Scientists have developed an adhesive patch, which can non-invasively monitor glucose levels in diabetics through the skin, potentially spelling an end for frequent painful finger-prick blood tests. The patch does not pierce the skin, instead it draws glucose out from fluid between cells across hair follicles, which are individually accessed via an array of miniature sensors using a small electric current. The glucose collects in tiny reservoirs and is measured, according to a study published in the journal Nature Nanotechnology. Readings can be taken every 10 to 15 minutes over several hours. Due to the design of the array of sensors and reservoirs, the patch does not require calibration with a blood sample - meaning that finger prick blood tests are unnecessary. Researchers from the University of Bath in the UK hope that it can eventually become a low-cost, wearable sensor that sends regular, clinically relevant glucose measurements to the wearer's phone or smartwatch wirelessly, alerting them when they may need to take action. The advantage of this device is that each miniature sensor of the array can operate on a small area over an individual hair follicle - this significantly reduces inter- and intra-skin variability in glucose extraction and increases the accuracy of the measurements taken such that calibration via a blood sample is not required. "A non-invasive - that is, needle-less - method to monitor blood sugar has proven a difficult goal to attain," said Richard Guy, from the University of Bath. "The closest that has been achieved has required either at least a single-point calibration with a classic 'finger-stick', or the implantation of a pre-calibrated sensor via a single needle insertion," said Guy. "The monitor developed at Bath promises a truly calibration-free approach, an essential contribution in the fight to combat the ever-increasing global incidence of diabetes," he said. "We utilised graphene as one of the components as it brings important advantages: specifically, it is strong, conductive, flexible, and potentially low-cost and environmentally friendly," said Adelina Ilie, from University of Bath. "In addition, our design can be implemented using high-throughput fabrication techniques like screen printing, which we hope will ultimately support a disposable, widely affordable device," she said. In this study the team tested the patch on both pig skin, where they showed it could accurately track glucose levels across the range seen in diabetic human patients, and on healthy human volunteers, where again the patch was able to track blood sugar variations throughout the day. The next steps include further refinement of the design of the patch to optimise the number of sensors in the array, to demonstrate full functionality over a 24-hour wear period, and to undertake a number of key clinical trials.