Reproducible Transpalpebral Intraocular Pressure Sensing Enabled by Low-Energy-Barrier Ion Pumping

Abstract

Elevated intraocular pressure (IOP) is a major risk factor for blindness in glaucoma patients, highlighting the critical need for continuous IOP monitoring. While traditional transpalpebral tonometers (TTs) circumvent corneal contact by adopting Goldmann applanation principles through impulsive corneal flattening forces, their measurement accuracy is inherently compromised by eyelid-induced cushion effects. In contrast, parallel-plate capacitive sensors employ constant compressive loading upon the eyelid, achieving palpebral compaction to mitigate the cushion effects. More recently, ion-pump-based capacitive sensors have emerged as promising alternatives, particularly due to their enhanced sensitivity. Nevertheless, these sensors exhibit sharp sensitivity deterioration at extended measurement ranges (0–10 kPa). This operational constraint originates from the strong hydrogen bond energies (between confining matrices and ions) and rigid block copolymer matrices’ steric hindrance. To address these limitations, we developed a transpalpebral tonometer featuring low-energy-barrier ion pumps, incorporating (3-aminopropyl)triethoxysilane (APTES)-silanized liquid metal nanoparticles (LM NPs) as confining matrices and an ionic liquid as an ion donor. The low-energy barrier arises from (1) weaker hydrogen bonds between the N–H of APTES and the F of the ionic liquid and (2) reduced crystallinity in the elastomeric matrices induced by LM NPs. Our sensor achieves a sensitivity of 24.88 kPa^–1 with maintained linearity over 0–85 kPa. In vivo animal trials over 120 min validated its continuous IOP monitoring capability, reliably detecting elevated IOP states and demonstrating clinical potential for glaucoma management.