Nanopores exhibit a set of interesting
transport properties that
stem from interactions of the passing ions and molecules with the
pore walls. Nanopores are used, for example, as ionic diodes and transistors,
biosensors, and osmotic power generators. Using nanopores is however
disadvantaged by their high resistance, small switching currents in
nA range, low power generated, and signals that can be difficult to
distinguish from the background. Here, we present a mesopore with
ionic conductance reaching μS that rectifies ion current in
salt concentrations as high as 1 M. The mesopore is conically shaped,
and its region close to the narrow opening is filled with high molecular
weight poly-l-lysine. To elucidate the underlying mechanism
of ion current rectification (ICR), a continuum model based on a set
of Poisson–Nernst–Planck and Stokes–Brinkman
equations was adopted. The results revealed that embedding the polyelectrolyte
in a conical pore leads to rectification of the effect of concentration
polarization (CP) that is induced by the polyelectrolyte, and observed
as voltage polarity-dependent modulations of ionic concentrations
in the pore, and consequently ICR. Our work reveals the link between
ICR and CP, significantly extending the knowledge of how charged polyelectrolytes
modulate ion transport on nano- and mesoscales. The osmotic power
application is also demonstrated with the developed polyelectrolyte-filled
mesopores, which enable a power of up to ∼120 pW from one pore,
which is much higher than the reported values using single nanoscale
pores.
Mechanical properties of cells are important features that are tightly regulated and are dictated by various pathologies. Deformability cytometry allows for the characterization of the mechanical properties at a rate of hundreds of cells per second, opening the way to differentiating cells via mechanotyping. A remaining challenge for detecting and classifying rare sub-populations is the creation of a combined experimental and analysis protocol that approaches the maximum potential classification accuracy for single cells. In order to find this maximum accuracy, we designed a microfluidic channel that subjects each cell to repeated deformations and relaxations and provides a comprehensive set of mechanotyping parameters. We track the shape dynamics of individual cells with high time resolution and apply sequence-based deep learning models for feature extraction. In order to create a dataset based solely on differing mechanical properties, a model system was created with treated and untreated HL60 cells. Treated cells were exposed to chemical agents that perturb either the actin or microtubule networks. Multiple recurrent and convolutional neural network architectures were trained using time sequences of cell shapes and were found to achieve high classification accuracy based on cytoskeletal properties alone. The best model classified two of the sub-populations of HL60 cells with an accuracy over 90%, significantly higher than the 75% we achieved with traditional methods. This increase in accuracy corresponds to a fivefold increase in potential enrichment of a sample for a target population. This work establishes the application of sequence-based deep learning models to dynamic deformability cytometry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.