The goose bump sensor

A team of researchers at KAIST in Daejeon, South Korea, has developed a flexible, wearable 20 x 20 mm polymer sensor that can directly measure the degree and occurrence of goose bumps (technically known as piloerection) on the skin - caused by sudden changes in body temperature or emotional states.

The technology is based on an electronic device known as a coplanar capacitor and detects goose bumps by virtue of a simple, linear relation between the deformation of the sensor and the decrease of the capacitance.

“We found that the height of the goose bump and the piloerection duration can be deduced by analysing obtained capacitance change trace,” explained Young-Ho Cho. While more work still needs to be done to correlate such physical measurements with emotional states, the work suggests that quantitatively monitoring goose bumps in real time as an indicator of human physical or emotional status is possible, which could pave the way for personalised advertising, music streams or other services informed by direct access to the emotions of the end user.

Through use of microfabrication technology, Cho and colleagues built the sensor using a conductive polymer called PEDOT:PSS for the capacitors, which is flexible compared to brittle metallic conductive materials. The capacitors were embedded in a silicon substrate via a multistep spin-coating process, giving them a spiral shape and coplanar structure. This gave them high capacitive density and high deformability while remaining only 1.2 micrometres thick.

Credit: Young-Ho Cho/KAIST

The silicon substrate, known as Ecoflex 0030, was selected due to its biocompatibility and high degree of flexibility relative to human skin. It is also highly thermal and photo-stable, which allows the embedded polymer devices to maintain their performance in diverse conditions.

They attached these sensors to the inside of a 28-year-old subject’s dorsal forearm and had him grab a hold of ice cubes to induce a sudden cold shock. This stimulated piloerection, deforming the sensors and causing their capacitance to notably decrease.

Future work includes scaling down the signal processing module and capacitance measurement system to be co-mounted on skin with the sensor.

The researchers’ findings are described in the journal Applied Physics Letters, from AIP Publishing.