Patterned Electrospinning

The Challenge

Gossamer Spacecraft are lightweight, large-scale, deployable spacecraft that will enable revolutionary, light-gathering and transmitting capabilities for solar sails, telescopes, power collection and communications.

Thinner films are lighter in weight and therefore more desirable. But theyÕre also more prone to tearing during handling, deployment and use (i.e. from micrometeorite impacts).

The Materials Technology Group at PSI is currently developing a process for the rip-stop reinforcement of ultra-thin, or Gossamer, polymer films with polymer nanofibers.

PSI is teamed with a world leader in the manufacture of space durable thin films, SRS Technologies (Huntsville, AL).

The PSI Process

The Materials Technology Group has developed and is patenting a process called Patterned Electrospinning, which is used to produce and deposit the polymer nanofiber reinforcement on ultrathin films supplied by SRS. Mechanical properties measurements have shown a nanofiber reinforced polymer film, 7 microns thick, to have the same tear resistance as a film 4 times its thickness and equivalent in weight.

Samples provided to SRS for evaluation were confirmed to be highly tear resistant, but they complained the reinforcement itself was poorly robust. A tear propagating through the reinforced film is shown at right, the white lines are the reinforcement.

The Materials Technology Group has developed high precision inkjet printing of non-aqueous solvents for a program using electrochromic polymers. The inkjet printing method was adapted for the Òsolvent weldingÓ of the nanofiber ripstop reinforcement.

This Òspot weldedÓ ripstop reinforcement is shown in the 20X microscope image at right. The white reinforcement strip is 1.3 mm wide and the solvent drops welds are 0.2 mm in diameter. The nanofibers, at 400 nm diameter, are difficult to resolve in this image. The addition of the solvent weld has significantly enhanced the robustness of the nanofiber reinforcement.

The Result

SRS and PSI are both under contract to NASA Langley Research Center for the development of enabling Gossamer film technologies. NASA has requested that a 10 m by 10 m solar sail be constructed using the SRS thin film and PSI ripstop technologies. SRS will provide 2.5 micron thick polymer film and PSI will apply the rip stop reinforcement to the film. This small scale manufacturing effort may lead the way for SRS to potentially license the PSI nanofiber and inkjet technology for Gossamer film manufacture.