Real-time single- and multiple-axis vibrotactile feedback of trunk motion has been shown to significantly decrease mean trunk tilt and decrease time spent outside a no vibrotactile feedback zone (dead zone) in older adults within a laboratory setting. This study aimed to determine if these improvements can translate into everyday use, during which other tasks may simultaneously demand attention. A dual-task paradigm was used in which 10 community-dwelling older adults were asked to perform standing trials in the presence of a secondary task (verbal or push-button), vibrotactile feedback, or both (dual-task). Results show that subjects significantly increased the percentage of time inside the dead zone when feedback was provided compared to when it was not during both verbal (+13.6%) and push-button (+10.1%) secondary tasks. Providing feedback also decreased RMS of trunk tilt during both secondary tasks (verbal: -0.1298; push-button: -0.1388). However, response times for secondary tasks increased (verbal: +119 ms; push-button: +110 ms) when feedback was provided. These results suggest that while vibrotactile feedback does increase attentional load in older adults, it can still be used effectively to improve postural metrics in high cognitive load situations.

Mechanical properties of the extracellular matrix (ECM) have profound effects on cellular functions. Here, we applied novel photosensitive poly-dimethylsiloxane (photoPDMS) chemistry to create photosensitive, biocompatible photoPDMS as a rigidity-tunable material for study of mechanoresponsive cellular behaviors. By modulating the PDMS crosslinker to monomer ratio, UV light exposure time, and post-exposure baking time, we achieved a broad range of bulk Young’s modulus for photoPDMS from 0.027 - 2.48 MPa. Biocompatibility of photoPDMS was assayed and no significant cytotoxic effect was detected as compared to conventional PDMS. We demonstrated that the bulk Young’s modulus of photoPDMS could impact cell morphology, adhesion formation, cytoskeletal structure, and cell proliferation. We further fabricated photoPDMS micropost arrays for multiscale study of mechanoresponsive cellular behaviors. Our results suggested that adherent cells could sense and respond to changes of substrate rigidity at a sub-focal adhesion resolution. Together, we demonstrated the potential of photoPDMS as a photosensitive and rigidity-tunable material for mechanobiology studies.