## 2 Pressurization Mechanisms
### Prototypes Using Inflated Air Bags  
To identify which shape of air bag performed best as a pressurization mechanism, we conducted a series of tests (Tests No. 1-3) as shown in Figure 6. Test No. 1 acted as an observatory test without using any air bag (see Figure 6a,b). In all tests, two parallel plates used for compression were loaded with dead weight to exert a constant force. A drip bag and air bags were filled with air. The air was released from the drip bag at a low flow rate controlled by a valve, while the air in the air bag was trapped by closing the valve. Pressures in the drip bag and the air bag were measured simultaneously. Test No. 1 showed the steady decreasing of the drip bag pressure that was normalized by the initial drip bag pressure, though under a constant force from the dead weight (see Figure 7a). This may have been due to the change of contact surface area between the plate and the drip bag as the drip bag deflated. The pressure value in the ordinate in Figure 7b,c was normalized by the initial air bag pressure. At the starting point in Test  
Figure 4: Prototype MOVE-ROLLER. (**a**) Squeezing mechanism on a drip bag by a pair of rollers. (**b**) Operational testing of the mechanism. (**c**) Observation of drip fluid escape. (**d**) Schematic explanation of the drip fluid leakage occurring inside the drip bag. No. 2, the drip bag pressure was higher than the air bag pressure (see Figure 7b). This may be attributed to the surface tension occurring at both the curving (arc-like) side-surfaces of the drip bag which were not in contact with the air bags [55]. However, this did not happen in Test No. 3, in which the side-surfaces of the enwrapped drip bag were in contact with the sleeping-bag-shaped air bag (see Figure 7c). In both Tests No. 2 and No. 3, it can be observed that the air bag pressure decreased slightly due to the change of contact surface area with the plates as the air bags compressed the drip bag. Seeing that the pressures of both drip bag and air bag showed the best unison in Test No.3 (see Figure 7c), we concluded that the sleeping-bag-shaped air bag (see Figure 6e) was the best inflating mechanism to pressurize the drip bag. Figure 5: Prototype FIX-ROLLER. (**a**) A vacuum piston cylinder, whose actual orientation (vertical position) is shown in (**c**), pulls and rotates a rolling mechanism by a wire. (**b**) An exterior view of the prototype. (**c**) An interior view of the prototype mounted with a drip bag. (**d**) The rolling mechanism is locked at the standby position by an interior-mounted rachet gear tooth (not visible in (**c**)). The rolling mechanism is unlocked by turning a toggle switch at the exterior side panel. (**e**) The rolling mechanism is reset to the standby position using a hexagonal wrench. Figure 6: (**a,b**): Test No. 1. A drip bag is placed between parallel plates with no air bag in (**a**), and then loaded with dead weight in (**b**). (**c,d**): Test No. 2. Two pillow-shaped air bags are placed between the parallel plates in (**c**), then a drip bag is inserted in between the two air bags, and the sandwiched drip bag is loaded with dead weight in (**d**). (**e,f**): Test No. 3. A drip bag is enwrapped in a sleeping-bag-shaped air bag in (**e**), and then loaded with dead weight in (**f**). A prototype (hereafter, AIR-BAG) using the sleeping-bag-shaped air bag as the pressurizing mechanism was then developed (see Figure 8). To inflate the air bag, we designed a novel air-compressor mechanism that was driven by a vacuum piston cylinder. As shown in Figure 8a, a small piston with a cross-sectional area of \(a_{S}\) in a vacuum piston cylinder (upper cylinder) pushes a large piston with a cross-sectional area of \(a_{L}\) through a connecting rod in an air piston cylinder (bottom cylinder), resulting in compressed air being supplied to an inflating air bag enwrapping a drip bag.