Ultrasoft Gel Research Articles

Biomimetic Culture of Primary Neurons on an Ultrasoft Gel Surface

Biomimetic Culture of Primary Neurons on an Ultrasoft Gel Surface

Textile EEG Cap using Dry-Comb Electrodes for Emotion Detection of Elderly People

Emotions are fundamental to human life and can impact elderly healthcare encounters between caregiver and patient. Detecting emotions by monitoring the physical signals with wearable smart devices offers new promises for care support. While there are multiple studies on wearable devices, few of these pertain to soft electroencephalogram (EEG) caps designed for long-time wear by elderly people. In this study, a 4-channel textile cap was designed with dry electrodes held by an ultra-soft gel holder, while fashion and ergonomic design features were introduced to enhance wearability and comfort. The dry-electrode textile cap performed highly for monitoring EEG signals; closely matching the wet electrodes equipment. All participants reported positive feedback stating that the textile cap was softer, lighter, and more comfortable than other devices. A cumulative contribution rate of 72.199% for two factors (materials properties factor and design pattern factor) was achieved using the principal factor method (PFA), which are influencing the usability of the wearable devices. An average emotion classification accuracy of 81.32% was obtained from 5 healthy elderly subjects. It was thus concluded that the proposed method provides a stable monitoring and comfortable user experience for users, and can be used to detect emotions for elderly people with good results in the future.

9‐2: Invited Paper: Stretchable Electronics for Wearable Microvolt Biosignal Monitoring Systems

We report on recent progress in large, ultraflexible, and stretchable electronic sensors. Our work focuses on integration technologies for thin‐film electronics comprising ultrasoft gel electrodes, thin‐film amplifiers, Si‐LSI platforms, thin‐film batteries, and information engineering; integrating these technologies enables them to function as imperceptible active sensors.Here, we demonstrate the application of imperceptible sensors for a biosignal monitoring sheet system whose measurement accuracy is 0.1 µV. The most important technology for monitoring very small signals is flexible organic amplification circuits. Taking full advantage of flexible and stretchable electronic technology, we demonstrate wireless sheet electroencephalogram (EEG) monitoring systems for next‐generation telemedicine. The ultraflexible and compliant thin‐film amplifier can amplify biological signals by a factor of 3000, for monitoring of microvolt EEG signals.

Impact of Beads and Drops on a Repellent Solid Surface: A Unified Description.

We investigate freely expanding sheets formed by ultrasoft gel beads, and liquid and viscoelastic drops, produced by the impact of the bead or drop on a silicon wafer covered with a thin layer of liquid nitrogen that suppresses viscous dissipation thanks to an inverse Leidenfrost effect. Our experiments show a unified behavior for the impact dynamics that holds for solids, liquids, and viscoelastic fluids and that we rationalize by properly taking into account elastocapillary effects. In this framework, the classical impact dynamics of solids and liquids, as far as viscous dissipation is negligible, appears as the asymptotic limits of a universal theoretical description. A novel material-dependent characteristic velocity that includes both capillary and bulk elasticity emerges from this unified description of the physics of impact.

Capillary fracture of ultrasoft gels: variability and delayed nucleation.

A droplet of surfactant spreading on an ultrasoft (E ≲ 100 Pa) gel substrate will produce capillary fractures at the gel surface; these fractures originate at the contact-line and propagate outwards in a starburst pattern. There is an inherent variability in both the number of fractures formed and the time delay before fractures form. In the regime where single fractures form, we observe a Weibull-like distribution of delay times, consistent with a thermally-activated process. The shape parameter is close to 1 for softer gels (a Poisson process), and larger for stiffer gels (indicative of aging). For single fractures, the characteristic delay time is primarily set by the elastocapillary length of the system, calculated from the differential in surface tension between the droplet and the substrate, rather than the elastic modulus as for stiffer systems. For multiple fractures, all fractures appear simultaneously and long delay times are suppressed. The experimental protocol provides a new technique for probing the energy landscape and fracture toughness of ultrasoft materials through measurement of the delay time distribution.