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3D Printed Electronic Patch for pH and Hydration Sensing
A B

Figure 5. Hysteresis plot (A) and (B) made by using mean data points of Figure S4a and S4b, respectively.

Figure 6. Resistance versus time plots indicating change in hydration.
resistance depends on below equations with change in 4. Conclusions
fluid content and surface area of electrodes in contact
with the fluid. The work demonstrates the feasibility of fully printing
a wound management patch. The wound patch was
fabricated with the purpose of enhancing wound. The
U
R = (1) focus is to measure the health status of the wound through
I indicative pH and hydration levels in a single patch.
A PDMS-based substrate was used to print SWCNT and
silver functional inks as sensing elements. Inkjet printing
L
R = ρ (2) was employed for the patch and optimized to get the
A desired design and dimensions. The fabricated sensor
patch has a sensitivity of 7.1 ohm/pH for wound pH

where R = eesistance (Ω), U = voltage (V), levels. The measured resistance changes suggested that
I = current (A), ⍴= resistivity (Ω m), L = length between the sensor is able to measure wound exudate and serve as
electrodes (m), and A = surface area of electrodes (m ). detector for wound fluids. It was also concluded that the
2
The sensor patch was fabricated for the purpose of sensitivity and precision of the patch can be controlled
validating the measurements for wound management. by removal of excess SWCNTs and through the printing
The hydration sensor gives an indication of the process.
presence of fluid in the wound, and if that is true, the Acknowledgments
measurements of the pH sensor originate from the
wound fluid and not the dried-out residue left on the This work was supported by the Dean Start-up grant,
pH sensor. Science and Technology, Aarhus University, Denmark.

46 International Journal of Bioprinting (2022)–Volume 8, Issue 1