NSF Org:	CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems
Recipient:	THE LELAND STANFORD JUNIOR UNIVERSITY
Initial Amendment Date:	January 23, 2024
Latest Amendment Date:	January 23, 2024
Award Number:	2400010
Award Instrument:	Standard Grant
Program Manager:	Rohit Ramachandran rramacha@nsf.gov  (703)292-7258 CBET  Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG  Directorate for Engineering
Start Date:	April 1, 2024
End Date:	March 31, 2027 (Estimated)
Total Intended Award Amount:	$391,345.00
Total Awarded Amount to Date:	$391,345.00
Funds Obligated to Date:	FY 2024 = $391,345.00
History of Investigator:	Danielle Mai (Principal Investigator) djmai@stanford.edu Daniel Congreve (Co-Principal Investigator)
Recipient Sponsored Research Office:	Stanford University 450 JANE STANFORD WAY STANFORD CA  US  94305-2004 (650)723-2300
Sponsor Congressional District:	16
Primary Place of Performance:	Stanford University 450 JANE STANFORD WAY STANFORD CA  US  94305-2004
Primary Place of Performance Congressional District:	16
Unique Entity Identifier (UEI):	HJD6G4D6TJY5
Parent UEI:
NSF Program(s):	Proc Sys, Reac Eng & Mol Therm
Primary Program Source:	01002425DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):
Program Element Code(s):	140300
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.041

ABSTRACT

This research seeks to improve the sustainability of plastics manufacturing by introducing new recycling mechanisms into 3D-printing materials. Currently, over 30% of 3D-printed materials are discarded immediately after printing, motivating a vision of the future where 3D-printing scraps are recycled at the point of production. This research will drive a transition from a linear economy of ?print-to-landfill? to a circular economy of ?print?recycle?reprint.? To achieve this transition, novel optical recycling technologies for on-demand regeneration of 3D-printing resins are proposed. Building on recent discoveries by the research team, this project combines reversible photochemistry and nanotechnology based light delivery mechanisms to demonstrate the optical recycling of 3D-printing resins. Optically recyclable resins have potential to transform plastics processing beyond 3D printing by providing low-energy, on-demand options to regenerate chemically active polymer resins that can be reused over numerous cycles. Establishing design rules for photoresponsive polymers will further advance large-format and high-resolution patterning for applications in semiconductors, optoelectronics, and biological scaffold materials. To broaden participation in research, the PIs will recruit and train researchers from underrepresented populations including women, first-generation and low-income (FLI) students, and underrepresented minorities (URMs). Research findings will be integrated into engineering coursework, emphasizing inquiry-based approaches that will engage students in the real-world challenge of sustainable plastics manufacturing. Finally, concepts in sustainability and additive manufacturing will be explained through educational coloring book pages and ?no jargon? research highlights. Educational content will be distributed to the broader public online and at K-8 outreach events across the San Francisco Bay Area.

The long-term goal of this research is to reduce plastic waste from 3D printing processes by engineering reusable resins that can be printed, ?erased,? and re-printed over numerous cycles. The objective of this proposal is to engineer robust, modular mechanisms for optical recycling into polymer resins for 3D printing. Engineered resins comprise multi-arm polyethylene glycol with photoresponsive anthracene end groups (PEG-anthracene) and UV-emitting upconversion nanocapsules. PEG-anthracene undergoes reversible photocoupling reactions in response to different wavelengths of UV light; these reactions drive polymerization and depolymerization of PEG-anthracene networks. UV-emitting upconversion nanocapsules are activated by low-energy visible light that penetrates deeper into materials than UV light; these nanocapsules will deliver UV light needed to depolymerize 3D-printed materials. Aim 1 of this research plan will quantify the influence of polymer structure on photo-polymerization and depolymerization reaction kinetics using in situ dynamic rheology measurements and a reaction-diffusion model. It is hypothesized that polymers with fewer, shorter arms will be more amenable to optical recycling due to faster depolymerization into smaller components and lower solution viscosities. Aim 2 will identify the chemical principles underlying the stability of upconversion nanomaterials. Encapsulation screening studies will determine the core solvent and surface ligand requirements for robust stabilization of UV-emitting nanocapsules. Aim 3 will establish design rules to improve the modularity of optically recyclable polymer resins. The adoption of violet-activated photocoupling reactions will enable facile integration of next-generation resins into modern 3D printers. This work will leverage complementary expertise of the PIs in polymer engineering, rheology, optical nanomaterials, and additive manufacturing. Broader impacts from this research will include the development of new polymer processing and recycling technologies, research training and mentorship at the undergraduate and graduate levels, and deployment of educational and outreach content about plastic recycling and optical technologies.

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.

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