**2.2. Flexible fluidic structural elements**

Flexible fluidic structural elements complete the biomimetic approach. There are many examples of hydrostatic skeletons in nature [130].

Inflatable structures are well known in fields of crisis intervention [26] and exhibition stand construction [94]. Other applications include space structures like antennas [33, 79, 82, 132] and rovers [28, 48, 63, 72].

Most robotic designs with inflatable structures aim at space applications since they have a small shipping volume when deflated. Koren et al. [72] proposed a design for zero gravity applications and operating pressures of about 3.5 *bar* (figure 9(c)). Shoham et al. [104, 105, 118] developed a inflatable robot as shown in figures 9(a) and 9(b). They also characterized the robot regarding its stiffness at internal pressures up to 2 *bar*.

**Figure 9.** Different Robots with Inflatable Structures

The works of Sanan et al. [106], Maruyama et al. [83], and Voisemebert et al. [135] focus more on service and inspection robotics. Operating pressures are in the range of 0.4 − 0.6 *bar*. The 1-DOF arm developed by Sanan is shown in figure 9(d).
