A simple approach to determining the efficacy of antiperspirants using paper-based colorimetric paper sensors: SweatSENSE

Antiperspirants are commonly used daily, or even multiple times a day, by a large percentage of the global population, in order to address the problems associated with sweating. However, there has been no simple way to test and evaluate the effectiveness of antiperspirants in real time. To address this, we have developed a polydiacetylene based chemosensor that undergoes a blue to red colour change when in contact with acids and alcohols found in sweat, but not when exposed to water. The sensor is prepared via inkjet-printing an imidazolium derivative of a diacetylene monomer onto normal paper to give a transparent square followed by UV curing to produce the navy blue 5 × 5 cm “SweatSENSE” patch. A sensor is applied to the underarm for 5 s and the colour changes to red in the presence of sweat and the intensity of the colour change is recorded. From an in vivo trial involving 52 panellists, the sensor was shown to demonstrate a reduction in total sweat area following the application of an antiperspirant, when compared with a deodorant only control. This sensor will allow consumers to test the effectiveness of their antiperspirants during daily life, in real time, without the need for specialised equipment.