A curvature-independent high-resolution pressure sensor provides sub-bandage pressure measurement in accordance with Laplace's law

Compression therapy delivered by expert application of bandages or compression garments is a mainstay treatment for several conditions including lymphoedema and chronic wounds. However, it is one of very few clinical interventions where the therapeutic 'dose' is unknown, since sub-bandage pressure is difficult to measure and rarely performed. Laplace's law, describing the pressure differential across a thin, curved membrane provides a theoretical basis for pressure calculation and is used by manufacturers and standards bureaux to quantify compression dose. However, continued discrepancy between measured and theoretical pressures has caused doubt over the applicability of Laplace's law in compression therapy. We propose that this disagreement is caused by alteration of the performance of currently available pressure sensors when deformed on a curved surface, changes in local curvature caused by the sensor itself and by differences in the way sensors are pressurised during calibration versus during use. We have applied Laplace's law to verify the performance of a thin and flexible fibre-optic pressure sensing array, using three different outer packaging designs that vary the sensor's interaction with the bandage and the supporting surface. We verify the applicability of Laplace's law and demonstrate the critical role of local radius in compression measurement.