Soft, skin-interfaced microfluidic platforms are capable of capturing, storing, and assessing sweat chemistry and total sweat loss, which provides essential insight into human physiological health.
Mechanical
instabilities in soft materials have led to the formation
of unique surface patterns such as wrinkles and cracks for a wide
range of applications that are related to surface morphologies and
their dynamic tuning. Here, we report a simple yet effective strategy
to fabricate strain-tunable crack and wrinkle microvalves with dimensions
responding to the applied tensile strain. The crack microvalves initially
closed before stretching are opened as the tensile strain is applied,
whereas the wrinkle microvalves exhibit the opposite trend. Next,
the performance of crack and wrinkle microvalves is characterized.
The design predictions on the bursting pressure of microvalves and
others from the theory agree reasonably well with the experimental
measurements. The microfluidic devices with strain-tunable crack and
wrinkle microvalves have then been demonstrated for microsphere screening
and programmable microfluidic logic devices. The demonstrated microfluidic
devices complement the prior studies to open up opportunities in microparticle/cell
manipulations, fluidic operations, and biomedicine.
Elastomeric encapsulation layers are widely used in soft, wearable devices to physically isolate rigid electronic components from external environmental stimuli (e.g., stress) and facilitate device sterilization for reusability. In devices experiencing large deformations, the stress-isolation effect of the top encapsulation layer can eliminate the damage to the electronic components caused by external forces. However, for health monitoring and sensing applications, the strain-isolation effect of the bottom encapsulation layer can partially block the physiological signals of interest and degrade the measurement accuracy. Here, an analytic model is developed for the strain- and stress-isolation effects present in wearable devices with elastomeric encapsulation layers. The soft, elastomeric encapsulation layers and main electronic components layer are modeled as transversely isotropic-elastic mediums and the strain- and stress-isolation effects are described using isolation indexes. The analysis and results show that the isolation effects strongly depend on the thickness, density, and elastic modulus of both the elastomeric encapsulation layers and the main electronic component layer. These findings, combined with the flexible mechanics design strategies of wearable devices, provide new design guidelines for future wearable devices to protect them from external forces while capturing the relevant physiological signals underneath the skin.
Electronic Supplementary Material
Supplementary material is available in the online version of this article at 10.1007/s11431-022-2034-y.
<p>Affected by COVID-19, “cloud tourism” has become a new way of forest tourism. Based on the survey data of 778 Internet respondents, frequency analysis and binomial Logistic regression model were used to analyze the preference and influencing factors of respondents’ participation in forest cloud tourism. The results show that the respondents prefer to relax in terms of travel motivation; In terms of tourism content, they prefer forest sightseeing activities. In terms of the mode of tourism video playback, they prefer short video or live broadcast; Preferred social media and short video software in terms of platform selection; In terms of playing time, they prefer the videos of 21–40 minutes; Prefer natural sounds or soft music in the background. Variables such as gender, age, education level, occupation, income level, travel restriction and travel experience are the main factors influencing consumers’ choice of forest cloud tourism activities. Therefore, it is suggested that the content of forest cloud tourism should be relaxing, the video playing time should be 21–40 minutes, and step charging mode should be adopted.</p>
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