One of the challenging problems in wearable and transdermal biosensing development is mimicking the ex-vivo/on-skin/transdermal situation in the lab setting.
In the adjacent image is one of ZP's closest attempts so far, where we have synthesised an artificial skin, but past which we are very slowly flowing a glucose solution. The glucose solution is exchanging with the solutions in the artificial skin.
The test was done over 7 days. If we focus on the green trace (channel 1 with sensor 1) then we see that we have a stable baseline at 0 mM for day 1 and when the flowing solution is changed from 0 mM to 3 mM at the start of day 1 the signal shows a slow increase. The second sensor in the experiment, the orange trace, (channel 2 with sensor 2) is showing a different response as that sensor is at the edge of artificial skin, and is closer to the glucose source.
The timelines associated with the signal changing in response to the glucose changes is governed by the volume of artificial skin relative to the pump rate, i.e. the faster the pump rate relative to artificial skin volume then faster the transients.