(374e) Innovating Soft Matter Manipulation with Fibrous Nonwovens: Integrating Computational Design and Experimental Insights for Pore-Scale Electrokinetic Applications

Field-induced electrical manipulation of soft matter extends into the micro-scale, made possible by technological advances in micro-fabrication methods [1]. Techniques such as contact lithography can be used to reliably produce spatial arrays of micro-electrodes[2], manipulate micron- and nano-scale particles, cells, and biomolecules in liquid suspension using the induced-charge electrokinetic phenomenon [3], dielectrophoresis (DEP) [4]. However, due to the required micron-scale electric field gradients to induce soft matter DEP, such manipulations have proven extremely difficult to perform across larger length (> 100 µm) and volumetric (>100 µL) scales which severely limit the impact and applicability of this method. Thus, there is a need to develop a fundamental understanding for how to utilize low-cost porous paper-like materials, which naturally possess micron-scale features capable of inducing DEP, as robust substrates for soft matter DEP manipulations [5].

Motivated by this need, we have developed a new class of DEP substrate using low-cost synthetic fibrous porous materials with reliable and predictable sources of localized electric field gradients. The converging-diverging nature of the intersecting fibers creates a network of tortuous pores which, when subjected to an external field, is used to generate pore-scale electric field gradients capable of manipulating soft matter suspensions dielectrophoretically. The porous nonwoven DEP method is then used to trap bioparticles, such as DNA. Proteins and E. coli cells in the substrate pores over a range of applied potentials (2 to 10 V).

To further improve the porous network, we developed a physics-based high-fidelity model that predicts electric field pockets within nonwoven fiber microfluidic pore-spaces and integrate it with a flow model to determine how fluid flow affects particle trapping. We used a stochastic numerical analysis to compute grouped frequency distributions of the substrates pore-scale properties, including the electric field strength and the electric field gradient. This was done to quantify the dielectrophoretic potential of each substrate, and to understand the degree of variation and nonuniformity across the substrate. This the framework could be leveraged to design substrates for biomolecular enrichment of proteins and nucleic acids, which are crucial for liquid biopsy applications.

References

[1] D. Qin, Y. Xia, and G. M. Whitesides, “Soft lithography for micro- and nanoscale patterning,” Nature Protocols 2010 5:3, vol. 5, no. 3, pp. 491–502, Feb. 2010.

[2] D. Monserrat Lopez et al., “Direct electrification of silicon microfluidics for electric field applications,” Microsystems & Nanoengineering 2023 9:1, vol. 9, no. 1, pp. 1–13, Jun. 2023.

[3] M. Z. Bazant and T. M. Squires, “Induced-charge electrokinetic phenomena,” Curr Opin Colloid Interface Sci, vol. 15, no. 3, pp. 203–213, Jun. 2010.

[4] Z. R. Gagnon, “Cellular dielectrophoresis: Applications to the characterization, manipulation, separation and patterning of cells,” Electrophoresis, vol. 32, no. 18, pp. 2466–2487, Sep. 2011.

[5] M. N. Islam, B. Jaiswal, and Z. R. Gagnon, “High-Throughput Continuous Free-Flow Dielectrophoretic Trapping of Micron-Scale Particles and Cells in Paper Using Localized Nonuniform Pore-Scale-Generated Paper-Based Electric Field Gradients,” Anal Chem, vol. 96, no. 3, pp. 1084–1092, Jan. 2024.