## CLAUDIA VENDITTI

Dottoressa di ricerca**ciclo**: XXXV

**supervisore**: Prof. Alessandra Adrover

**Titolo della tesi:**On the effect of particle size and inertia, wall hydrodynamic confinement and surface adsorption/desorption on particle motion in microfluidic devices.

The analysis of dispersion properties, evaluated with local and integral moment analysis, is here used to quantify the effect of particle size and inertia, wall hydrodynamic confinement and surface adsorption/desorption on particle motion in microfluidic devices.
The inertial regime of non-interacting Brownian particles in the washboard potential is investigated, when the overdamped approximation does not yield accurate predictions. Different reduced models of increasing complexity, improving the overdamped approximation, are developed starting from the basic assumption that the velocity variable can be split into an "almost" deterministic and a fully stochastic contribution. The almost deterministic velocity term can be estimated from a fully deterministic or from a stochastic slow inertial manifold.
The effective particle velocity field, described by a slow/inertial manifold, is estimated for the dynamics of finite-sized particles with large inertia in steady and time-dependent open and closed flows. The numerical solution of the invariance equation describing the space-time evolution of the inertial manifold allows for an accurate reconstruction of the effective particle divergence field controlling clustering/dispersion features of particles, for which a perturbative approach is inaccurate or even not convergent. The effect of inertia is quantified in terms of the rate of contraction/expansion of volume elements along a particle trajectory and of the maximum Lyapunov exponent for systems exhibiting chaotic orbits.
The hydrodynamic effects on finite-size particles are evaluated in the Brownian Sieving Microcapillary Hydrodynamic Chromatography device (BS-MHDC), an unconventional double-channel device. The separation performance is investigated adopting a two-way coupling approach, and results are compared with those obtained with the one-way coupling (excluded volume) analysis. The latter overestimates the separation performance with respect to the two-way coupling analysis, but, the enhancement factor of the BS-MHDC over the standard MHDC is underestimated by the single-phase approximation as it doubles when wall/particle interactions are properly accounted for with a two-phase description.
Dispersion properties of point-size particles are also investigated when an adsorption/desorption process occurs at the device walls. As a first case of study, the separation performance in Open-Tubular Liquid Chromatography is evaluated in the presence of transversal flows, possessing regular or chaotic streamlines, thus showing that the presence of cross-flows can lower sensitively the dependence of the column length on the P\'{e}clet number. Flows possessing chaotic streamlines prove the most efficient choice at large eluent velocities and low values of the column adsorption constant.
The dispersion of an analyte in a sinusoidal channel with adsorbing/desorbing walls and in the retentive pillar array column for liquid chromatography are taken as case studies for the exact local and integral moment approach, representing a significant improvement of the classical Brenner's theory as it allows to investigate the temporal evolution of effective dispersion properties of solute particles in periodic media possessing impermeable walls as well as absorbing/desorbing walls. The transient analysis of dispersion properties shows that the adsorption/desorption process strongly amplifies the phenomenon of the overshoot for the effective dispersion coefficient. Moreover, the method proposed allows for a detailed analysis of the temporal evolution of the skewness of the marginal distribution of the analyte along the main stream direction, thus permitting an accurate and reliable estimate of the time-scale for achieving the macro-transport regime, that implies a Gaussian (symmetric) marginal pdf.

**Produzione scientifica**

- 11573/1676781 - 2023 - Fractionation of a three-particle mixture by Brownian sieving hydrodynamic chromatography (01a Articolo in rivista)

BIAGIONI, VALENTINA; VENDITTI, CLAUDIA; ADROVER, ALESSANDRA; CERBELLI, STEFANO - 11573/1682767 - 2023 - Moment analysis for predicting effective transport properties in hierarchical retentive porous media (01a Articolo in rivista)

VENDITTI, CLAUDIA; ADROVER, ALESSANDRA - 11573/1341319 - 2019 - On the long-term simulation of stochastic differential equations for predicting effective dispersion coefficients (01a Articolo in rivista)

GIONA, MASSIMILIANO; VENDITTI, CLAUDIA; ADROVER, ALESSANDRA - 11573/1691768 - 2023 - Nonadditivity and Nonlinearity of Mobile and Stationary Zone Mass Transfer Resistances in Chromatography (01a Articolo in rivista)

VENDITTI, CLAUDIA; ADROVER, ALESSANDRA - 11573/1332366 - 2019 - Exact moment analysis of transient dispersion properties in periodic media (01a Articolo in rivista)

ADROVER, ALESSANDRA; VENDITTI, CLAUDIA; GIONA, MASSIMILIANO - 11573/1280058 - 2019 - Laminar dispersion at low and high Peclet numbers in a sinusoidal microtube: point-size versus finite-size particles (01a Articolo in rivista)

ADROVER, ALESSANDRA; VENDITTI, CLAUDIA; GIONA, MASSIMILIANO - 11573/1450238 - 2020 - A non-isothermal moving-boundary model for continuous and intermittent drying of pears (01a Articolo in rivista)

ADROVER, ALESSANDRA; VENDITTI, CLAUDIA; BRASIELLO, ANTONIO - 11573/1530212 - 2021 - Swelling and drug release in polymers through the theory of Poisson–Kac stochastic processes (01a Articolo in rivista)

ADROVER, ALESSANDRA; VENDITTI, CLAUDIA; GIONA, MASSIMILIANO - 11573/1571250 - 2022 - Inertial effects and long-term transport properties of particle motion in washboard potential (01a Articolo in rivista)

VENDITTI, CLAUDIA; ADROVER, ALESSANDRA; GIONA, MASSIMILIANO - 11573/1627738 - 2022 - On the dynamic role of energy in underdamped particle motion (01a Articolo in rivista)

VENDITTI, CLAUDIA; ADROVER, ALESSANDRA; GIONA, MASSIMILIANO - 11573/1612016 - 2022 - L'articolo Invariant manifold approach for quantifying the dynamics of highly inertial particles in steady and time-periodic incompressible flows
Chaos 32, 023121 (2022); https://doi.org/10.1063/5.0081556 è stato selezionato come Editor's pick della rivista AIP Chaos (14a Premio o riconoscimento scientifico)

VENDITTI, CLAUDIA; GIONA, MASSIMILIANO; ADROVER, ALESSANDRA - 11573/1628885 - 2022 - Comparison between one- and two-way coupling approaches for estimating effective transport properties of suspended particles undergoing Brownian sieving hydrodynamic chromatography (01a Articolo in rivista)

VENDITTI, CLAUDIA; CERBELLI, STEFANO; PROCOPIO, GIUSEPPE; ADROVER, ALESSANDRA - 11573/1628891 - 2022 - Featured paper Physics of Fluids 2022 (14a Premio o riconoscimento scientifico)

VENDITTI, CLAUDIA; ADROVER, ALESSANDRA; CERBELLI, STEFANO; PROCOPIO, GIUSEPPE - 11573/1658825 - 2022 - Taming Taylor-Aris dispersion through chaotic advection (01a Articolo in rivista)

BIAGIONI, VALENTINA; VENDITTI, CLAUDIA; ADROVER, ALESSANDRA; GIONA, MASSIMILIANO; CERBELLI, STEFANO - 11573/1612012 - 2022 - Invariant manifold approach for quantifying the dynamics of highly inertial particles in steady and time-periodic incompressible flows (01a Articolo in rivista)

VENDITTI, CLAUDIA; GIONA, MASSIMILIANO; ADROVER, ALESSANDRA - 11573/1663504 - 2022 - Exact moment analysis of transient/asymptotic dispersion properties in periodic media with adsorbing/desorbing walls (01a Articolo in rivista)

VENDITTI, CLAUDIA; GIONA, MASSIMILIANO; ADROVER, ALESSANDRA - 11573/1658368 - 2022 - Impact of transversal vortices on the performance of open-tubular liquid chromatography (01a Articolo in rivista)

VENDITTI, CLAUDIA; BIAGIONI, VALENTINA; ADROVER, ALESSANDRA; CERBELLI, STEFANO - 11573/1571237 - 2021 - Non-isothermal moving-boundary model for food drying (01a Articolo in rivista)

BRASIELLO, ANTONIO; VENDITTI, CLAUDIA; ADROVER, ALESSANDRA