So, Yuqian Zhang, Ali Yetisen and colleagues wanted to create an optical fiber system that concurrently monitors six key brain health biomarkers: temperature, pH, and concentrations of dissolved oxygen, glucose, sodium ions and calcium ions.

The sensing system accurately determined pH, temperature and dissolved oxygen level in these samples and identified changes in the concentrations of the ions and glucose.

The capsule then began its journey through the stomach, small intestine and large intestine to collect information about pH, temperature and pressure.

Here, the capsule registered a very low pH value, because in the stomach acid is released that breaks down the food.

The gut bacteria produce fatty acids, which cause the pH value to fall again in the first part of the colon.