I think we all know that the surfaces of our smartphones are dirty places. Like our keys, purses and other items that are handled regularly and rarely cleaned, these things gather dirt, oil, bacteria and, according to scientists at University of California, San Diego, traces of our everyday lives.
A team at the university conducted a study where they swabbed the residue on the screens of 39 volunteers' smartphones. They analyzed over 500 samples of grime and were able to detect a lot of information about the phone's owners like places they've been, medicines they take, food they've eaten and what products they use on their skin, even eye drops. Evidence of sunscreen and mosquito repellant showed up months after they'd last been used.
The scientists were able to discover these things through mass spectrometry, which can identify materials on the molecular level. Every thing that touches our smartphone screens, including the various things contained in the oils on our skin, leaves molecular evidence behind. There can be hundreds to thousands of individual molecules.
Using software that they developed to analyze the results of the mass spectrometry scans, the team was able to isolate and identify the molecules present in the samples. The software then built a profile, or "lifestyle sketch," of each person based on those molecules.
The scientists hope that the technique can be used by law enforcement teams for forensics and solving crimes, but they could also be used in health care to test for the metabolization of medications or to detect a person's exposure to toxic hazardous chemicals.
"Mass spectrometry has been used in forensics for decades to look for explosives and illicit substances," said Pieter Dorrestein, PhD, senior author on the study and professor in UC San Diego School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences. "However, those technologies are typically done in a targeted manner, looking for specific modules. We decided to take a global look at the molecules that are present on objects they touch."
The software takes the molecules found in the samples and runs them against a database of molecules in commercial products that range from personal care to foods to medicines and identifies them by making a match. The matches can be specific down to the brand of the substance.
“You can imagine a scenario where a crime scene investigator comes across a personal object — like a phone, pen or key — without fingerprints or DNA, or with prints or DNA not found in the database. They would have nothing to go on to determine who that belongs to,” said Dorrestein. “So we thought — what if we take advantage of left-behind skin chemistry to tell us what kind of lifestyle this person has?”
For law enforcement groups that could be helpful for identifying suspects in a crime or missing persons. Unfortunately this type of information would also be like gold to marketers looking to target their advertisements and products, but Dorrestein says they have no intention of developing the technology for any other groups outside law enforcement. The mass spectrometry database they created is open source and available to anyone, however.