10. Shankar P. Kharal, Mohib Mohibullah,  Tori McDermott, Christopher J. Easley, and Jean Francois Louf, Hydraulic Optimization in Physarum Polycephalum: Pathfinding Beyond the Shortest Route, submitted, under review,  (Research Areas: Complex Fluids, Living & Active system)

In self-organizing systems like the slime mold Physarum polycephalum, growth patterns arise from the interplay between physical constraints and active behavior. Using microfluidic bifurcating channels with independently tunable length and hydraulic resistance, we show that Physarum consistently selects the path of least hydraulic resistance (even when longer) and that its locomotion shifts from sustained growth to intermittent “Run and Tumble” as confinement increases, captured by a confinement factor based on channel cross-section. By decoupling resistance from geometric constraint, we demonstrate that path choice and motility are governed by distinct physical cues, offering a mechanistic framework for environment-dependent navigation and a physical basis for bioinspired routing algorithms in confined environments.

9. Aihik Banerjee, Anjana Khanal, Prince D. Okoro, Shankar P. Kharal, Kevin Dalsania, Baishali Kanjilal, Shiril B. Iragavarapu, Yiqing Chen, Janitha M. Unagolla, Huinan H. Liu, Joshua T. Morgan, Robert P. Hesketh, Arash Pezhouman, Reza Ardehali, Bahman Anvari, Martin F. Haase, Iman Noshadi, Highly Interconnected Porous Bicontinuous Interfacially Jammed Emulsion Biomaterials for Tissue Engineering and Regenerative Medicine, Small Science , 2025, (pdf) , (Research areas: Bijels & Tissue Engineering)

In this study, we develop a BIJEL-Integrated PORous Engineered System (BIPORES) that imparts bioinert PEGDA with bicontinuous interconnected porosity and complex surface topography via controlled phase separation and nanoparticle-stabilized interfaces, effectively mimicking key features of the natural extracellular matrix. We demonstrate that BIPORES scaffolds support robust attachment, growth, proliferation, and differentiation of human mesenchymal stem cells and hiPSC-derived cardiac cells, highlighting how bicontinuous porosity with negative Gaussian curvature can enable organ-scale tissue engineering and regeneration. 

8. Yawei Gao, Ajay Jayswal, Arit Das, Jan Michael Y Carrillo, Joshua T Damron, Christopher C Bowland, Zeyang Yu, Michael Toomey, Polyxeni P Angelopoulou, Shankar Kharal, Gamini Mendis, Holly Humphrey, Bobby G Sumpter, Logan T Kearney, Amit K Naskar, Enhanced Interfacial Bonding of Graft Copolymers, ACS Applied Materials & Interfaces, 2025,  (pdf)  (Research Areas: Polymer, coating and composite materials)

In this study, we combine coarse-grained molecular dynamics simulations with experimental lap-shear tests to reveal how polymer topology—from linear to grafted comb and bottlebrush architectures—governs interfacial diffusion, welding kinetics, and ultimate rupture strength, with dense bottlebrushes achieving faster but lower-saturation strength due to rapid side-chain interdigitation and entropic van der Waals contacts. We further show that the deformation and failure behavior transitions from brittle (linear/comb) to elastomeric (bottlebrush), highlighting how tailored macromolecular architecture can be leveraged to tune welding mechanisms and mitigate interface anisotropy in advanced manufacturing processes such as fused filament fabrication.

7. Shankar P. Kharal, Nicholas J. Jones, and Gabriella Petculescu, Sensitization of 5XXX Series Aluminum Alloys explored with an adapted JMAK model for phase evolution and ultrasonics, CORROSION-The Journal of Science and Engineering, 2024 (pdf) (Research Areas: Acoustics, Al5xxx alloys, & NDT)

In this study, we apply a Johnson-Mehl-Avrami-Kolmogorov framework to relate phase transformations during sensitization in 5xxx series aluminum alloys to changes in longitudinal and shear wave speeds and attenuation, extracting rate constants k and Avrami exponents n that are consistent with independently measured phase velocities and Arrhenius trends, and that show AA5456 reaches full sensitization faster than AA5083. We further demonstrate that discrepancies between k values from attenuation and wave-speed data highlight the role of scattering in acoustic losses, while n values of 1–2 (increasing toward higher values at the highest processing temperature) indicate predominantly 1D/2D β-phase growth along grain boundaries and their intersections, with partial 3D growth at elevated temperatures.

6. Shankar P. Kharal and Jean Francois  Louf, Unidirectional Freezing of polymer solution droplets, Langmuir, 2023 (pdf), (Research Areas: Phase-separation, Polymers, Freezing)

In this study, we use ice templating of polymer–water droplets to tune and even suppress the “universal” pointy tip that typically forms when pure water droplets freeze on a substrate. We show that increasing polymer concentration progressively blunts the tip and ultimately removes it above the overlap concentration, while slowing the overall freezing, and we capture this behavior with a simple geometrical and heat-flux-based model that links shape evolution and solidification dynamics under unidirectional freezing. Together, these insights provide new routes to control frozen droplet morphology for ice-templated microstructure fabrication in applications such as tissue engineering, separation membranes, and soft robotics.

5. Mohammad A. Khan, Alessio J. Sprockel, Katherine A. MacMillan, Meyer T. Alting, Shankar P. Kharal, Stephen B. Ansah, and Martin F. Haase, Nanostructured, Fluid Bicontinuous Gels for Continuous Flow Liquid-Liquid Extraction,  Advanced Materials, 2022 (pdf), (Research Areas: Bicontinuous Emulsions)

In this study, we develop a scalable route to nanoparticle-stabilized fluid-bicontinuous gels with sub-500 nm channel sizes and very high specific surface areas (~2 m² cm⁻³), overcoming the traditional limitations of coarse fluid channels and static structures. We further demonstrate that liquids can be actively driven through these bicontinuous networks via electroosmosis, enabling fast flow for continuous liquid–liquid extraction. Together, these advances position fluid-bicontinuous gels as highly permeable porous media for applications such as microreaction platforms, fuel-cell components, and high-performance separation membranes.

4. Shankar P. Kharal, Martin F. Haase, Centrifugal Assembly of Helical Bijel Fibers for pH-Responsive Composite Hydrogels, Small, 2022 (pdf)  (Research areas: Centrifugal Assembly & Bicontinuous Emulsion) (Highlighted in the special series- "Rising Stars" on the webpage of Advanced Materials)

In this study, we reveal an unexpected role of centrifugal forces in microfluidics by using a rotating microcapillary to assemble helical soft-matter fibers that phase-separate into particle-stabilized bicontinuous interfacially jammed emulsion gels. By combining high-speed imaging with simulations, we show how density evolution reverses the effective centrifugal direction and use this insight to control helical fiber assembly into microropes that can be converted into pH-responsive hydrogels for tissue engineering, soft robotics, controlled release, and sensing, while more broadly highlighting centrifugal forces as a tool for directed self-assembly and separation of colloids, cells, and emulsions.

3. Shankar P. Kharal, Centrifugal assembly of bijel ropes via helical microfluidics, 2021, (PHD Thesis) (Research areas: Bijels, microfluidic-twisting, and centrifugal-assembly) (Won the Elizabeth Slater Award award for Excellence in Chemical Engineering Graduate Studies, 2022)

In this study, we use a microfluidic twisting method to transform weak bijel microfibers (tensile strengths of only a few kPa) into continuous micro-ropes whose strength is enhanced by up to four orders of magnitude while maintaining controllable architecture. By modeling the coupled rotational and translational shear stresses, we show how rope geometry and centrifugal-force direction govern the onset of undulations, and demonstrate that tuning the density contrast between the fiber casting mixture and co-flowing liquid suppresses these instabilities to yield uniform, continuously collectable microropes. This microfluidic twisting strategy opens a route to robust bijel-based composite fibers for flexible electronics, microrobotics, actuators, and tissue engineering, and provides a framework for twisting-driven assembly of particles, droplets, and cells.

2. Shankar P. Kharal, Robert P. Hesketh, and Martin F. Haase, High-tensile strength composite bijels through microfluidic twisting, Advanced Functional Material, 2020 (pdf) (Research areas: Bicontinuous emulsions, Microfluidic-Twisting)

In this study, we show that weak bijel microfibers with tensile strengths of only a few kilopascals can be transformed into continuous, flexible, and high-strength ropes using microfluidic (hydrodynamic) twisting. By modeling the fluid flow field, we link bundle geometry to a delicate balance between rotational and translational shear, and demonstrate that combining bijel fibers with polymeric support filaments boosts tensile strength to tens of megapascals while preserving liquid-like transport properties. This hydrodynamic twisting strategy opens a general route to composite ropes whose mechanical and functional performance exceeds the sum of their individual components.

1. Shankar P. Kharal, Modeling sensitization dynamics in Aluminum alloys 5000 series, 2018 (MS Thesis) (Research areas: Acoustics, RUS, PE)

In this study, we apply the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model to ultrasonic measurements to elucidate the crystallization kinetics of the β-phase in sensitized Al5083-H116 and Al5456-H116 alloys. By modeling longitudinal and transverse wave velocities and longitudinal attenuation as functions of time, we extract Avrami exponents that point to mixed 2D-to-1D growth along grain boundaries and their intersections, and phase transformation rate constants k that increase nonlinearly with heat-treatment temperature and are systematically higher for attenuation than for velocity. Together, these results show that acoustic parameters provide sensitive, quantitative probes of β-phase evolution and degree of sensitization in marine aluminum alloys.