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Xu Y, Brown KA. Direct pumping of polar fluids with traveling-wave dielectrophoresis. Electrophoresis 2023; 44:1655-1663. [PMID: 36641748 DOI: 10.1002/elps.202200231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/17/2022] [Accepted: 12/25/2022] [Indexed: 01/16/2023]
Abstract
Efficiently pumping fluids without moving parts in extremely miniaturized formats is challenging. Here, we propose and numerically explore a new type of fluid pump in which a series of electrodes driven at different phases produce a force directly on the molecules of the fluid. This effect is based on traveling-wave dielectrophoresis (twDEP), which has been observed to drive the motion of colloidal particles. Here, we leverage the time needed for fluid molecules with permanent dipoles to align with the applied field to maintain a phase lag between the applied field and the molecular polarization. While requiring operation in the GHz range, this effect is predicted to be efficient due to its ability to directly drive bulk fluid motion. We begin by establishing the foundational equations for this effect and performing finite element simulations to determine its magnitude in a model geometry. By combining theory and a systematic series of calculations, we validate that twDEP pumps should exhibit a fluid flow that scales as the voltage squared divided by the electrode period and that it should increase with the complex permittivity of the fluid and decrease with increasing viscosity. This results in a general equation that predicts the performance of twDEP pumps. Collectively, these computations provide a blueprint for producing twDEP pumps of polar fluids such as water and ethanol. We conclude by noting that the growing interest in high power microwave technology along with metasurfaces to locally tailor phase could provide a path to realizing twDEP pumps in practice.
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Affiliation(s)
- Yihong Xu
- Department of Physics, Boston University, Boston, Massachusetts, USA
| | - Keith A Brown
- Department of Physics, Boston University, Boston, Massachusetts, USA
- Department of Mechanical Engineering and Division of Materials Science & Engineering, Boston University, Boston, Massachusetts, USA
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Rendos A, Cao W, Chern M, Lauricella M, Succi S, Werner JG, Dennis AM, Brown KA. Electric field induced macroscopic cellular phase of nanoparticles. SOFT MATTER 2022; 18:1991-1996. [PMID: 35080230 DOI: 10.1039/d1sm01650d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A suspension of nanoparticles with very low volume fraction is found to assemble into a macroscopic cellular phase that is composed of particle-rich walls and particle-free voids under the collective influence of AC and DC voltages. Systematic study of this phase transition shows that it was the result of electrophoretic assembly into a two-dimensional configuration followed by spinodal decomposition into particle-rich walls and particle-poor cells mediated principally by electrohydrodynamic flow. This mechanistic understanding reveals two characteristics needed for a cellular phase to form, namely (1) a system that is considered two dimensional and (2) short-range attractive, long-range repulsive interparticle interactions. In addition to determining the mechanism underpinning the formation of the cellular phase, this work presents a method to reversibly assemble microscale continuous structures out of nanoscale particles in a manner that may enable the creation of materials that impact diverse fields including energy storage and filtration.
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Affiliation(s)
- Abigail Rendos
- Division of Materials Science & Engineering, Boston University, Boston, MA, USA.
| | - Wenhan Cao
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
| | - Margaret Chern
- Division of Materials Science & Engineering, Boston University, Boston, MA, USA.
| | - Marco Lauricella
- Istituto per le Applicazioni del Calcolo, Consiglio Nazionale delle Ricerche, via dei Taurini 19, Rome, 00185, Italy
| | - Sauro Succi
- Center for Life Nano-Neuro Science at La Sapienza, Rome, Italy
| | - Jörg G Werner
- Division of Materials Science & Engineering, Boston University, Boston, MA, USA.
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
| | - Allison M Dennis
- Division of Materials Science & Engineering, Boston University, Boston, MA, USA.
- Biomedical Engineering Department, Boston University, Boston, MA, USA
| | - Keith A Brown
- Division of Materials Science & Engineering, Boston University, Boston, MA, USA.
- Department of Mechanical Engineering, Boston University, Boston, MA, USA
- Physics Department, Boston University, Boston, MA, USA
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