• The following procedure was followed to conduct this test
  • System was connected as shown above in Figure 3
  • DAQ was turned on to start collecting data and the peristaltic pump was turned onto its highest setting on the dial which gives a flow rate of roughly 40mL/min
  • The cup was gently placed on the individual’s forearm and data was collected for 5 seconds after which the cup was taken off the forearm. This was repeated two additional times to gather three test results to be able to analyze and compare.
    • From phase 4, 10 seconds was found to be a test length that allows desired deformation to be reached. This was again reflected in these test results.
• Figure 7 above shows the data collected through this procedure where the orange line shows the values of sensor 2 which was connected to the side hole in the cup while the blue line shows the data from sensor 1 connected to the t-splitter and top port of the cup.
• Both sensors drop in PSI reading simultaneously and read the same value as the individual’s skin is deformed. Once the skin deforms 1mm and blocks the small opening in the cup, the pressure in sensor 1 continued to drop as the peristaltic pump was still displacing air out of the tubes while sensor 2 detected no drop in pressure.
• This confirms what the team expected would happen when a 1mm deformation would be achieved and the opening was sealed off leading to the difference in pressure between the two sensors. In addition, the three tests conducted on the same area show similar results showing how the results are repeatable. This data shows that the system can detect a change in pressure and properly graph the results
  • The success of these tests indicates that further system redesign is not needed.

Further Tests

• Further prototyping tests for product functionality involves three main components: identifying suitable materials to use for continued testing, determining the settling time of the pump, and collecting data from the aforementioned materials.
• To determine the functionality of the beta prototype, it is relevant to test the prototype on materials that would provide similar results as skin with known material properties
  • Potential materials for further use in testing: saran wrap, rubber erasers, rubber bands, swim caps, rubber jar openers, and meat (chicken or beef).
• The settling time test will help determine at what point after turning on the device does the flow rate of the pump become steady. Steps are as follows:
  • Turn on the pump at 75% power. Start collecting pressure data immediately.
  • Collect data for 30 seconds. Create pressure vs. time graph.
  • Determine at what time point the output (pressure) does not deviate from the final pressure value by more than 5% of that value.
    • This will be determined to be the settling time of the system, and the time after which the team will be able to collect reliable data.
  • Repeat the test two additional times to ensure consistency in the measurements.
• The final functionality test of the device will involve running the device on the aforementioned testing materials. Steps are as follows:
  • Turn on the pump at 75% power. Allow to run until for aforementioned settling time.
  • Place probe on the skin. Start timer.
  • Collect pressure readings from both sensors for ten seconds.
  • At ten seconds, stop data collection and turn off the pump. Turn the manual valve to vent built up pressure.
  • Remove probe from material.
  • Generate pressure vs time curves. Repeat the test two additional times.
• The results from this test will be used for final analysis of the mechanical properties of the skin discussed in the following section.

Upcoming Modeling and Simulation

• In continuing simulations, the team will use modeling software FEBio to compare finite element model simulations to the data that is collected using the beta prototype
  • FEBio is a finite element analysis software that was designed to be applied in biomechanics/bioengineering applications
• To prove the effectiveness of the beta prototype, data will be collected from household materials with known mechanical properties and parallel suction/pressure simulations will be run in FEBio
  • The results of the data collection and the FEBio simulations will be compared against one another to determine how much error is present in the physical system and how effective it is at collecting accurate pressure data
• Once the beta prototype has been proven effective in this manner, the team will use iterative methods to deduce the mechanical properties of the skin by collecting data and using it to infer the mechanical properties used in the FEBio simulation
  • Once the results of the simulation match the results collected with the beta prototype (within a certain level of error), it can be assumed that the mechanical properties used are the true properties of the skin.