A Smartphone Sensor Can Measure the Heat of Chilis Before You Accidentally Nuke Your Mouth

A chili pepper-shaped device containing a paper-based electrochemical sensor can be connected to a smartphone to reveal how much capsaicin is in a hot pepper.
A chili pepper-shaped device containing a paper-based electrochemical sensor can be connected to a smartphone to reveal how much capsaicin is in a hot pepper.
Image: Adapted from ACS Applied Nano Materials 2020

Popping a random chili into your mouth is the culinary equivalent of playing Russian roulette. Some are mild and packed with flavor, while others will make you feel like you’ve just bitten into the surface of the sun. Without knowing where a chili is from it’s hard to know how hot it is, so researchers from Thailand created a smartphone accessory that can measure the heat.


While most hardware built by researchers looks like it was assembled from random salvaged components found in a hacker’s junk-filled garage, the Chilica-Pod, created at Thailand’s Prince of Songkla University, actually looks like something you could find on the shelf of a Williams-Sonoma store. Shaped like an actual chili, the sensor connects directly to a smartphone and interfaces with an app to provide a measurement of the amount of capsaicin inside a chili, which is the specific ingredient that brings the heat. The higher the concentration of capsaicin there is, the hotter a chili will be, but measuring that usually requires bulky lab equipment. The easier solution, if you’re not comfortable with the heat, is to usually just skip chilis altogether as an ingredient option.

But with the Chilica-Pod users should be able to quickly assess what the experience of eating a given chili will be like before they subject their mouths to all the pain and agony. The sensor uses single-use, paper-based test strips that contain graphene nanoplatelets (thin sheets of graphene in short stacks) enhanced with nitrogen atoms to improve their electrical conductivity. A small sample of a chili, which can be fresh or dried, is mixed into a solution containing ethanol which is then added to the paper strip in small drops. The capsaicin in the drop oxidizes when introduced to the nitrogen-enhanced graphene which produces an electrical current that can be measured. The more current the sensor detects, the higher the concentration of capsaicin in the chili being tested.

The Chilica-Pod has been tested on six different dried chili samples by the team that created it, and so far it has shown a level of accuracy on par with the lab-based hardware and methodologies currently used to measure capsaicin levels in food. The system isn’t quite as self-contained or foolproof as something like a breathalyzer is—it still requires the sample to be mixed into a solution and diluted before being applied to the test strips—so don’t expect to quickly use the Chilica-Pod before digging into a dish. But it could one day be useful in the kitchen, for both professional chefs and home cooks who want to make sure they won’t accidentally be subjecting anyone to an unpleasant experience.


Part of the point of eating something “spicy” is not knowing if it’s going to be “too spicy”.

Having said that, the Scoville scale makes the imperial system look like it was designed by a genius. So I welcome any improvement in the way we measure capsaicin content. A proper scale and measurement would make my poor wife very happy since she wouldn’t need to rely on me saying “no pica” only for it to be fire.