At-home blood pressure monitors enable patients to collect BP data, but only present information representing one moment in time. Continued monitoring requires ongoing readings using a monitor and cuff, but data are lost when the monitor’s not in use, such as when the patient sleeps.

The rise of wearable technologies is helping to bridge this gap, and now, researchers have developed a novel method of continuous BP monitoring: temporary tattoos.

Challenges of older tech

Many of these existing technologies use acoustic, pressure, or optical modalities to measure BP, but they’re fairly large and generally aren’t compatible with the skin’s elasticity.

Acoustic models typically use miniaturized, wearable ultrasound (US) transducers coupled with bulky US generators that cannot be worn. Research published in Nature Nanotechnology indicates that wearable US transducers often slide around during movement, so they need frequent recalibration due to sensor displacement, which is not very feasible on a daily basis.

Kireev D, Sel K, Ibrahim B, et al. Continuous cuffless monitoring of arterial blood pressure via graphene bioimpedance tattoos. Nature Nanotechnology. 2022;17(8):864–870.

These sensors are capable of estimating heart rate using data from the skin’s surface and underlying capillary beds. Unfortunately, the BP pulse wave is not capable of effectively reaching any capillaries, making this modality an unreliable method of estimating BP.

In 2022, scientists at the University of Texas at Austin and Texas A&M University developed a temporary tattoo BP monitoring device that records bioimpedance measurements taken directly from arteries. Each tattoo is self-adhesive and low-impedance, perfect for continuous remote BP monitoring for up to 5 hours at a time.

Within each tattoo, graphene helps conduct small electrical currents directly through the skin and underlying tissue.

Kireev D, Kampfe J, Hall A, et al. Graphene electronic tattoos 2.0 with enhanced performance, breathability and robustness. npj 2D Mater Appl. 2022;6(1):46.

Temporary tattoos featuring graphene were initially introduced in 2017; however, these monolayer graphene systems showed impedance higher than commercial gel electrodes, and any grain boundaries or large cracks or folds may drastically reduce their overall performance.

Unlike previous generations of monitoring tattoos, they allow underlying skin to sweat and breathe normally, while still collecting accurate BP data.

GETs demonstrate accuracy during testing

In this study, researchers placed graphene electronic tattoos (GETs) on seven subjects who then performed various exercises to intentionally raise their BP. Throughout the experiment, there were no complaints of skin damage, irritation, redness, or allergic reactions.

The placement of thirteen GETs on each participant—one set injecting alternating currents at 10kHz directly into tissue while the others recorded subsequent changes in biopotentials—enabled continuous BP monitoring in an innovative manner. Because the electrical currents penetrate deeply into tissues, the tattoos sensed various hemodynamic parameters from the arteries themselves.

These data generated BP measurements with a demonstrated accuracy of 0.2 ± 4.5 mmHg for diastolic BP, 0.2 ± 5.8 mmHg for systolic BP, and 0.1 ± 5.3 mmHg for mean arterial pressure. The GETs are also smaller and don’t slide around on the skin surface, resulting in bioelectrical impedance analysis without the need for frequent recalibration.

However, the researchers anticipate that they will be widely available within the next 5 years.