A Soft-Pneumatic Actuator Array for Tactile Stimulation in Preterm Infants

Preterm infants in neonatal intensive care units (NICUs) experience impaired neurodevelopment and dysregulated stress responses, partly due to a lack of tactile stimulation. Although massage therapy offers proven therapeutic benefits by stimulating C-tactile afferents through (gentle) dynamic touch, existing methods are limited by clinical staff variability and resource constraints. This work presents a compact soft-pneumatic actuator array (SPAA) utilizing four nylon–TPU actuators (modules) connected in series or in parallel to perform a sequential actuation; this array is designed to deliver safe, shear-free, and massage-like normal compression tailored for preterm infants. Actuator performance was characterized using a load-cell and a pressure sensor under different preloads (10–30 g), establishing operating internal pressures of 20–50 kPa, which produced target force ranges between 0.1 and 0.3 N. Two SPAA architectures were evaluated: (i) parallel manifold with branch resistances and (ii) series chain with graded outlet resistances, using passive fluidic sequencing for controlled activation. The series configuration achieved repeatable sequential actuation with programmable delays, essential for mimicking therapeutic massage patterns. These results demonstrate that passive soft-pneumatic sequencing can reliably deliver dynamic tactile stimuli within neurophysiological and safety constraints, laying the groundwork for standardized, automated neonatal massage therapy in NICUs.