Viscoelastic Phase Transition of Polyborodimethylsiloxane (PBDMS) for Mechanical Pass Filters and Noise Fading Sensor

Continuous monitoring of physiological signals is inevitably disrupted by motion artifacts and ambient mechanical noise. Signal processing is typically required to extract genuine physiological signals from motion artifacts, yet the signals can be distorted and classified incompletely. Previously, we presented a noise-selective damper based on gelatin hydrogel and chitosan, however, the hydrogel is unstable due to dehydration. In addition, various types of mechanical filters, such as high-pass, low-pass, and band-pass filters, are needed as alternatives to signal processing. Here, we present viscoelastic polyborodimethylsiloxane (PBDMS) based mechanical pass filters, which maintain stable damping properties for over three months. Dynamic bonding from hydrogen bonds and B─O bonds enables energy dissipation through chain rearrangement and entanglement. The damping behaviors can be tuned by adjusting its molecular weight. As molecular weight increases, the reconfiguration and re-bonding of these chains slow down, resulting in a longer relaxation time. This molecular-weight-dependent relaxation behavior allows precise control over the transition frequency. Furthermore, by parallelly assembling materials with distinct phase transition characteristics, not only high-pass, but also low-pass and band-pass mechanical filtering is achieved. Using PBDMS-based wearable bioelectronics, we successfully separate more than two concurrent mechanical signals without any additional signal processing.