Sensor Technologies for Measuring Tongue Biomechanics Relevant to Swallowing: A Narrative Review.

Tongue biomechanics are central to swallowing, yet commonly used clinical assessments provide limited insight into the forces and coordination underlying bolus propulsion. Sensor technologies have emerged to address this gap, but the literature remains fragmented across device classes, calibration approaches, and outcome definitions. This narrative review synthesizes sensor modalities used to characterize tongue biomechanics in dysphagia assessment and rehabilitation. A structured search of biomedical databases identified studies describing pneumatic, piezoelectric, strain gauge, capacitive, optical, and position-tracking systems. Across modalities, consistent physiological patterns are observed, including anterior-to-posterior pressure sequencing and task-dependent modulation with bolus properties. However, cross-study comparison is constrained by variability in sensor configuration, placement, and calibration, limiting the development of shared normative thresholds. To address this, we introduce a comparative maturity framework that situates modalities along a continuum from clinically established to proof-of-concept systems. Pneumatic and piezoelectric devices demonstrate the strongest evidence base and clinical integration, whereas capacitive and optical systems remain early-stage with minimal validation in patient populations. Position-tracking approaches provide complementary kinematic information but remain constrained by cost and ecological validity. Progress will require standardized calibration frameworks, harmonized protocols, and multimodal integration to support clinically interpretable metrics of tongue function.