Just imagine, you have a canvas and only black as a painting colour. What could you represent? Sure a lot. Now you hav all greyscales on your disposal. By which extent you would increase your espression capabilities? Hugely.
The engineer who chooses a conventional design for a mechanism can just use two extremes: the members as ideally rigid components and the rolling or sliding interfaces in the bearings as ideally yielding components. Of course, in reality, members are not infinitely stiff and bearings in their kinematic behavior not perfect. But all this is of no advantage to the engineer. Quite the contrary: he fights against it, since members are not allowed to deform and bearings should not need forces to move. On the contrary, the engineer adopting the option of solid-state kinematics has the whole range in front of him: he distributes load-carrying capabilities and flexibility exactly dosed in theplaces where it is needed. In this way he can do much more for the performance of his end product. In the optimisation language we say that the design of compliant systems tooks place in incomparably larger design spaces. It is therefore possible to fulfill desires and requirements (in a single or combined way) in a way which is not even thinkable for a conventional technique.
One of the dreams which get closer is the realisation of solid-state mechanisms. Lightweight structures (like an airplane wing or fuselage) base on thin-walled components and avoid load concentrations. Conventional mechanisms lives from full cross sections and localised loads. In conventional bearings, loads are transmitted as point or line forces. Due to this reason, the load-carrying material is used sub-optimally, which, in turn, leads to unfavourable load-to-weight ratios. The situation is different for compliant systems, which bear external load always by mean of surface forces and therefore to distributed stresses in the hinges. Compliant systems are therefore lightweight compatible.
How close to another lightweight structures and compliant systems are can be seen, for example, in the similar architecture: both are finely structured and hierarchically organized, while in conventional mechanisms usually compact elements with simple geometry can be encountered.
The lightweight capabilities of compliant mechanisms can be even seen in simple applications: compliant replacements of existing, conventional mechanisms and assemblies perform much besser than their classic counterparts, as far as weight is concerned (for the same load-bearing capacity). But solid-state kinematics offers much more than this to lightweight design: It is the key technology for a dream which is centuries old: the biomimetic wing.