# In-Plane Material Handling: A Systematic Review
## 3 Results
### Answer to RQ2
In Figure 6, systems are grouped by their field of application. Particularly interesting are the cases of manufacturing and intralogistics, which appear most frequently. Biomedical applications are only related to ciliary systems and are, thus, omitted from the comparison. Regarding the \"research\" field, comparisons do not seem relevant, as the goal is greater knowledge rather than practical application. Starting with the manufacturing sector for microscopic objects, the included systems are MEMS, vibrating surfaces, mobile platforms, and pneumatic surfaces. As previously mentioned, these technologies do not compete at the same level, and among them, MEMS systems remain more prominent within the field of research. This technology, if used directly, due to its working principle, is particularly slow in movement [30] and, moreover, complex to realize and maintain [79]. Given this, to manipulate small, light, and flat surface components, e.g., silicon wafers or generally in microfactories, it is preferable to use pneumatic systems for contactless applications [30; 43; 94], vibrating surfaces for a less complicated design [79; 80], or mobile platforms for more precise positioning [10]. However, this does not preclude the employment of MEMS technology in the construction of other devices, such as the microscopic valves of pneumatic modules themselves [30]. When increasing the size of the handled materials (meso and macro scales), still within the manufacturing sector, for the feeding of non-delicate materials or their positioning when high precision is not required, vibrating surfaces [28; 81] and rotor surfaces [31] are most effective. Pneumatic surfaces are used when contact with the object must be avoided (e.g., if fragile, clean, or dangerous), as well as for precision positioning [43]. Meanwhile, mobile platforms for macroscopic applications predominantly utilize a swarm approach [62; 63] and can even move bodies with curved geometry, adapting by employing more or fewer collaborative modules depending on the object size. For intralogistics applications, the most commonly used technologies are pneumatic surfaces, variable-morphology surfaces, and rotor surfaces. Analysis of their behavior for one of the main intralogistics applications, i.e., the transport and handling of packages, is the subject of the last research question (RQ3). However, some general comparisons can be made here. These three technologies are distinguished by characteristics that determine their choice depending on the task at hand. Specifically, pneumatic solutions are the only ones suitable for contactless conveyance and feeding applications. They find outlets in the food industry, LCD industry, and solar cell manufacturing [43]. In some cases, even for delicate materials, soft variable-morphology surfaces can be indicated [59], generally for feeding tasks and especially sorting [60]. Their use in industry, even for non-soft versions, is not yet as widespread as the other two classes but is gradually increasing, since their application is not limited to bodies with flat geometry and rigid bodies [68]. Ultimately, rotor surfaces remain the preferred choice for all intralogistics activities involving non-delicate materials, both in terms of heavy weight and high volumes of transport [3; 8; 91]. Finally, Figure 6(a),b report the number of publications retrieved per technology class (Figure 6(a)) and their distribution over the years (Figure 6(b)). The purpose of these figures is to complete the bibliometric analysis started in Section 3.1 with the new information about the technology classification that was just collected. In summary, this subsection provides a comprehensive categorization of manipulative systems based on different technologies, addressing the second research question (RQ2). Through the classification of these devices according to their employed technology, transportable material characteristics, and field of application, insights into the diverse landscape of manipulative systems are presented.