Microenvironmental biophysical stimuli influence diverse cellular functions, such as directional motility and stem cell differentiation. Previously, researchers have tuned the linear stiffness of microposts to investigate cell mechanobiological processes and direct cellular behavior; however, microposts suffer from an inherent, yet critical drawback -regulation of micropost stiffness is fundamentally limited to "bi-axial" control. To overcome this issue, here we utilize three-dimensional (3D)

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... rect-write laser lithography processes to fabricate arrays of microscale springs (µSprings). By adjusting the geometric characteristics of individual µSprings, the x-, y-, and z-axis stiffness of the cellular substrate can be customized at the microscale. COMSOL simulations were performed to characterize the theoretical "tri-axial" stiffness associated with a variety of µSpring designs. Endothelial cells seeded on µSpring arrays were found to successfully deform the µSprings via cell-generated forces. By enabling user-control over the tri-axial stiffness of discrete, microscale substrate features, the presented µSpring methodology could offer a powerful platform for cellular studies and applications in fields including tissue engineering, biomaterials, and regenerative medicine.