Final Post

Hello all,

This summer has been quite the experience. Overall the goal was to develop the foundation for an exosuit that is composed entirely of in-house fabricated soft pneumatic actuators that also provides oxygen to the wearer through a face mask. The challenge was to test the behavior of these actuators in an open system (considered open since the breathing process occurs near atmospheric pressure). More specifically we wanted to collect data on these FREE's (fiber reinforced elastomeric enclosures) and see whether or not it deviated significantly from that of industrial McKibbin actuators and FREE's enacted upon within a closed system. The idea was to see whether we could control actuation with enough specificity in an open system in order to bear a load.
The beginning of the summer consisted of learning about the fabrication process behind the FREE's, although as the summer went on my I was primarily tasked with developing and running setups that would appropriately capture the nature of the actuation process of the FREE's and McKibbin actuators in closed and open system by targeting various points of interest while actuation occurred (i.e. pressure differentials before and after the actuator, flow rate, static change in length after actuation, actuator thickness, and terminal pressure differentials). There was certainly a creative process behind what variables to target as well as uncovering the physics behind the contrast and similarities behind actuation in open and closed systems. The consensus was that the pressure reading after actuator was the variable that was most associated with contraction ratio (this was in an open system, considering in a closed system pressure differentials right before and right after the actuator were generally the same). In order to solidify the idea that pressure differentials right after the actuator was the controlling factor behind contraction ratio, we varied the length of the FREE's and re-ran the data. Similar behavior despite the change in length showed actuation was still associated with pressure differentials after the actuator as opposed to penultimate pressure differentials.
Lastly, we wanted to test force output of the FREE's and McKibbin actuators in open and closed systems. We did this by developing a setup that would accommodate block force testing of the actuators in the systems of interest. Again, we also varied length of the FREE's to see if length affected what we theorized to be the main factor behind contraction ratio. The data was still being analyzed when I finished, so I am not sure if flow rate significantly affected force output of the actuators. Based off of observation of the raw data, it did not appear to significantly affect force output despite there being a drop with increased flow rate.
Overall, the next steps may be to consider the effective multiplicative nature of including numerous actuators in sequence or in parallel to study the effects of these FREE's in various arrangements to begin to acquire an idea behind the optimal setup in a system closely related to the finished product.
My best advice to incoming REU's is to keep an open but empty mind coming into the program. When I say empty mind, I mean not to fill your head with answers ahead of time. Be open to suggestions and to the fact that everything you think, may be incorrect. I believe overall that is a healthy way to go into any unknown situation.

Thanks for the experience!