Scientists have created a non-invasive patch to measure glucose levels through the skin - potentially removing the need for millions of diabetics to carry out finger-prick blood tests.
The patch draws out glucose from fluid between cells across hair follicles, which are individually accessed through a set of miniature sensors using a small electric current. It does not pierce the skin.
Glucose collects in tiny reservoirs and is measured, with readings taken every 10 to 15 minutes over several hours.
Researchers say the array of sensors and reservoirs on the patch mean it does not require calibration with a blood sample, making finger-prick blood tests unnecessary.
The team, from the University of Bath, hope the patch will become a low-cost, wearable sensor that sends regular, clinically relevant glucose measurements to a phone or smartwatch wirelessly - alerting patients when they may need to take action.
Their work is published in the journal Nature Nanotechnology.
Professor Richard Guy, from the university's Department of Pharmacy & Pharmacology, said: "A non-invasive - that is, needle-less - method to monitor blood sugar has proven a difficult goal to attain.
"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.
"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."
An important advantage of the patch is that each miniature sensor 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, the scientists say.
Dr Adelina Ilie, from the Department of Physics, said: "The specific architecture of our array permits calibration-free operation, and it has the further benefit of allowing realisation with a variety of materials in combination.
"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.
"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."
The team tested the patch on pig skin, where they showed it could accurately track glucose levels across the range seen in diabetic human patients, and on healthy human volunteers.
Their next steps include refining the design of the patch to optimise the number of sensors, to demonstrate full functionality over a 24-hour period and to undertake a number of clinical trials.
In the UK, just under 6% of adults have diabetes though up to 50% of adults with the disorder are undiagnosed.
The research was funded by the Engineering and Physical Sciences Research Council (EPSRC), the Medical Research Council (MRC), and the Sir Halley Stewart Trust.