Acid-sensitive pH sensor using electrolysis and a microfluidic channel for read-out amplification

We demonstrated an acid-sensitive pH sensor based on a novel and simple sensing mechanism. Electrolysis bubbles and a microfluidic channel are used for read-out amplification. The amount of hydrogen bubbles generated through electrolysis varies with the pH levels of a buffer solution. The change in volume with respect to pH levels is measured electrically through sensing electrodes. To maximize the change of the pushed liquid column length for a given bubble volume, a microfluidic channel with small cross-sectional area was fabricated and integrated onto the sensing components. For a stronger acid, the change in current increased with increasing liquid column length and higher liquid conductivity. The interplay of these two effects enhanced sensor output, increasing sensitivity at lower pH levels in our sensor.