Flexible Fiber-based Micro and Nanofluidics for Probing Liquids

A fluidic probe comprising a plurality of oriented fibers with individual fibers having nano-pores in the fiber bodies, the oriented fibers being twisted together, wherein the twisted oriented fibers form micro-pores between the individual fibers, is disclosed. The fluidic probe exhibits excellent flexibility, deployability and absorptive capacity. The enhanced absorptive capacity is due to the fluid absorption via capillary action of the nano-pores and fluid transport via the micro-pores. The probes can also be formed so as to be remotely controlled by electromagnetic fields and thus be used in a hands-free fashion. With these probes, the paradigm of a stationary microfluidic platform can be shifted to include flexible structures that can include multiple microfluidic sensors in a single fibrous probe

Fully magnetic printing by generation of magnetic droplets on demand with a coilgun

In this paper, we exhibit a coilgun-based approach to drop-on-demand printing of liquids laden with magnetic particles. In contrast to other drop-on-demand technologies designed to print droplets only in gaseous environments, this methodology allows one to print magnetic droplets inside any gaseous or liquid media using the same coilgun. Furthermore, we demonstrate the basic principles of magnetic drop-on-demand generation and show the physico-chemical parameters controlling the process

Characterization of Permeability of Electrospun Yarns

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 m² to 10^–12 m² by changing the fiber diameter and packing density. These results offer new applications of electrospun yarns as flexible micro- and nanofluidic systems

Collective rotation of nanorods in thin films

In recent years, magnetic nanorods have caught great attention due to their unique features appealing to composite, medical, sensoric, optofluidic, and microrheology applications. In composite manufacturing, when the curing carrier has a time-dependent rheology, the alignment kinetics significantly depends on the processing time and rheological properties of the carrier. We study the kinetics of ordering of an assemble of nanorods suspended in a liquid with time-increasing viscosity. We introduce an orientational distribution function of nanorods and theoretically study the kinetics of nanorod ordering. Different regimes of ordering are revealed and classified. When the liquid solidifies exponentially fast, we show that the nanorods would not always align with the external magnetic field. Some nanorods could be frozen halfway to their equilibrium orientation parallel to the external field. The orientational distribution function of nanorods was analyzed by studying nanorod alignment in evaporating gels. The dark field optical microscopy was employed. Preliminary experimental data support the theory

Pressure distribution analysis from Effect of curvature on wetting and dewetting of proboscises of butterflies and moths

The code used to analyze the pressure distribution and plot the result

Supplementary material from Effect of curvature on wetting and dewetting of proboscises of butterflies and moths

Proboscises of butterflies are modelled as elliptical hollow fibres that can be bent into coils. The behaviour of coating films on such complex fibres is investigated to explain the remarkable ability of these insects to control liquid collection after dipping the proboscis into a flower or pressing and mopping it over a food source. By using a thin-film approximation with the air–liquid interface positioned almost parallel to the fibre surface, capillary pressure was estimated from the profile of the fibre surfaces supporting the films. The film is always unstable and the proboscis shape and movements have adaptive value in collecting fluid: coiling and bending of proboscises of butterflies and moths facilitate fluid collection. Some practical applications of this effect are discussed with regard to fibre engineering

Supplementary material from Effect of curvature on wetting and dewetting of proboscises of butterflies and moths

Proboscises of butterflies are modelled as elliptical hollow fibres that can be bent into coils. The behaviour of coating films on such complex fibres is investigated to explain the remarkable ability of these insects to control liquid collection after dipping the proboscis into a flower or pressing and mopping it over a food source. By using a thin-film approximation with the air–liquid interface positioned almost parallel to the fibre surface, capillary pressure was estimated from the profile of the fibre surfaces supporting the films. The film is always unstable and the proboscis shape and movements have adaptive value in collecting fluid: coiling and bending of proboscises of butterflies and moths facilitate fluid collection. Some practical applications of this effect are discussed with regard to fibre engineering

Critical pressure calculation from Effect of curvature on wetting and dewetting of proboscises of butterflies and moths

The code used to calculate the critical pressures specified in Table 1