Saint Vincent Saint Mary's High School 1 article published in JoVE Bioengineering Characteristics of Precipitation-formed Polyethylene Glycol Microgels Are Controlled by Molecular Weight of Reactants Susan Thompson1, Jessica Stukel1, Abrar AlNiemi1,2, Rebecca Kuntz Willits1 1Department of Biomedical Engineering, The University of Akron, 2 This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Increasing the PEG molecular weight increased microgel diameter and swelling ratio. Simple adaptations to the PEG microgel precipitation reaction are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds.