Reversible Semicrystalline Polymer as Actuators Driven by Organic Solvent Vapor.

A semicrystalline polymer actuator, which is responsive to solvent vapor with fast and large scale locomotion, is described. The thermoset semicrystalline polymer can be easily synthesized from crystallizable polyester segment poly (ε-caprolactone) and isophorone diisocyanate trimer. Organic solvent vapor is used to induce the reversible swelling-crystallization conversion of the crystallizable polyester segment, resulting in its expansion/shrinkage. The contraction of the polymer actuator (1 mm thick) needs only ≈4 s in room temperature. When exposed to air the polymer actuator can exhibit a fast self-oscillation. Then, a soft crawler based on this polymer is demonstrated. Driven by organic solvent it walks rapidly and steadily. The microscope images show the fast swelling-crystallization conversion that gives rise to reversible shape changes of the polymer.

Wearable skin-like optoelectronic systems with suppression of motion artifacts for cuff-less continuous blood pressure monitor.

According to the statistics of the World Health Organization, an estimated 17.9 million people die from cardiovascular diseases each year, representing 31% of all global deaths. Continuous non-invasive arterial pressure (CNAP) is essential for the management of cardiovascular diseases. However, it is difficult to achieve long-term CNAP monitoring with the daily use of current devices due to irritation of the skin as well as the lack of motion artifacts suppression. Here, we report a high-performance skin-like optoelectronic system integrated with ultra-thin flexible circuits to monitor CNAP. We introduce a theoretical model via the virtual work principle for predicting the precise blood pressure and suppressing motion artifacts, and propose optical difference in the frequency domain for stable optical measurements in terms of skin-like devices. We compare the results with the blood pressure acquired by invasive (intra-arterial) blood pressure monitoring for >1500 min in total on 44 subjects in an intensive care unit. The maximum absolute errors of diastolic and systolic blood pressure were ±7/±10 mm Hg, respectively, in immobilized, and ±10/±14 mm Hg, respectively, in walking scenarios. These strategies provide advanced blood pressure monitoring techniques, which would directly address an unmet clinical need or daily use for a highly vulnerable population.

Flexible Hybrid Electronics for Digital Healthcare.

Recent advances in material innovation and structural design provide routes to flexible hybrid electronics that can combine the high-performance electrical properties of conventional wafer-based electronics with the ability to be stretched, bent, and twisted to arbitrary shapes, revolutionizing the transformation of traditional healthcare to digital healthcare. Here, material innovation and structural design for the preparation of flexible hybrid electronics are reviewed, a brief chronology of these advances is given, and biomedical applications in bioelectrical monitoring and stimulation, optical monitoring and treatment, acoustic imitation and monitoring, bionic touch, and body-fluid testing are described. In conclusion, some remarks on the challenges for future research of flexible hybrid electronics are presented.

Ultralow-Cost, Highly Sensitive, and Flexible Pressure Sensors Based on Carbon Black and Airlaid Paper for Wearable Electronics.

Flexible pressure sensors have attracted considerable attention because of their potential applications in healthcare monitoring and human-machine interactions. However, the complicated fabrication process and the cos of sensing materials limit their widespread applications in practice. Herein, a flexible pressure sensor with outstanding performances is presented through an extremely simple and cost-efficient fabrication process. The sensing materials of the sensor are based on low-cost carbon black (CB)@airlaid paper (AP) composites, which are just prepared by drop-casting CB solutions onto APs. Through simply stacking multiple CB@APs with an irregular surface and a fiber-network structure, the obtained pressure sensor demonstrates an ultrahigh sensitivity of 51.23 kPa-1 and an ultralow detection limit of 1 Pa. Additionally, the sensor exhibits fast response time, wide working range, good stability, as well as excellent flexibility and biocompatibility. All the comprehensive and superior performances endow the sensor with abilities to precisely detect weak air flow, wrist pulse, phonation, and wrist bending in real time. In addition, an array electronic skin integrated with multiple CB@AP sensors has been designed to identify spatial pressure distribution and pressure magnitude. Through a biomimetic structure inspired by blooming flowers, a sensor with the open-petal structure has been designed to recognize the wind direction. Therefore, our study, which demonstrates a flexible pressure sensor with low cost, simple preparation, and superior performances, will open up for the exploration of cost-efficient pressure sensors in wearable devices.