Researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia made use of common household supplies to develop low-cost skin sensors that monitor touch, pressure, temperature, acidity and humidity.

Low-cost skin sensor made from household supplies. Image source: KAUST Paper-based skin with real-time sensing capability was assembled from off-the-shelf materials such as aluminum foil, tape, sticky notes, napkins and sponges. The sensory platform is connected to a device that detects changes in electrical conductivity according to external stimuli.

The sensor design exploits different properties of the materials. For example, the conductivity of sponges and wipes provides a reading on humidity, while a pH pencil line on top of paper records acidity levels. Aluminum foil with conductive silver ink detects temperature differences.

Increasing levels of humidity increase the platform’s ability to store an electrical charge, or its capacitance. Exposing the sensor to an acidic solution increases its resistance, while exposing it to an alkaline solution decreases it. Voltage changes are detected with temperature changes, and bringing a finger closer to the platform disturbs its electromagnetic field, decreasing its capacitance.

Several challenges remain before a fully autonomous, flexible and multifunctional sensory platform becomes commercially achievable. For one thing, wireless interaction with the paper skin needs to be developed. Reliability tests also need to be conducted to assess how long the sensor can last and how accurate its performance is under severe bending conditions.