Browsing by Author "Díaz Díaz, Diego Ignacio"
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- ItemAFM Study of Elastic Module of Physical-Vapor-Deposited Phospholipid Membranes(2018) Volkmann, Ulrich Georg; Catalán López, Rodrigo Esteban; Retamal Ponce, María José; Cisternas Fruns, Marcelo Andrés; Moraga Vent, Nicolás Andrés; Díaz Díaz, Diego Ignacio; Corrales, Tomás P.; Pérez-Acle, Tomás; Soto Arriaza, Marco Antonio; Huber, PatrickThe physical study of artificial phospholipid membranes on solid substrates has become a relevant way to gain insights into the physical behavior of cell membranes. The study of mechanical properties of artificial membranes (lab-made) has become possible with the use of atomic force microscopy. Here, we analyze the Young's modulus and adhesion force of several phospholipidic membranes as a function of temperature using Scanning Force Spectroscopy (SFS). Phospholipids were deposited onto double-polished silicon substrates by physical vapor deposition (PVD), as we have recently reported [1, 2]. We have used Raman spectroscopy to show that the chemical structure of our deposited phospholipid remains unaltered after PVD. After PVD we performed AFM and SFS measurements on the following phospholipids: DPPC, DMPC and DSPC. Measurements using AFM in liquid confirm the self-assembly of the phospholipid bilayer. By using SFS of the deposited membrane in liquid, we observe 2 phase transitions, both in Younǵs Modulus, as well as adhesion channels. The measured phase transitions are consistent with the ripple-gel transition and the gel-liquid crystalline phases. Furthermore, we have studied the frequency dependence of these phase transitions by changing the tip velocity in SFS experiments. Supported by FONDECYT grant # 1141105 (UGV), FONDECYT INICIACION grant # 11160664 (TPC), CONICYT Fellowships (RC and MC), Postdoctoral Fellowship FONDECYT 3160803 (MJR) and CONICYT-PIA ACT 1409. [1] María J. Retamal, Marcelo A. Cisternas, Sebastian E. Gutierrez-Maldonado, Tomas Perez-Acle, Birger Seifert, Mark Busch, Patrick Huber and Ulrich G. Volkmann, J. Chem. Phys. 141, 104201 (2014). [2] María Jose Retamal, Tomas P. Corrales, Marcelo A. Cisternas, Nicolas H. Moraga, Diego I. Diaz, Rodrigo E. Catalan, Birger Seifert, Patrick Huber, and Ulrich G. Volkmann. Biomacromolecules 17 (3), 1142 (2016).
- ItemWetting properties of n-alkane thin films to understand the adherence mechanism of artificial membranes on silicon substrates(2017) Díaz Díaz, Diego Ignacio; Volkmann, Ulrich; Pontificia Universidad Católica de Chile. Facultad de FísicaIn this work we present a study of the wetting properties of silicon samples coated with a single layer of n-alkane molecules that self-assemble perpendicular to the surface.The types of molecules studied here are n-alkane chains, mainly n-dotriacontane (n-C32 H66), that were deposited on silicon substrates with a thin native silicon oxidelayer (15˚A). The thin films were prepared by Dip-Coating technique in a C32 H66/n-heptane solution. The techniques used to characterize these films are Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). In this research a contact angle setup was developed to measure wettability of submonolayer films. An influence of morphology and coverage on the contact angle was found. Moreover, alkane molecules migrate much like a reverse coffee-ring effect after drop evaporation, forming complex tail-like morphologies.This research is relevant to understand alkane adhesion on silicon substrates, which is related with artificial membrane fabrication, which are used for biosensors applications. Micro-structured pattern like stripes could be applied as templates for other materials, especially considering the possibility of creating homogeneous surfaces with nanometer thick films.