The goose bump sensor is based on an electronic device known as a coplanar capacitor

Goose bump sensor could quantify emotion

A goose bump sensor that could someday be used to measure emotional states has been created by South Korean engineers.

The flexible, wearable 2cm x 20cm polymer sensor can accurately measure the occurrence and quantify the degree of goose bumps – technically known as piloerection – which is 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 in its capacitance, the ability of an object to store an electrical charge.

"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, part of the team of researchers at university KAIST in Daejeon, South Korea, who published their findings in the journal Applied Physics Letters this week.

The researchers concede that more work still needs to be done to correlate such physical measurements with specific emotional states, but the work suggests that quantitatively monitoring goose bumps in real-time as an indicator of human physical or emotional status is possible.

Such a capability could pave the way for personalised advertising, music streams or other services by giving advertising, manufacturing and social media companies direct access to the emotions of the end user.

"In the future, human emotions will be regarded like any typical biometric information, including body temperature or blood pressure," Cho said.

Cho and colleagues built the sensor using a flexible conductive polymer called PEDOT:PSS for the capacitors, which were embedded in a silicon substrate via a multi-step spin-coating process, giving them a spiral shape and coplanar structure that resulted in high capacitive density and high deformability while remaining only 1.2 micrometres thick.

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

To test the device the researchers attached the sensor to the upper side a 28-year old subject's forearm and had him grab hold of ice cubes to induce a sudden cold shock, which stimulated piloerection, deforming the sensors and causing their capacitance to notably decrease.

The results using the human subject closely mirrored those achieved by the researchers when using artificial goose bumps made using silicon-based polymer PDMS attached to a syringe and a pressure sensor, supporting the efficacy of the system.

A positive change in capacitance was actually measured between the successive attemtps to artificially stimulate piloerection indicating that the subject’s skin had become more flat than initial condition, which the researchers put down to ambient temperature or possible nervousness of the subject.

The researchers suggest that future work should focus on scaling down the signal processing module and capacitance measurement system so that they can also be mounted on skin with the sensor, rather than externally as is currently the case.

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