Mechanical engineers at Rice University have designed a chip that allows an ordinary cell phone to detect COVID-19 biomarkers in blood. The new chip could provide a simpler testing process than current nose-swab PCR tests, delivering results in less than one hour without using a laboratory.

Building on technology recently developed for simple biosensing tools that can diagnose malaria and other conditions, the engineering team created a stamp-sized microfluidic chip. The fluid contains micro-particles known as nanobeads that bond with the SARS-CoV-2 N protein, a biomarker for COVID-19. Blood drawn from a finger prick is delivered via a capillary tube to the chip, which fits onto a magnet. 

The magnetic field draws the nanobeads toward a tiny electrochemical sensor coated in “capture antibodies.” When the nanobeads bind to these antibodies, the sensor measures the electric current output. The proportion of current indicates the amount of the biomarker protein in the sample. The chip reads the current signal and sends the results to an app on the smartphone.

The research team used a Google Pixel 2 phone and donated samples from healthy and COVID-19 positive individuals to test the device. The team found that the microchip could accurately detect the protein in concentrations as low as 230 billionths of a gram (230 picograms) per milliliter. 

Longer incubation times yielded accurate results in whole serum (optimally 55 minutes for concentrations as low as 50 picograms). However, diluting the serum resulted in accurate results from lower concentrations in shorter incubation times. When diluted fivefold, accurate results were obtained for a concentration of only 10 picograms in just 25 minutes.

The chip could make rapid COVID-19 results available at the testing site at virtually any location. The engineers published their research in the American Chemical Society journal ACS Sensors.