Honors College

Document Type

Honors Thesis


Biomedical Engineering


Karissa Tilbury

Committee Members

Scott Collins, Andre Khalil, Melissa Ladenheim, Michael Mason

Graduation Year

May 2021

Publication Date

Spring 5-2021


The University of Maine is one of the world’s leading producers of cellulose nanofibers (CNF). This material has the power to revitalize the Maine paper industry. This has led to an abundance of labs on campus researching applications for the material. Active research activities at the University of Maine include industrial applications such as filtration, biodegradable packaging, building materials and niche health care applications. Niche health care applications include wicking pads for point of care diagnostics and tunable biomaterials ranging from dressings to implantable bone-like materials. Medical applications require an analysis of the biocompatibility of CNF.CNF is biocompatible in general: however, the degree of biocompatibility, particularly for tissue engineering applications involving long term integration within the body, is an area of active research. CNF is a highly tunable biomaterial; control of the fibril anisotropy dramatically alters bulk biomechanical properties which also modulates biological interaction. To tune fiber anisotropy, a novel strategy to produce single direction-oriented CNF films by application of a unilateral force via a latex substrate was developed. The alignment of CNF films was characterized using both polarized light microscopy and scanning electron microscopy(SEM). CNF is birefringent; therefore, using polarized light microscopy the alignment of CNF can be inferred by quantifying the birefringence optical index (BOI). The BOI ranges from -1 to 1, with high birefringence found at the extrema values. To validate the birefringence orientation sensitivity to CNF film alignment; we performed SEM for direct assessment of fiber alignment using OrientationJ, a FIJI plugin. Hydroxyapatite (HA) was incorporated as an additive to evaluate the application of this method to cellulose nano composites. Both the BOI and the SEM fibril analysis confirmed that CNF fibrils are aligned preferentially along the axis of force transmission. Furthermore, the addition of HA did not diminish the degree of CNF fibril alignment. Overall, we demonstrate a rapid and economic approach to fabricate and assess fibril alignment in CNF films useful for a myriad of tissue engineering applications.