Molecular design is an optimization problem that seeks to find an optimum of some function (e.g. Gibbs free energy of binding) given a space of possible molecular structures (in the case, there is a surjective mapping between molecular structures and the set of aptamer ssDNA sequences, which may be non-injective). In this study, we explore an approach for designing an aptamer by searching for a maximum geometric complementarity of interacting molecular interfaces across a library of 3D molecular models for ssDNA sequences and a human insulin. The latter is readily available from pharmacies, as it's an important human protein. ssDNA for aptamer could also be readily synthesized by numerous providers of oligonucleotide synthesis companies. Together, this simplifies the experimental verification and make it a good model system for studying aptamer-protein interactions. In general, a good aptamer that binds with a high affinity should satisfy these two criteria, that are mere consequences of the fundamental equation of thermodynamics: