Disinfection of Smartphones using QED induced UV-C

PITTSBURGH - April 9, 2015 - PRLog -- .

Background
Smart Phones are commonplace all over the world. Operated with touchscreens, Smartphones unfortunately provide a natural way to transmit infectious viruses acquired in touching public surfaces. Phones passed around to share photos including computers in public librarires, viruses are readily accumulate and are transmitted between people through the fingers. In a Chicago office, Smartphones were found [1] to show abnormally high numbers of coliforms, a bacteria indicating fecal contamination. Indeed, about 30% of bacteria present on your smartphone end up on its users hands: pass the phone around to friends to share photos and you have increased the contamination. A British study found Smartphones carried 18 times more bacteria than a flush handle in a toilet and an article in the journal of “Annals of Clinical Microbiology and Antimicrobi­als” found that over 90% of phones used by hospital staff members were contaminated with bacteria.

However, if only you use your Smartphone, you're probably pretty safe from the spread of viruses from others. But as soon as you touch public surfaces such as handrails and grab poles in Public Transportation trains and buses, viruses start accumulating on your phone’s touch screen that can make you ill. Periodic cleaning would remove the pathogens, but can damage your phone. Wiping down your device with a moist microfiber cloth was sufficient to eliminate many kinds of common bacteria. But bacteria like clostridium difficile (which can cause diarrhea or even inflammation of the colon) and flu viruses [2] may require a sterilizing agent like bleach or alcohol, but this is not done for fear of damaging the touch screen.

Until now, disinfecting Smartphones with soap or bleach is claimed superseded by the PhoneSoap Charger [3] using UV-C lamps. The phone is placed in a compartment (153 mm x 95 mm x 20 mm) for about 4 minutes. Heat, liquids, and chemicals that can damage the phone are not used. Of note, UV-C lamps and not LEDs are used in the PhoneSoap Charger.

Problems
Currently, LED’s in the UV-C are limited to EQE of a few percent [4] and not expected to impact the disinfection market until 2017/2018. EQE stands for external quantum efficiency. LEDs are used to produce UV-A and –B, but the disinfection capability is reduced [5] compared to UV-.C. Longer exposure times are required to reach the dosage necessary for disinfection.

Proposal
QED induced EM radiation emitted from the touch screen of Smartphones from body heat or that dissipated by the electronics itself is proposed to provide the UV-C from which infectious viruses may promptly be disinfected. Instead of the 4 minutes required for PhoneSoap Charger disinfection, QED disinfection only takes a few seconds.  QED stands for quantum electrodynamics, EM for electromagnetic, and UV-C for ultraviolet radiation at 254 nm. Phone touch screens would be provided with a permanent 50-60 nm ZnO coating that can be periodically cleaned to minimize pathogen residue. The UV-C from typical Smartphones provided with a nano-coated touch screen is depicted in the thumbnail.

The ZnO nano-coated touchscreen is similar to the recently proposed QED induced disinfection of viruses from handrails and grab poles in Public Transportation train cars and buses in Hong Kong. See
http://www.prlog.org/12441541-qed-disinfection-of-future-...

Theory and Analysis
QED induced Smartphone disinfection produces UV-C as the body heat of the hand holding the underside of the phone including the Joule heat dissipated in the phone electronics is transferred to the nano-coated ZnO touchscreen. Because of QM, the body and electronic heat cannot increase the temperature of the coating as its heat capacity vanishes under TIR confinement. QM stands for quantum mechanics and TIR for total internal reflection. Instead, the heat is conserved by QED inducing its conversion to EM radiation which can be tuned to the UV-C by proper selection of the coating thickness. See numerous QED applications at http://www.nanoqed.org

The TIR confinement only occurs as the body and electronic heat flows into the ZnO nano-coating. The TIR wavelength λ of the EM radiation is, λ = 2 n d, where, n and d are the refractive index and thickness of the coating. The ZnO coating having n = 2.4 only needs to be higher than that of the touchscreen surface, typically glass having n of about 1.5. Hence, QED spontaneously creates EM radiation in the UV-C at λ = 254 nm for a coating having thickness d = 53 nm.

Conclusions
In Smartphones, QED induced UV-C radiation from body and electronics heat offers the advantage of continuous disinfection of diseases from being transmitted by touchscreens.  No additional heat is necessary.

The much publicized superiority of LEDs in the UV-A and B over conventional lamps is not yet proven for UV-C disinfection. Even if UV-C LEDs are developed, QED induced UV-C disinfection is far simpler as a ZnO nano-coating positioned near the pathogen only needs to be driven by body heat and at most small mW electrical heaters.

In Public Transportation train cars and buses, Smartphones are used by almost all passengers all the time. What this means is passengers themselves may use QED induced UV-C from their Smartphones to disinfect viruses they acquire upon touching handrails and grab poles, as they must to avoid falling during sudden train and bus motions.

Periodic UV-C disinfection during the overnight charging of the Smartphone as embodied in the PhoneSoap Charger is not required upon nano-coating touchscreens, although pathogen residue needs to be removed periodically with a moist cloth.

References
[1]  “ UV LED Cell Phone Disinfection,” Sensor Electronic Technology, Inc., 1195 Atlas Road, Columbia, SC 29209
[2]  Cleaning the Mobile Germ Warehouse - NYTimes.com.htm
[3]  “UV Cell Phone Sanitizer & Universal Charger _ PhoneSoap Charger Smartphone Cleaner.htm
[4]  P. Mukish, 2015. UV LED - Technology, Manufacturing and Application Trends in disinfection, Yole Developpement.
[5]  MRSA-UV - Advanced Total Room UV Sanitizing Equipment - MRSA-UV.com.htm