The sensitivity and speed with which the immune system reacts to host disruption is unrivaled by any detection method for pathogenic biomarkers or infectious signatures. Engagement of cellular immunity in response to infections or cancer is contingent upon activation and subsequent cytotoxic activity by T cells. Thus, monitoring T cell activation can reliably serve as a metric for disease diagnosis as well as therapeutic prognosis. Rapid and direct quantification of T cell activation states, however, has been hindered by challenges associated with antigen target identification, labeling requirements, and assay duration. Here we present an electronic, label-free method for simultaneous separation and evaluation of T cell activation states. Our device utilizes a microfluidic design integrated with nanolayered electrode structures for dielectrophoresis (DEP)-driven discrimination of activated vs naïve T cells at single-cell resolution and demonstrates rapid (<2 min) separation of T cells at high single-pass efficiency as quantified by an on-chip Coulter counter module. Our device represents a microfluidic tool for electronic assessment of immune activation states and, hence, a portable diagnostic for quantitative evaluation of immunity and disease state. Further, its ability to achieve label-free enrichment of activated immune cells promises clinical utility in cell-based immunotherapies.

Smart-agriculture technologies comprise a set of management systems designed to sustainably increase the efficiency and productivity of farming. In this paper, we present a lab-on-a-chip device that can be employed...

Ion–surface interactions can alter the properties of nanopores and dictate nanofluidic transport in engineered and biological systems central to the water–energy nexus. The ion adsorption process, known as “charge regulation”, is ion-specific and is dependent on the extent of confinement when the electric double layers (EDLs) between two charged surfaces overlap. A fundamental understanding of the mechanisms behind charge regulation remains lacking. Herein, we study the thermodynamics of charge regulation reactions in 20 nm SiO2 channels via conductance measurements at various concentrations and temperatures. The effective activation energies (E a) for ion conductance at low concentrations (strong EDL overlap) are ∼2-fold higher than at high concentrations (no EDL overlap) for the electrolytes studied here: LiCl, NaCl, KCl, and CsCl. We find that E a values measured at high concentrations result from the temperature dependence of viscosity and its influence on ion mobility, whereas E a values measured at low concentrations result from the combined effects of ion mobility and the enthalpy of cation adsorption to the charged surface. Notably, the E a for surface reactions increases from 7.03 kJ mol–1 for NaCl to 16.72 ± 0.48 kJ mol–1 for KCl, corresponding to a difference in surface charge of −8.2 to −0.8 mC m–2, respectively. We construct a charge regulation model to rationalize the cation-specific charge regulation behavior based on an adsorption equilibrium. Our findings show that temperature- and concentration-dependent conductance measurements can help indirectly probe the ion–surface interactions that govern transport and colloidal interactions at the nanoscalerepresenting a critical step forward in our understanding of charge regulation and adsorption phenomena under nanoconfinement.

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Carbon nanotube porins (CNTPs) are biomimetic membrane channels that demonstrate excellent biocompatibility and unique water and ion transport properties. Gating transport in CNTPs with external voltage could increase control over ion flow and selectivity. Herein, we used continuum modeling to probe the parameters that enable and further affect CNTP gating efficiency, including the size and composition of the supporting lipid membrane, slip flow in the carbon nanotube, and the intrinsic electronic properties of the nanotube. Our results show that the optimal gated CNTP device consists of a semiconducting CNTP inserted into a small membrane patch containing an internally conductive layer. Moreover, we demonstrate that the ionic transport modulated by gate voltages is controlled by the charge distribution along the CNTP under the external gate electric potential. The theoretical understanding developed in this study offers valuable guidance for the design of gated CNTP devices for nanofluidic studies, novel biomimetic membranes, and cellular interfaces in the future.