Demands for precise health information tracking techniques are increasing, especially for daily dietry requirements to prevent obesity, diabetes, etc. Many commercially available sensors that detect dynamic motions of the body lack accuracy, while novel strain sensors at the research level mostly lack the capability to analyze measurements in real life conditions. Here, a stretchable, patch‐type calorie expenditure measurement system is demonstrated that integrates an ultrasensitive crack‐based strain sensor and Bluetooth‐enabled wireless communication circuit to offer both accurate measurements and practical diagnosis of motion. The crack‐based strain gauge transformed into a pop‐up‐shaped structure provides reliable measurements and broad range of strain (≈100%). Combined with the stretchable analysis circuit, the skin attachable tool translates variation of the knee flexion angle into calorie expenditure amount, using relative resistance change (R/R0) data from the flexible sensor. As signals from the knee joint angular movement translates velocity and walking/running behavior, the total amount of calorie expenditure is accurately analyzed. Finally, theoretical, experimental, and simulation analysis of signal stability, dynamic noises, and calorie expenditure calculation obtained from the device during exercise are demonstrated. For further applications, the devices are expected to be used in broader range of dynamic motion of the body for diagnosis of abnormalities and for rehabilitation.
We present electrophysiological (EP) signals correlated with cellular cell activities in the adrenal cortex and medulla using an adrenal gland implantable flexible EP probe. With such a probe, we could observe the EP signals from the adrenal cortex and medulla in response to various stress stimuli, such as enhanced hormone activity with adrenocorticotropic hormone, a biomarker for chronic stress response, and an actual stress environment, like a forced swimming test. This technique could be useful to continuously monitor the elevation of cortisol level, a useful indicator of chronic stress that potentially causes various diseases.
As electronics dramatically advance, their components should be fabricated for miniaturized scale, and integrated on limited‐size substrates with extremely high density. Current technologies for the integration and interconnection of electronics show some critical limitations in the application of microscale electronics. To address these problems, herein, a new direct and vertical interconnection driven by selective dewetting of a polymer adhesive is introduced. The interconnection system consists of the polymer adhesive and nanosized metal particles, or structured electrodes. Nanoscale‐dewetting windows formed by controlling the stability and wetting property of the adhesive polymer are controlled by the interfacial property of the coated polymer adhesive. The adhesive is coated on substrate by a simple spin‐coating process, and its ultraviolet curable property allows only the device‐mounted parts to be selectively conductive and sticky, while the other parts form insulation and protection layers. The interconnection of the electronics and substrate by adhesive makes it possible to apply the technique to various microsize electronics with electrode size and pitch of 20 µm or less, and endure dramatic temperature change and a long‐term high humidity environment. Moreover, over display comprising over 10 000 microscale light‐emitting diodes (micro‐LEDs), and commercialized microchips are demonstrated with monolithic integration on flexible and transparent substrate.
In article number 1908422, Tae‐il Kim and co‐workers introduce a facile electrical interconnection method driven by selective dewetting of polymer adhesive, which is applicable to a deterministic microelectronics assembly for flexible electronics. Controlled dewetting of the coated polymeric adhesive is triggered on specific electrode regions, forming vertical interconnection of the microelectronics. Especially, thousands of 30 μm × 60 μm‐scale micro LEDs are demonstrated.
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