Table 1.
Growing robots.
| Environment | Max.growth | Dimension (cm) | Properties | Binding mechanism | Energy | Role of growth | Dev. level | Task |
|---|---|---|---|---|---|---|---|---|
| MOLECULE-INSPIRED ROBOTS | ||||||||
| Griffith, 2004; Griffith et al., 2005—random parts | ||||||||
| Floating table | 30 modules | 5 × 5 × 1.5 | SA; SR | McE | OB | Replication | PoC | Structure |
| White et al., 2004—stochastic self-reconfigurable robots 2D—Figure 2A | ||||||||
| Floating table | 3 modules | 6 × 6 base | SA; SC | Em | EP | Assembly | PoC | Structure |
| White et al., 2005—stochastic self-reconfigurable robots 3D—Figure 2B | ||||||||
| Tank with fluid | 2 modules | 10 × 10 × 10 | SA; SC | Em; Ff | EP | Assembly | PoC | Structure |
| Haghighat et al., 2016—lily robots—Figure 2C | ||||||||
| Fluidic surface | 6 modules | 5 × 5 × 2.5 | SA | Em | OB | Assembly | PoC | Structure |
| CELL-INSPIRED ROBOTS | ||||||||
| Fukuda and Nakagawa, 1988; Fukuda and Nakagawa, 1990—CEBOT (Mark II)—Figure 3A | ||||||||
| Ground | 2 modules | 9 × 18 × 5 | SA | McU | EP | Assembly | Partiala | Manipulation |
| Yim et al., 2000; Yim et al., 2002—PolyBot—Figure 3B | ||||||||
| Ground | 6 modules arm adding 1 module | 6 × 7 × 11 | SA; SC | McPHsma | EP | Assembly | Operative | Locomotion |
| Payne et al., 2004; Rubenstein et al., 2004—CONRO—Figure 3C | ||||||||
| Ground | 2 modulesb | 10.8 × 4.4 × 4.5 | SA; SC | McPHsma | OB | Assembly | Operative | Locomotion |
| Murata et al., 2006; Kurokawa et al., 2008—M-TRAN—Figure 3D | ||||||||
| Ground | 17 stationary modules + 3 moving modules | 6.5 × 13 × 6.5 | SA; SC | McU | OB | Assembly | Operative | Locomotion |
| Yim et al., 2007—CKbotc—Figure 3E | ||||||||
| Ground | 3 clusters of 5 modules | Not specified | SA; SC | Mg | OB | Assembly | Operative | Locomotion |
| Wei et al., 2011—Sambot—Figure 3F | ||||||||
| Ground | 2 modules | 8 × 8 × 10.2 | SA; SC | McU | OB | Assembly | Operative | Locomotion |
| Davey et al., 2012—SMORES—Figure 3G | ||||||||
| Ground | 2 modules | 10 × 10 × 9 | SA; SC | Mg | OB | Assembly | Partiald | Locomotion |
| Romanishin et al., 2013—M-Blocks—Figure 3H | ||||||||
| Ground | 1 module assembles to a group | 5 × 5 × 5 | SA; SC | Mg | OB | Assembly | Operativee | Locomotion |
| Qiao et al., 2014—modular self-reconfigurable robot—Figure 3I | ||||||||
| Ground | 4 modulesf | 26.4 × 7.1 × 6.5 | SA; SC | McPH | OB | Assembly | Operative | Locomotion |
| Spröwitz et al., 2014—Roombots—Figure 3J | ||||||||
| Ground | 4 modulesg | 11 × 11 × 22 | SA; SC | McU | OB | Assembly | Operative | Furniture building |
| ORGANISM-INSPIRED ROBOTS | ||||||||
| Sadeghi et al., 2017—plant-root-like robot growing with 3D printing—Figure 4A | ||||||||
| Subsoil | 140 mm | 5Ø × 6.3Lh | SB | FDM | EP | Locomotion | Operative | Soil penetration in multi directions |
| Hawkes et al., 2017—soft robot growing with inflation mechanism—Figure 4B | ||||||||
| Ground/air | 70 m | 4.8Øi | E | IM | EP | Locomotion | Operative | Ground navigation |
Environment represents the operative location of the robot. Max. growth is the maximal growth shown in papers; it represents the maximal number of modules performing assembling or the maximal length of elongation. Dimension is the single module size. Properties: SA, self-assembly; SR, self-replication; SC, self-reconfiguration; SB, self-building structure; E, extension. Binding mechanism: McE, mechanical latch, regulated electromagnetically; McU, mechanical hooks; Em, electromagnets; Mg, magnets; Ff, pressure of fluid flow; McPHsma, mechanical pin-hole and SMA; McPH, pin-hole connector; LL, alignment of layer by layer filament; FDM, fused deposition modeling; IM, inflation mechanism. Energy: OB, on board; EP, external power. Role of growth defines for which functionality a growing process is used. Level of development of the system with respect to the growing process: simple proof of concept (PoC) of growth, partial, or operative. Task describes for which operation the robot has been developed (Structure means structure formation).
aThe system was modeled for manipulation tasks in industrial environments. The authors achieved the deployment of three modules demonstrating self-assembly with two. Manipulation was not demonstrated.
bModules need to stay in the proximal distance.
cAn evolution of the earlier PolyBot robot.
dThe authors show self-assembling, self-reconfiguration, and lifting of a module with two modules.
eCrawling is achieved for a group of modules.
fSelf-assembling is essential for reconfiguration, the authors show the assembling of 1 module and then of 2 distinct modules to a cluster of 2 modules.
gThe authors show the assembling of 2 clusters of 2 modules to overcome a convex edge module.
hLength of the apical module.
iDiameter used to obtain the maximal length of 70 m.