Fabrication and Untethered Actuation of Soft Robotics with Miniature Piezoelectric Pump System

Soft robotics provide great possibilities to break the gap between robots and 
humans. It is believed to work with humans or even in the human bodies thus the 
demand of portability, safety, and autonomy of soft actuators need to be fulfilled. Fluid 
elastomer actuators (FEAs), which are driven pneumatically or hydraulically, have 
demonstrated huge promise for these specific applications. However, the requirement 
of a miniature actuation system is still insufficient. The large and cumbersome power 
source trouble the development and  the lack of a lightweight and high-output 
miniature pump has limited the usefulness of soft robotics driven by FEAs. Besides 
the actuation functions, the processing of micro FEAs is still in its infancy. With the 
limitation of technical resolutions, the size of the “micro” FEAs is still in the size of 
millimeters. This research focused on providing solutions to both the two problems to 
push this area forward. 
The first work in this dissertation is to provide a miniature untethered actuation 
solution for soft robotics. Based on the literature review, it still lacks a miniature pump 
with a large flow rate and pressure output although the size and the rigidity have been 
priorly focused on. So comparing the existed solutions, I designed and fabricated a 
miniature pump based on the piezoelectric effect to solve this problem. After that, the 
flow rate and pressure output were measured to optimize the design. The power output 
and the pumping behavior were then also analyzed to detailly describe the pump. And 
finally, I used the pump to drive a pneunet design FEA to prove the availability. In this 
study, I present a compact-size (2 cm3
), lightweight (4.2 g), and high-output 
piezoelectric pump with Bluetooth connectivity. The pump can generate a maximum 
flow rate of 28.8 mL/min or maximum pressure of 100 kPa with a low power 
consumption of 63.5 mW. The design parameters are optimized to achieve the 
maximum flow rate and pressure outputs. The stability and repeatability of our pump 
enable open-loop  control for the actuation of FEAs. A wireless gripper and an 
inchworm-like soft crawler are fabricated by integrating miniature pumps with pneunet bending actuators. These applications demonstrate the versatility of the 
pumps in the untethered actuation of FEAs for autonomous soft robotics. 
Another work of this research provides a massive product fabrication process of 
the micro FEAs. Although the traditional molding and demolding technique shows 
great advantages to fabricate FEAs in the scale of centimeters. The resolution and 
bonding rupture make it challenging to fabricate micro FEAs with same technique. 
Also soft lithography and additive manufacturing process have performed as possible 
solutions, the dimension of the actuators is still normally on the scale of millimeters. 
So in this study, I used direct photolithography process to fabricate the FEAs with a 
critical dimension of tens of micrometers which is in the range of the smallest FEAs. 
This process based on a photolithographic sacrificial layer allows a micro FEA in a 
dimension of 150×150×2100 μm3
 with a critical chamber width of 50 μm. The bending 
behavior is measured in response to the applied pressure. The actuators were also 
evaluated with different membrane thickness, materials, and chamber geometries to 
optimize the performance. And the potential applications are also demonstrated with 
some integrated grippers which were fabricated directly without any other bonding 
process. 

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