Much of the success of nanoscale bioengineering relies on the development of new tools for probing minute amounts of liquids. Testing biofluids from and operation on individual cells, probing biofluids from primitive organisms ranging in size from fractions of microns to tens of microns, probing physiological fluids from secretory glands and microcapillaries, and collecting probes for forensic analyses are only a few examples of procedures in which nanoneedles and nanochannels are necessary instruments. In general, fibers with hierarchical pore structure are important in applications where liquid collection, transport, and analysis are performed on the same sample. Materials for these probes are required to have superior absorbency, controlled retention/extraction ability, and sufficient stiffness. To address these problems, we propose to develop one-dimensional probes with core-sheath morphology. We employ nanofiber yarns as cores. These yarns guarantee exceptional absorption and retention ability due to strong capillary action. As sheaths we suggest different materials with the common characteristic that the proposed sheaths effectively support liquid transport and provide sufficient stiffness. We also propose to graft the interior of the probe core with thermally responsive polymers. When slightly heated, the nanopores will decrease the level of hydrophilicity and push the liquid out of the pores. Therefore, the tested liquid will be released. In general, the results of this project are expected to set the basis for the design of novel fiber-based probes (organic and inorganic) employing high permeability contrast (nanometer and micrometer-diameter pores) and wettability stimulation (switching from hydrophilic to hydrophobic). The deliverables include a catalog of fundamental parameters and basic absorption and transport mechanisms analyzed through modeling and experiments, technological tricks and prototypes of materials and probing devices, documentation of research results, and engineering student educations. Involvement of the brightest high-school, undergraduate, and graduate students in modern surface and nanotechnology research is considered an important mission of this project. As the project progresses, we plan to develop new courses for graduate students and disseminate the results through many industrial partners.
