The sugar structure is useful here because of the negative space around the grains, which is filled by the polymer – and then because of the negative space left when the sugar dissolves.
“When the sugar grains are removed, that’s where the pores are located,” Dr. Wang explained.
The sponge surface was then converted from hydrophobic to hydrophilic, thanks to an oxygen plasma treatment. Next, the sponge was blanketed in a layer of conductive polymer – a liquid that Dr. Wang likens to black ink – transforming it into an electrode. (Without the oxygen plasma step, the sponge wouldn’t have absorbed the conductive material.) After another oven-curing session, the device was affixed with wires and ready to be used.
The researchers are continuing to refine the concept and hope to develop a wireless wearable device with many spongy electrodes that record signals simultaneously – and that patients can use at home.
In addition to monitoring maternal and fetal health during labor, the researchers say the belt-like device could be used for other types of imaging and diagnosis.
“Depending on the scenario, different signals can be recorded,” Dr. Wang said. “It could be an EMG for a pregnant woman, or an ECG for an athlete or a patient with chronic cardiovascular disease that needs monitoring.”
This work was funded by the Bill & Melinda Gates Foundation (INV-005417, INV-035476). The authors acknowledge the Washington University in St. Louis Institute of Materials Science and Engineering for the use of instruments and staff assistance.
A version of this article first appeared on Medscape.com.