Wireless, Accumulation Mode Dosimeters for Monitoring Pulsed and Non-Pulsed Germicidal Lamps

Abstract

Mitigating the spread of infectious diseases such as the one associated with the COVID-19 pandemic demands simple and effective disinfection techniques. Ultraviolet germicidal irradiation (UVGI) is one such method, in common use for decontamination of hospital rooms. Practical technologies designed to monitor UVGI ensure the delivery of sufficient doses for germicidal efficacy. Existing UVGI dosimeters rely on intermittent measurements of intensity as the basis for a numerical integration scheme that approximates dose. Traditional devices are ineffective, particularly with pulsed UVGI lamps that emit pulses of light with durations shorter than the interval of measurement. Here, we present a compact, accumulation mode dosimeter (AMD) that detects continuously, as opposed to intermittently, at single or multiple UVGI wavelengths. The AMD utilizes an array of photodiodes and supercapacitors to passively transduce and capture photocurrent generated by UVGI without the use of external power. The accumulated voltage across the supercapacitors then serves as a measure of UVGI dose. A key result is that sampling intervals of AMD do not constrain measurement accuracy. When implemented with a wireless transponder, AMD supports a light-adaptive sampling scheme designed to adjust the sampling interval to the intensity and period of UVGI exposure. Compared to time-based sampling schemes adopted by conventional sensors, light-adaptive approaches autonomously optimize battery life by minimizing current consumption during periods of low or no UVGI. Benchtop studies of the use of this technology with pulsed Xenon lamps (pulse ~5 ms) sampled at long intervals (>1s) highlight the key features of operation. Demonstration of AMD during UVGI of E. Coli cultures represents an example in dose dependent effects on disinfection.