EAGER: In-Situ Continuous Filler Sintering via Intense Pulsed Light in DLP 3D Printing Toward Efficient Composite Electrodes

This EArly-concept Grant for Exploratory Research (EAGER) project funds research that aims to advance the fundamental understanding of a hybridized 3D-printing approach that has significant application potential, such as in composite electrodes. Current 3D printing methods such as stereolithography and digital light processing (DLP) can manufacture freeform polymer matrix composites with randomly oriented heterogeneous fillers or fibers, but they have not been studied for creating connected and continuous fiber composite structures.

Continuous fiber composites in industry are utilized for enhancing strength and toughness, as well as for imparting certain thermal, electrical, or ionic transport functionalities into a polymer matrix composite. Continuous filler composites are typically made via molding techniques with significant manual effort. There is an urgent need for further scientific exploration in utilizing continuous fillers to maximize electrical and thermal performance and efficiency in freeform fabricated polymer matrix composites.

The approach investigated in this project combines multiple manufacturing principles: acoustic manipulation (via acoustophoresis) to agglomerate and align discrete particles in a polymer vat, photopolymerization (via DLP) to define the geometry of the component in each layer, and photonic sintering (via intense pulsed light sintering, IPLS) to create connected and fused fibers from the particles aligned through acoustic manipulation. Successful completion of the project looks to enable a new freeform manufacturing approach for heterogeneous materials, and the approach could be extended to include other fillers such as piezoelectric materials or ionically conductive materials to realize advanced functionalities.

Apart from acoustophoresis for particle alignment, DLP printing and IPLS have not been explored as an integrated process due to their significant processing differences. Their joint effect on the process performance is not well understood. While IPLS utilizes high energy dosages (J/cm2 - kJ/cm2) and broad wavelength spectral distribution during illumination, DLP printing, meanwhile, utilizes relatively low energy (mJ/cm2) and a very narrow wavelength spectral distribution to induce polymerization of the intended geometry.

This EAGER research project explores their joint effect to synergistically process two heterogeneous material types: polymer resin (low temperature processing, low light energy) and metal (locally high temperature processing, high light energy). To combine DLP printing and IPLS, photopolymerization will be induced via red light illumination, with IPLS being performed via UV/Blue light illumination.

Additionally fundamental relationships look to be established between acoustic stimulus (frequency, amplitude, duration), embedded particle properties (size, concentration within resin, and shape), and would-be sintered fiber dimensions (width, height, spacing).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.