Electrospray

....Electrospray or Electrohydrodynamic spraying (EHDS), is a facile method that uses electrostatic fields for dispersing liquids as chargued micro- and nano- sized droplets with near size monodispersity. .

 

Numerical simulation of electrostatic sprays

Physical systems comprised of large numbers mutually interacting components, such as electrosprays, which comprise many thousands of electrostatically interacting droplets, are difficult to simulate. For N droplets, about N2 interactions must be computed at each time step. We have developed codes that can carry out these computations very fast without loss of predictive power. Recently, we have recently used such strategies for simulating evaporating electrosprays.

 

....Snapshot of droplet positions of an electrospray characterized by non-volatile droplets in a lognormal size distribution with d10 = 8.8 um and CV=20%.

....Droplets are injected at the top of the spray plume, and move downward toward a collector plate at z=0.03 m

...Left panel- Snapshot of evaporating methanol electrospray droplets (initial d10 = 8 μm) and induced air flow streamlines. ...Right panel- Rate of generation of charge at a threshold droplet diameter of d* = 1 μm, showing fringes of intense Rayleigh-Coulomb explosion events.

 

Multiplexing of electrospray systems

Scaling up from a single electrospray emitter to a matrix of emitters is challenging because electrostatic shielding between the emitters debilitates the electric field. We are studying the conditions leading to stable electrospraying from linear arrays of cylindrical emitters. Such arrays can be used for making droplets, nanoparticles, coatings, or printed patterns.

 

Array of 5 emitters

Collected spots of polymer microparticles

 

A preliminary report of this research was presented at the 2014 International Aerosol Conference in Busan, Korea.

 

Electrospray deposition and printing: Granular films

Film of ethyl cellulose particles ~1 um size

...When polymer solutions are electrosprayed toward a plate, granular films are collected if the droplets dry up before depositing. Often, these films accumulate enough electrostatic charge to cause big changes in the spray particle/droplet trajectories. Interestingly, through this process, the porosity of the film remains constant in time.

 

Publications

Grifoll, J., Rosell-Llompart, J. (2014). Continuous droplets charge method for the Lagrangian simulation of electrostatic sprays.Journal of Electrostatics, 72(5),357-364; doi: 10.1016/j.elstat.2014.06.011 .

Arumugham-Achari, A.K, Grifoll, J., Rosell-Llompart, J. (2013). Two-way coupled numerical simulation of electrospray with induced gas flow, Journal of Aerosol Science. 65,121-133; doi:10.1016/j.jaerosci.2013.07.005.

Bodnár, E., Rosell-Llompart, J.( 2013). Growth Dynamics of Granular Films Produced by Electrospray , Journal of Colloid and Interface Science, 407, 536-545 .

Grifoll J, Rosell-Llompart, J. (2012). Efficient Lagrangian simulation of electrospray droplets dynamics.Journal of Aerosol Science. 47, 78-93; doi:10.1016/j.jaerosci.2012.01.001 .

Electrospinning

 

Highly aligned nanofibers by electrospinning

When a strong electric field is applied to a viscous polymer solution, the solution often forms thin fibers, typically under micrometer scale in width. As they form, electrospun fibers tend to whip wildly in the air. We have shown that it is possible to eliminate completely this whipping by configuring the electrodes appropriately and collecting the fibers onto fast-rotating cylindrical collectors. This leads to perfect alignment of nanofibers on the collector, which can be of interest in diverse applications requiring such asymmetrically nanostructured materials (for example, solvent vapor sensors, or vascular tissue engineering).

 

Whipping of an electrospun fiber shortly after forming moving from left to right (captured by a high speed camera

 

 

Examples of highly oriented electrospun nanofibers collected on a rotating cylinder.

 

 

Ion assisted electrospinning onto difficult-to-coat substrates

Electrospinning nanofibers directly over insulating substrates or substrates with a texture like meshes results in poor and non-uniform coverage. These effects are due to surface charge accumulation. We have developed a methodology that leads to uniform nanofiber coatings which is valid on all kinds of substrates. The method is based on rapid sequential deposition of electrospun nanofibers and oppositely charged ions. This work has been carried out in collaboration with Jan Uecker and Prof. Gary Tepper of Virginia Commonwealth University (USA).

 

...Film of nanofibers deposited over a polyester felt made of much thicker threads. A few polyester threadscan be hintedbeneath the nano-fibrous film.

Hidrotalcites on Carbon nanofibers

Electrospinning is the art of making nanofibers using electrostatic fields, and is akin to the art of electrospray. We have synthesized various structures using electrospinning. For example, carbon-supported hydrocalcites can be formde by carboniation and subsequent hydration of electrospun PVA/PEO/MgAl-nitrate fibers. This rpoject has been developed in collaboration with the Heterogenous Catalysis Group of The Universitat Rovira i Virgili (Spain).

 

Publications

Luis B. Modesto‐López, Ricardo J. Chimentão, Mayra G. Álvarez, Joan Rosell‐Llompart, Francisco Medina, Jordi Llorca. 2014. “Direct growth of hydrotalcite nanolayers on carbon fibers by electrospinning”, Applied Clay Science, 101, 461‐467.

P. Kiselev and J. Rosell-Llompart. 2012. “Highly Aligned Electrospun Nanofibers by Elimination of the Whipping Motion”, Journal of Applied Polymer Science, 125(3), 2433-2441.

J. Uecker, G.C. Tepper, and J. Rosell-Llompart. 2010. “Ion-Assisted Collection of Nylon-4,6 Electrospun Nanofibers”, Polymer, 51(22), 5221-5228.

 

Aerosol Technology

- Flow burring

 

Flow blurring is anovel method for efficient pneumatic liquid atomization. In pneumatic spraying the energy needed for liquid fragmentation is supplied in the form of gas pressure (enthalpy). Flow blurring was co-invented by Prof. Gañán Calvo and Joan Rosell during collaborative R&D between Aradigm Corporation and Universidad de Sevilla. It has industrially been applied in the ICP-MS One-Neb™ atomizer.

Whipping of an electrospun fiber shortly after forming moving from left to right (captured by a high speed camera

 

 

Recent Publications in Aerosol Technology research field.

Rosell-Llompart, J., Gañán Calvo, A.(2008).Turbulence in Pneumatic Flow Focusing and Flow Blurring Regimes, Physical Review , 77(3), 036321.

 

Publications

  • M.G.Álvarez, R.J.Chimentão, D.Tichit, J.B.O.Santos, A.Dafinov, L.B.Modesto-López, J.Rosell-Llompart, E. J.Güell, F.Gispert-Guirado, J.Llorca, F.Medina (2016). Synthesis of tungsten carbide on Al-SBA-15 mesoporous materials by carburization.Microporous and Mesoporous Materials, 219, 19-28. doi:10.1016/j.micromeso.2015.07.018
  • Kumar Arumugham-Achari, A., Grifoll, J., Rosell-Llompart, J. (2015). A comprehensive framework for the numerical simulation of evaporating electrosprays. Aerosol Science and TechnologyDOI:10.1080/02786826.2015.1039639 . If you do not have access to this journal, you can download a copy for free using this link:http://www.tandfonline.com/eprint/pEmqPUh96hySk2JINVhc/full
  • Serres, J. M., Mateos, X., Loiko, P., Rosell Llompart, J., Modesto-López, L. B., Yumashev, K. V.,Griebner, U., Petrov, V., Carvajal, J. J., Aguiló, M. and Díaz, F. (2015). Oriented Single Walled Carbon Nanotubes as Saturable Absorber for Passive Q-Switching of a Tm:KLuW Microchip Laser. Advanced Solid State Lasers, OSA Technical Digest (ISBN: 978‐1‐943580‐02‐6) paper AW1A.3. doi:10.1364/ASSL.2015.AW1A.3
  • Álvarez, M. G., Chimentão, R. J., Tichit, D., Santos, J. B. O., Dafinov, A., Modesto-López, L. B., Rosell Llompart, J., Güell, E. J., Gispert Guirado, F., Llorca, J. and Medina, F. (2016). Synthesis of Tungsten Carbide on Al-SBA-15 Mesoporous Materials by Carburization. Microporous and Mesoporous Materials, 219, 19-28. doi:10.1016/j.micromeso.2015.07.018
  • Modesto-López, L.,Chimentão, R.,Álvarez, M., Rosell-Llompart, J., Medina Cabello, F., Llorca, J. (2014). Direct growth of hydrotalcite nanolayers on carbon fibers by electrospinning. Applied Clay Science, 101, 461–467
  • Grifoll, J., Rosell-Llompart, J. (2014). Continuous droplets' charge method for the Lagrangian simulation of electrostatic sprays. Journal of Electrostatics. 72(5),357-364. doi: 10.1016/j.elstat.2014.06.011
  • Bodnár, E., Rosell-Llompart, J.(2013). Growth dynamics of granular films produced by electrospray. Journal of colloid and interface science, 407, 536–545
  • Kumar Arumugham-Achari, A., Grifoll, J., Rosell-Llompart, J.(2013). Two-way coupled numerical simulation of electrospray with induced gas flow. Journal of Aerosol Science, 65, 121–133
  • Grifoll, J.(2013). Contribution of mechanical dispersion of vapor to soil evaporation. Water Resources Research. 49 (2), 1099-1106, DOI: 10.1002/wrcr.20105.
  • Kiselev, P., Rosell-Llompart, J.(2012).Highly aligned electrospun nanofibers by elimination of the whipping motion. Journal of Applied Polymer Science, 125(3), 2433-2441
  • Grifoll, J., Rosell-Llompart, J.(2012). Efficient Lagrangian simulation of electrospray droplets dynamics.Journal of Aerosol Science, 47, 78-93
  • Publications by the Senior members of the research group can be found in their personal web pages.
  • Dr. Joan Rosell
  • Dr. Jordi Grifoll
  •