UC San Diego

The disparity in healthcare access is a large issue in medical deserts, where essential medical resources are distant from the communities they serve. This dissertation advances human-machine interfaces (HMIs) in biomedical applications to facilitate remote medical diagnosis and treatment. The first study is a bi-directional spirometer with flexible capacitive sensors for cost-effective, remote respiratory monitoring. This point-of-care device made of a 3D-printed tube interfacing with the user's mouth and its airflow, successfully measured tidal and deep breathing signals, and highly accurate peak expiratory flow rates compared with commercial device readings.

To enhance the efficacy of virtual healthcare, this work also refines haptic feedback in telemedicine platforms to achieve realistic touch sensations that improve the immersion and accuracy of remote healthcare technologies. It includes a study on wetness perception using a tunable organic hydrogel, achieving a 90% prediction model for human wetness judgment. The results identified that the most effective metrics for high prediction accuracy were those that were the most human-adjacent and enabled the creation of a perceptual space capable of seven distinct levels of wetness. The study demonstrates that the physical characteristics at the skin-stimulus interface are sufficient for simulating wetness without reliance on specific material types.

Additionally, the dissertation investigates contact-free haptic stimulation using thermoelastic and photoacoustic effects. By applying a thin dye layer to the skin, the study demonstrated significant enhancements in the perception of different pulsed light sources, varying in wavelength and pulse width. Notably, it achieved robust tactile stimulation using incoherent light from a commercial Digital Light Processing (DLP) projector. Across all sources, vibration was the predominant felt sensation at the two tested locations: the distal phalanx (i.e., fingertip, 55.21-57.29%) and the proximal phalanx (41.67-44.79%). This contact-free haptic stimulation modality enables convenient, effective transmission of haptic information to human users, potentially at great distances. Collectively, the innovations in this dissertation contribute to the development of virtual technology platforms that enable and enhance remote healthcare delivery.