Publications
A Gram–Charlier analysis of scattering to describe nonideal polymer conformations
A. Datta, X. Wang, S. D. Mengel, A. J. DeStefano, R. A. Segalman, P. T. Underhill, M. E. Helgeson, Macromolecules, 57, 9518-9535, 2024.
We propose a moments analysis based on the Gram–Charlier expansion as a natural framework for describing structure and scattering from non-Gaussian polymers. The expansion describes the conformation distribution in terms of cumulants of the underlying segment density distribution function, providing low-dimensional descriptors that can be inferred directly from measured scattering in a way that is agnostic to a polymer’s topology, chemistry, or state of deformation. We use this framework to show that cumulants can be used to “fingerprint” non-Gaussian conformation distributions of polymers either at equilibrium or out of equilibrium.
Reduction of monoclonal antibody viscosity using interpretable machine learning
E. K. Makowski, H.-T. Chen, T. Wang, L. Wu, J. Huang, M. Mock, P. T. Underhill, E. Pelegri-O’Day, E. Maglalang, D. Winters, P. M. Tessier, mAbs, 16, 2303781, 2024.
Decision tree model is developed to classify monoclonal antibodies into high or low risk for having a high viscosity. Based on the model, we identify changes to molecules that have high viscosity which are predicted to lower the viscosity. Measurements on these changed molecules are used to validate the model.
Stochastic kinetic theory applied to coarse-grained polymer model
S. Zhu and P. T. Underhill, J. Chem. Phys., 160, 114903, 2024.
A stochastic field theory approach is applied to a coarse-grained polymer model. We validate the new model under conditions with analytical solutions. The full field theory is only accurate for large numbers of polymers. For fewer numbers of polymers we use a moment closure to produce an accurate and computationally efficient model.
A new class of “structure-by-design” polymer membranes for organic solvent nanofiltration with controllable selectivity
P. Ramesh, M. M. Sta Cruz, S. Karla, J. Ahn, S. Lee, P. T. Underhill, G. Belfort, J. Mem. Sci., 692, 122296, 2024.
We use experiments and atomistic simulations to create and quantify the behavior of polymer brush membranes. The use of different monomers alters the structure of the polymer layer which results in different selectivity in organic solvent nanofiltration.
Swimming in complex fluids
S. E. Spagnolie and P. T. Underhill, Annu. Rev. Condens. Matter Phys., 14, 381-415, 2023.
We review the literature on swimming in complex fluids. A classification is proposed by comparing the length- and timescales of a swimmer with those of nearby obstacles. For each of the eight system types that we identify, we provide a background and describe modern research findings. Although some types have seen a great deal of attention for decades, others remain uncharted waters still open and awaiting exploration.
J. Zhang, G. S. Smith, P. T. Corona, P. T. Underhill, L. G. Leal, M. E. Helgeson. "Self-consistent connected-rod model for small-angle scattering from deformed semiflexible chains in flow", Macromolecules, 57, 201-216, 2023. link
J. Ahn, L. Chen, P. T. Underhill, G. Freychet, M. Zhernenkov, and S. Lee. "Continuous transition of colloidal crystals through stable random orders", Soft Matter, 19, 3257-3266, 2023. link
S. S. Virk and P. T. Underhill. "Application of a simple short-range attraction and long-range repulsion colloidal model toward predicting the viscosity of protein solutions", Mol. Pharmaceutics, 19, 4233-4240, 2022. link
E. M. Tang, S. S. Virk, and P. T. Underhill. "Coupling between long ranged repulsions and short ranged attractions in a colloidal model of zero shear rate viscosity", J. Rheology, 66, 491-504, 2022. link
T. O. Bello, S. Lee, and P. T. Underhill. "Mesoscale simulation approach for assembly of small deformable objects", Soft Matter, 18, 5106-5113, 2022. link
A. C. Setaro and P. T. Underhill. "Dumbbell kinetic theory for polymers in a combination of flow and external electric field", Phys. Rev. E, 100, 052501, 2019. link
A. Raghunandan, A. H. Hirsa, P. T. Underhill, J. M. and Lopez. "Predicting steady shear rheology of condensed-phase monomolecular films at the air-water interface", Phys. Rev. Lett., 121, 164502, 2018. link
E. M. Tang and P. T. Underhill. "Examination of the statistical effects associated with tracking propulsive particles", Langmuir, 34, 10694-10701, 2018. link
P. Chatterjee, E. M. Tang, P. Karande, P. T. and Underhill. "Propulsion of catalytic Janus spheres in viscosified Newtonian solutions", Phys. Rev. Fluids, 3, 014101, 2018. link
J. J. Keating, M. Sorci, I. Kocsis, A. Setaro, M. Barboiu, P. T. Underhill, G. and Belfort. "Atmospheric pressure plasma - ARGET ATRP modification of poly(ether sulfone) membranes: A combination attack", J. Mem. Sci., 546, 151-157, 2018. link
P. Chatterjee, G. Sowiak, and P. T. Underhill. "Effect of phase change on the rheology and stability of paraffin wax-in-water Pickering emulsions", Rheol. Acta, 56, 601-613, 2017. link
Y. Qian, P. R. Kramer, and P. T. Underhill. "Stochastic kinetic theory for collective behavior of hydrodynamically interacting active particles", Phys. Rev. Fluids, 2,043104, 2017. link
P. T. Underhill, A. H. Hirsa, and J. M. Lopez. "Modeling steady shear flows of Newtonian liquids with non-Newtonian interfaces", J. Fluid Mech., 814, 5-23, 2017. link
H. Pandey, S. Szafran, and P. T. Underhill. "Passive trapping of rigid rods due to conformation-dependent electrophoretic mobility", Soft Matter, 12, 3121-3126, 2016. link
H. Pandey and P. T. Underhill. "Coarse-grained model of conformation-dependent electrophoretic mobility and its influence on DNA dynamics", Phys. Rev. E, 92, 052301, 2015. link
L. Ren, R. Ozisik, S. P. Kotha, and P. T. Underhill. "Highly efficient fabrication of polymer nanofiber assembly by centrifugal jet spinning: process and characterization", Macromolecules, 48, 2593-2602, 2015. link
R. Radhakrishnan and P. T. Underhill. "Influence of shear on globule formation in dilute solutions of flexible polymers", J. Chem. Phys., 142, 144901, 2015. link
S. Chilukuri, C. H. Collins, and P. T. Underhill. "Dispersion of flagellated swimming microorganisms in planar Poiseuille flow", Phys. Fluids, 27, 031902, 2015. link
Y. Bozorgi and P. T. Underhill. "Large amplitude oscillatory shear rheology of dilute active suspensions", Rheol. Acta, 53, 899-909, 2014. link
Y. Bozorgi and P. T. Underhill. "Effects of elasticity on the nonlinear collective dynamics of self-propelled particles", J. Non-Newtonian Fluid Mech., 214, 69-77, 2014. link
S. Chilukuri, C. H. Collins, and P. T. Underhill. "Impact of external flow on the dynamics of swimming microorganisms near surfaces", J. Phys.: Condens. Matter, 26, 115101, 2014. link
R. Radhakrishnan and P. T. Underhill. "Simulations of the large amplitude oscillatory shear response of polymer-colloid globules", AIChE J., 60, 1365-1371, 2014. link
P. T. Underhill. "Viscosity/rheological measurements", in Colloid and Surface Chemistry: A Laboratory Guide for Exploration of the Nano World, Seyda Bucak and Deniz Rende, editors, CRC Press, 41-49, 2013. link
R. Radhakrishnan and P. T. Underhill. "Fluctuations in the coil-stretch transition of flexible polymers in good solvents: A peak due to non-linear force relation", Phys. Rev. E, 88, 012606, 2013. link
Y. Bozorgi and P. T. Underhill. "Role of linear viscoelasticity and rotational diffusivity on the collective behavior of active particles", J. Rheol., 57, 511-533, 2013. link
R. Radhakrishnan and P. T. Underhill. "Impact of solvent quality on the hysteresis in the coil-stretch transition of flexible polymers in good solvents", Macromolecules, 46, 548-554, 2013. link
R. Radhakrishnan and P. T. Underhill. "Models of flexible polymers in good solvents: relaxation and coil-stretch transition", Soft Matter, 8, 6991-7003, 2012. link
Y. Bozorgi and P. T. Underhill. "Effect of viscoelasticity on the collective behavior of swimming microorganisms", Phys. Rev. E, 84, 061901, 2011. link
P. T. Underhill and M. D. Graham. "Correlations and fluctuations of stress and velocity in suspensions of swimming microorganisms", Phys. Fluids, 23, 121902, 2011. link
Publications prior to joining RPI
J. P. Hernandez-Ortiz, P. T. Underhill, and M. D. Graham. "Dynamics of confined suspensions of swimming particles", J. Phys.: Condens. Matter, 21, 204107, 2009. link
P. T. Underhill, J. P. Hernandez-Ortiz, and M. D. Graham. "Diffusion and spatial correlations in suspensions of swimming particles", Phys. Rev. Lett., 100, 248101, 2008. link
P. T. Underhill and P. S. Doyle. "Accuracy of bead-spring chains in strong flows", J. Non-Newtonian Fluid Mech., 145, 109-123, 2007. link
P. T. Underhill and P. S. Doyle. "DNA stretch during electrophoresis due to a step change in mobility", Phys. Rev. E, 76, 011805, 2007. link
P. T. Underhill and P. S. Doyle. "Alternative spring force law for bead-spring chain models of the worm-like chain", J. Rheol., 50, 513-529, 2006. link
P. T. Underhill and P. S. Doyle. "Development of bead-spring polymer models using the constant extension ensemble", J. Rheol., 49, 963-987, 2005. link
P. S. Doyle and P. T. Underhill. "Brownian dynamics simulations of polymers and soft matter", in Handbook on Materials Modeling, Volume I: Methods and Models, Sidney Yip, editor, 2619-2630, 2005. link
P. T. Underhill and P. S. Doyle. "On the coarse-graining of polymers into bead-spring chains", J. Non-Newtonian Fluid Mech., 122, 3-31, 2004. link
W. Bauer, S. Pratt, C. Morling, and P. Underhill. "The nuclear fragmentation phase transition and rare isotope production", Heavy Ion Physics, 14, 29-38, 2001. link
S. Pratt, W. Bauer, C. Morling, and P. Underhill. "Rare isotope production in statistical multifragmentation", Phys. Rev. C, 63, 034608, 2001. link
D. B. Hall, P. Underhill, and J. M. Torkelson. "Spin coating of thin and ultrathin polymer films", Polym. Eng. Sci., 38, 2039-2045, 1998. link