We describe a method of fabrication of nanoporous flexible probes which work as artificial proboscises. The challenge of making probes with fast absorption rates and good retention capacity was addressed theoretically and experimentally. This work shows that the probe should possess two levels of pore hierarchy: nanopores are needed to enhance the capillary action and micrometer pores are required to speed up fluid transport. The model of controlled fluid absorption was verified in experiments. We also demonstrated that the artificial proboscises can be remotely controlled by electric or magnetic fields. Using an artificial proboscis, one can approach a drop of hazardous liquid, absorb it and safely deliver it to an analytical device. With these materials, the paradigm of a stationary microfluidic platform can be shifted to the flexible structures that would allow one to pack multiple microfluidic sensors into a single fiber.

There was an error published in J. Exp. Biol. 217, 2130-2138. Eqns A12 and A13 in the Appendix were cropped. The online pdf and fulltext versions (but not the print version) of the article have been corrected. The correct versions of the equations also appear below.We apologise to the authors and readers for this error. ABSTRACT Fluid-feeding Lepidoptera use an elongated proboscis, conventionally modeled as a drinking straw, to feed from pools and films of liquid. Using the monarch butterfly, Danaus plexippus (Linnaeus), we show that the inherent structural features of the lepidopteran proboscis contradict the basic assumptions of the drinking-straw model. By experimentally characterizing permeability and flow in the proboscis, we show that tapering of the food canal in the drinking region increases resistance, significantly hindering the flow of fluid. The calculated pressure differential required for a suction pump to support flow along the entire proboscis is greater than 1 atm (~101 kPa) when the butterfly feeds from a pool of liquid. We suggest that behavioral strategies employed by butterflies and moths can resolve this paradoxical pressure anomaly. Butterflies can alter the taper, the interlegular spacing and the terminal opening of the food canal, thereby controlling fluid entry and flow, by splaying the galeal tips apart, sliding the galeae along one another, pulsing hemolymph into each galeal lumen, and pressing the proboscis against a substrate. Thus, although physical construction of the proboscis limits its mechanical capabilities, its functionality can be modified and enhanced by behavioral strategies.

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We developed a novel technique enabling determination of the permeability of electrospun yarns composed of hundreds of fibers. Analyzing the wicking kinetics in a yarn-in-a-tube composite conduit, it was found that the kinetic is very specific. The liquid was pulled by the capillary pressure associated with the meniscus in the tube while the main resistance comes from the yarn. Therefore, one can separate the yarn permeability from the capillary pressure, which cannot be done in wicking experiments with single yarns. A surface tensiometer (Cahn) was employed to collect the data on wicking kinetics of hexadecane into the yarn-in-a-tube conduits. Yarns from different polymers and blends were electrospun and characterized using the proposed protocol. We showed that the permeability of electrospun yarns can be varied in a broad range from 10(-14) m(2) to 10(-12) m(2) by changing the fiber diameter and packing density. These results offer new applications of electrospun yarns as flexible micro- and nanofluidic systems.