Abstract: This document relates to two dimensional (2D) protein arrays can be used in biotechnology applications, as well as methods of making and using 2D protein arrays. In some cases, a 2D protein array can be used to evaluate (e.g., image) a structure (e.g., a three dimensional (3D) structure) of a protein of interest. In some cases, a 2D protein array can be used to evaluate (e.g., characterize) protein-protein interactions (e.g., stable interactions vs. transient interactions). In some cases, a 2D protein array can be used to evaluate a binding domain in a protein of interest. In some cases, a 2D protein array can be used to evaluate (e.g., identify) binding targets and/or partners of a protein of interest.