# In-Plane Material Handling: A Systematic Review
## 3 Results
### Answer to RQ1
However, for these applications, pneumatic surfaces still employ MEMS-based hardware, as seen in [17], to direct and control the air jets. On the other hand, such platforms exploit coils and magnets to achieve very precise positioning and feeding. Vibrating solutions have been proposed that use a saw-tooth vibrating surface [49; 50] or a smooth surface [29] to rearrange parts' positions and orientations. Moreover, a ciliary device was utilized for micro-displacements, employing rotating eccentric masses to replicate a specific cilia bio-inspired movement of the _P. caudatum_ organism [36]. Moving to macroscopic transport, the initial rotor solution proposed by [PERSON] et al. [31] was subsequently explored in numerous other studies over the years, including those by [PERSON] et al. [52], [PERSON] et al. [53], [PERSON] et al. [3], and [PERSON] et al. [4]. Additionally, distributed in-plane manipulation of macroscopic parts has been introduced into other technologies, such as novel pneumatic systems [33; 54; 55; 56], variable-morphology surfaces [37; 57; 58; 59; 60], mobile platforms [61; 62; 63], vibrating surfaces [20; 28], and ciliary surfaces [11; 64]. These new solutions aim to improve handling skills and surface control capabilities. Based on the literature research and identification of the size of material and handling speed as key parameters for the effectiveness of macroscopic transport, the rotor solution is recognized as the most effective. These designs employ different modules and a variable number of wheels, along with a camera, to manipulate packages. Specifically, [PERSON] et al. [52] and [PERSON] et al. [53] suggested the use of one swiveling rotor with an integrated spin drive per module. The device proposed in [3], which is currently used in industrial applications under the name _Cellveyor_, includes three fixed wheels per module with axes oriented at 120\({}^{\circ}\) and controllable speeds to direct the total friction force (Figure 4c). Meanwhile, [PERSON] et al. [4] used even more wheels, alternating between modules with five and seven wheels, all actuated to move objects placed on top. Regarding pneumatic surfaces for macroscopic material transport and manipulation, as outlined in [56], there are two main types, namely air-flow manipulators and air-jet manipulators. Air-flow technology uses pressure fields to move and orient parts, while air-jet technology employs directed air jets to push an object supported by an air bearing [56]. For the first technologies, two different examples of pressure field generation are provided. The first, as proposed in [54; 55], uses an array of modules capable of blowing or sucking air, and the second, as proposed in [33; 56], utilizes an extensive air cushion capable of creating local air sinks. Proceeding with variable-morphology surfaces, several solutions to manipulate light and small objects have been studied. [PERSON] and [PERSON] [57] first introduced a \"Magic carpet\" design (Figure 5b), i.e., a grid of vertical linear actuators used to create unevenness in the surface and move parts with them, followed several years later by the solutions proposed in [58; 60]. In contrast, instead of simple vertical cylindrical actuators, [PERSON] et al. [58], employed soft ones with variable stiffness, while [PERSON] et al. [60] connected the vertices of the actuators with planes to achieve a continuous surface. Other interesting proposals include studies such as [37; 59; 65; 66; 67], where a caterpillar-inspired table was examined for object manipulation, and the work reported in [68], which explored the use of a deformable sheet containing ferrofluid to convey parts through its ripples. Conversely, the mobile platforms studied for macroscopic handling, unlike microscopic ones, can not only carry an object on top, as in [61], but also around, as in [62; 63; 69], with small robot platforms surrounding the part to complete handling. Lastly, vibrating and ciliary systems for macroscopic motion have evolved similarly to their microscopic counterparts.