Membrane Extensions from Shewanella Oneidensis MR-1

Nanoscale, 2021

Shewanella oneidensis MR-1 are metal-reducing bacterial cells able to exchange electrons with sol... more

Dielectric nanotomography based on electrostatic force microscopy: A numerical analysis