Technology >> Electrospray Deposition Method Principles The Electrospray Deposition Method is a process by means of which a liquid is transformed into a fine mist. This transformation is brought about by the application of a very high voltage electric field to the capillary through which the liquid passes. In recent years, this methodology is widely used as an ionizer for mass spectrometers. The Electrospray Deposition Method (ESD method) is the technique of spraying various kinds of solution of biomacromolecules and/or synthetic polymers, to make them form nano-sized particles and fibers (nano-fiber), and to let them accumulate and adhere on a substrate using electrostatic force. While electrospray is a very complicated physical process, which is not fully understood, generally what happens is as follows. When a sample liquid stored in a thin capillary is supplied with several thousands volts relative to counter electrode, a strong electric field is generated at the tip of the capillary, due tos the effect of electric field concentration. As the liquid begins to exit from the capillary, it forms a conical shape with the electrically charged ions gathered on its surface. (This is called Taylor cone). Subsequently, when the electrostatic force becomes stronger than surface tension, the liquid erupts from the tip of the capillary to form a fine jet. Since the jet is highly charged, the liquid immediately turns into fine droplets to generate spray with each droplet spilt from the next by electrostatic force. (This is called the Coulomb Explosion). The droplets formed by means of electrospray are tiny. Therefore, the solvent evaporates and dries in a very short period of time, and as a consequence, it forms very fine nano-particles. These charged tiny particles are attracted to the counter-electrode by electrostatic force, and are deposited in various patterns, which can be controlled by mask(s) made of insulating material and/or additional electrode(s). Electrospray Deposition An atomic force microscope image of thin film with an electrospray-deposit Features The Electrospray Deposition Method can: spray and deposit various substances such as organic/inorganic compounds, biomacromolecules and/or synthetic polymers. maintain the sample relatively free from damage, since the whole procedure is conducted under a room temperature and atmospheric pressure. create nano-sized particles and fibers. control depositions and patterns of the particle using electrostatic force. form the deposition in a larger area with a batch processing system. Applications Nano-fiber For manufacture of synthetic fiber, the mainstream technique used is to squeeze out synthetic polymers under compression through fine nozzles. However, D. H. Reneker et al. reported the possibility of forming fibers using the process now known as electrospinning. This is a technique by which a high voltage is applied to the nozzle and a liquid solution is sprayed forming nano-scaled fiber materials (3,4). The Esprayer, is capable of producing nano-metered levels of fibers (nano-fibers) by means of ESD method. Currently, with our Esprayers, wide ranging research and development is being carried out to fabricate nano-fibers from synthetic polymers and/or biomacromolecules(5,6). The nano-fibers fabricated by the ESD method can be used as catalytic carriers as well as high-performance membranes. They are not limited to high-performance filters and non-woven fabrics. A wide variety of usages are being investigated, not only for textile fabrics but also for electronic parts and high-performance batteries as well as for the materials used for biological research and medical treatment. Polyethylene Oxide Nanofiber from Dr. Tanioka, Tokyo Institute of Technology Related products: E-Sprayer™ Multi ES-2000 Series Nano-coating/Patterning The particles of materials fabricated by the ESD method can be reduced in diameter by less than dozens of nano-meters. Using this technique, various types of coating are practicable, with the materials like synthetic polymers and biomacromolecules such as proteins. Thickness of the coating is controllable at the level of nano-meters, and with the electrostatic force, it is theoretically possible to coat the substrate both of flat surface or of complex shapes. By using a mask of insulating material in the ESD method, electrostatic force controls the pattern of deposition and forms it in desired shape, either spotted or striped. The resolution of the deposit ranges from micron-scale to sub-micron-scale. Using this patterning ability, spot forming on protein chips and patterning as a scaffold of cell culturing can be carried out. An AFM image for electrospray-deposited nano-structure of alpha-lactalbumin Electrospray-deposited protein spots from Dr. Tanioka, Tokyo Institute of Technology from Dr. Nagamune, Tokyo University Related products: Esprayer™ Multi ES-2000 Series Esprayer™ Arrayer ES-3000 Series MC Film With the use of ESD method, freestanding protein films can be created (7). After treated the electrospray-deposited protein film with cross-linking reagents and separated from the substrate, a freestanding protein film (MC film) is formed approximately 700µm x 300µm and with a thickness of 1 to 2µm. Since the film is structured to be freestanding, it is possible to measure its mechanical properties and to detect a chemical interaction as a parameter change of the mechanical property (mechano-chemical method, MC method). This is a unique method of creating freestanding thin films from biological macromolecules, and therefore, it is a unique application of the ESD method. Such thin films can also be effective in evaluating photochemical properties (8), and considered valuable materials for filtration. Electrospray-deposited protein film for MC method Related products: MC apparatus Protein Chips ESD method is broadly applicable to the creation of biochips, including that of protein chips. In this field, the methodologies such as the spotting method, the ink-jet method, and the micro contact printing method have already been developed and employed. However, the ESD method provides higher resolution and greater use in mass chip fabrication with a batch process. In the field of protein chips, the ESD overcomes technical limitations in conventional methods and meets various laboratory needs. As an example of the protein chip created by ESD method, an analytical chip using antibodies is shown in the Figure below. It shows the results of a specific binding ability test verified by electrospray-deposited anti-IgGs of different mammals on a ITO-coating glass substrate by means of the ESD method, and then by reacting with different secondary antibodies. From these results, it is shown that the antibody-chip created by ESD method preserves the ability of specific binding, and neither cross-reactions nor non-specific bindings are observed. A detecting sensitivity of the chip was as low as 10 to 100pg/mL, which is considered to be a useful level of sensitivity. Immune-assay for electrospray-deposited IgG from different species from Dr. Nagamune, Tokyo University Related products: Esprayer™ Arrayer ES-3000 Series Microfluidic chip References Morozov, V. N. & Morozova, T. Y. Electrospray deposition as amethod to fabricate functionally active protein films. Anal.Chem..71, 1415-1420 (1999). Morozov, V. N. & Morozova, T. Y. Electrospray deposition as a method for mass fabrication of mono- and multicomponent microarrays of biological and biologically active substances. Anal. Chem. 71, 3110-3117 (1999). Doshi, J. & Reneker, D. H. J. Electrost. 35, 151-160 (1995). Reneker, D. H. & Chun, I. Nanotechnology 7, 216-223 (1996). Uematsu, I., Matsumoto, H., Morota, K., Minagawa, M., Tanioka, K., Yamagata, Y. & Inoue, K. Surface morphology and biological activity of protein thin films produced by electrospray deposition, J. Colloid Interface Sci., 269 336-340 (2004). Bumhwan, L., Kamiya, N., Machida, S., Yamagata, Y., Horie, K., & Nagamune, T. Fabrication of a protein film by electrospray deposition method and investigation of photochemical properties by persistent spectral hole burning. Biomaterials, 24, 2045-2051 (2003). Lee, B., Kim, J., Ishimoto, K., Yamagata, Y., Tanioka, A. & Nagamune, T. Fabrication of protein microarrays for immunoassay using the electrospray deposition (ESD) method. J. Chem. Eng. Jpn., 36, 1370-1375 (2003). Avseenko, N. V., Morozova, T. Y,. Ataullakhanov, F. I. & Morozov, V. N. Immobilization of proteins in immunochemical microarrays fabricated by electrospray deposition. Anal. Chem. 73, 6047-6052 (2001). Avseenko, N. V., Morozova, T. Y., Ataullakhanov, F. I. & Morozov, V. N. Immunoassay with multicomponent protein microarrays fabricated by electrospray deposition. Anal. Chem. 74, 927-933 (2002). Copyright (C) 2005 Fuence co., Ltd. All Rights Reseved.