Four humidity sensors between the absorbent layers of a diaper create a smart diaper capable of detecting wetness and alerting for a change. (Credit: Huanyu “Larry” Cheng/Penn State/Penn State Creative Commons)

A new sensor could help workers in daycares, hospitals, and other settings provide more immediate care to their charges. The new sensor — so cheap and simple to produce that it can be hand drawn with a pencil onto paper treated with sodium chloride — could clear the way for wearable, self-powered health monitors for use not only in “smart diapers” but also to predict major health concerns like cardiac arrest and pneumonia.

As water molecules are absorbed by the paper, the solution becomes ionized and electrons begin to flow to the graphite in the pencil, setting off the sensor, which detects those changes in humidity in the environment and sends a signal to a smartphone, which displays and records the data.

Drawing on the pretreated paper within pretreated lines creates a miniaturized paper circuit board. The paper can be connected to a computer with copper wires and conductive silver paste to act as an environmental humidity detector. For wireless application, such as “smart diapers” and mask-based respiration monitoring, the drawing is connected to a tiny lithium battery that powers data transmission to a smartphone via Bluetooth.

For more information, visit here .