Electrospinning Overview

AAI is the first company to use electrospinning to produce dry adhesives, which offers the potential for solvent-free, environmentally friendly adhesives that are strong when you need them, but can be easily removed from surfaces without leaving behind a residue or causing damage.produce nanofibers, can be used to produce dry adhesives.  Electrospinning is a versatile technique to fabricate nanofibers with finely controlled nanostructures that are useful for a range of properties, including adhesives.  Most importantly, electrospinning offers a scalable route to control these structures with a resolution that can typically only be achieved with much more time consuming, batch processes such as lithography.

Electrospinning occurs when the electrical forces at the surface of a polymer or adhesive solution overcome the surface tension and cause an electrically charged jet to be ejected.  The electric force accelerates and stretches the adhesive jet resulting in a decrease of the diameter and a concomitant increase in length.  The cross-sectional area of the adhesive jet decreases by a factor as large as a million, and vice versa in length.  The jet dries, solidifies and is deposited on a collecting plate.

Electrospinning creates high aspect ratio aligned fibers that, with the right dimensions and membrane compliance, conform to surface asperities, to make millions of contact links per unit of surface area.  These contacts enhance physical interactions such as vdW forces and capillary effects.

Due to the extremely small diameter of nanofibers produced with this approach, they can also present mechanical interlocks and behave as composite laminates.  The morphology of the nanoscale cylindrical solids is vastly different from previous work based on protruding carbon nanotubes, nano-forests and lithographically molded protruding micropillars.  The nanoscale mechanical interlocks present strong adhesion between mating faces that can be conceptualized as a nanoscale form of Velcro®-brand hook-and-look fasteners, except the interlocks arise from aligned nanofibers (nano-Velcro adhesives).  The nanoscale dry adhesive film thickness afforded by electrospinning cannot be otherwise produced economically using solid-state polymers at room temperatures with other manufacturing routes.

The key factor to AAI’s success is in the scalability of the electrospinning process.  There are already a large number of firms using electrospinning for various applications, in particular for the production of air filters and membranes.  A number of third-party manufacturing companies have also been established to prepare large quantities of electrospun materials for outside companies.  This third-party approach may be a viable first-step toward large-scale manufacturing for AAI, as this would allow for extensive product development and qualification from customers to be achieved before committing to the construction of a manufacturing facility by AAI or the design of an integrated process line at an AAI customer facility.  The most important consideration here is the morphology of the adhesive films.  For a single-component approach, such as with nylon nanofibers, the fibers must be extremely small diameter, which requires a very low solution concentration and slow deposition rates, and the degree of alignment must be high to maximize contact area and prevent any voids that may nucleate crack growth and limit strength.