Highly flexible structures (springs) can be found in many precise devices, such as small actuators of optical disc drive and mobile cameras. A good configuration design is crucial for correct operation of these devices. In this case, optimization techniques can be applied to design of these flexible structures, aiming to reduce development time and costs. Remarkably, the design of these structures turns out to be a challenge in topology optimization. Thus, in this work, a formulation for designing highly flexible structures by using topology optimization is investigated. The topology optimization problem is defined as minimization of the mean compliance subjected to material volume and perimeter constraints, combined with a projection technique. The material model is based on the traditional SIMP approach and the optimization problem is implemented by using COMSOL software and solved by using MMA algorithm. A well-known plane string case has been carried out to evaluate the potential of the proposed topology optimization formulation.