Vibration energy harvesters can help in different areas. These vary from supplying power to medical implants or wireless sensors that can aid in predicting natural disasters. However, the problem is that they are not able to generate power across a large bandwidth of frequencies. Bistable energy harvesters can solve this problem when these are able to oscillate between their stable equilibria. A bistable mechanism that has these benefits is a post-buckled beam. However, a potential energy barrier needs to be overcome before this interwell motion can occur. If there is no interwell motion, the power output will be severely reduced. A topology optimization is performed on a beam so that the buckling loads approach almost equality. This leads to lowering of the potential barrier and thus interwell motion is eased. Numerical simulations and experimental measurements show that the stiffness can be reduced by a factor of 10 by removing material. Another topology optimization is performed to increase the stiffness. It has been numerically and experimentally verified that removing material can increase the stiffness of the post-buckled beam by 20%.