Researchers from the Technion-Israel Institute of Technology in Haifa have developed an innovative sensing system capable of identifying and distinguishing different stimuli. The system is based on origami (the art of paper folding) combined with ink developed at the Technion.

The research, published in Nature Communications, was led by professor Hossam Haick of the Technion’s Wolfson Faculty of Chemical Engineering and the Russell Berrie Nanotechnology Institute, and Dr. Min Zhang, who did his post-doctoral fellowship with Haick. Dr. Zhang is currently an associate professor at East China Normal University.

“Today, there is significant demand for multi-purpose sensing systems for specific purposes,” said Haick. “These systems have great potential as applications in medicine, counterterrorism, food safety, environmental monitoring, ‘the Internet of things,’ and more. The problem is that existing technologies, such as gas chromatography, have many disadvantages, including high cost.”

The challenge facing the researchers was to develop a single system sensitive enough to identify and distinguish among different stimuli. They say they developed a solution inspired by nature. “When we think about the human sensory system, we think of a whole that brings all the data to the brain in a format that it understands. That inspired our development, which is meant to concentrate in a different place all the environmental data we want to monitor. It is a multi-purpose sensory system that absorbs the stimuli and distinguishes among them.”

The system developed by Haick and Dr. Zhang, called “origami hierarchical sensor array” (OHSA), is an integrated array of grouped sensors written on the target object in conductive ink that the two scientists developed. It is a single device that demonstrates sensing abilities and detects physical and chemical stimuli—temperature, humidity, light, and volatile organic particles—at high resolution of time and space. Since it also distinguishes between isomers and chiral enantiomers (forms that are mirror images of each other), it paves new avenues for medical diagnosis. It is worth noting that volatile particle monitoring can be useful in a variety of areas including the diagnosis of disease and monitoring of dangerous substances.

There are many advantages to this unique ink—its low price, the ability to produce it in large quantities, and the simplicity of its application on the target surfaces. The researchers conducted experiments that included control groups (other types of ink) and showed that the special ink attaches itself tightly to materials such as aluminum foil, glass, photo paper, Kapton tape (a polyimide film developed by DuPont in the late 1960s that remains stable across a wide range of temperatures and is used in, among other things, flexible printed circuits and thermal blankets used on spacecraft, satellites, and various space instruments), nitrile (the material used to make disposable gloves), and polydimethylsiloxane (PDMS, used to make contact lenses and for medical technologies and cosmetics).

The ink also allows writing on human skin and nails in a kind of conductive tattoo. It is also waterproof, which may allow, for example, constant monitoring of relevant physiological variables. “We can say that our system identifies the ‘fingerprints’ of chemical and physical stimuli and supplies information about them,” said Haick. Its low cost will make possible its application in many places, including poor areas, for medical and other uses.