ABSTRACT
This paper reports a type of highly sensitive temperature sensor utilizing AlN-on-Si resonators with coupled-beam structures of double- and triple-ended-tuning-fork (D/TETF). For both resonators, the out-of-plane flexural mode is adopted as it favors the effect of thermal mismatch between the composite layers inherent to the AlN-on-Si structure and thus helps attain a large temperature coefficient of resonant frequency (TCF). The analytical model to calculate TCF values of D/TETF AlN-on-Si resonators is provided, which agrees well with the finite-element simulation and experimental results. The resonant temperature sensor is built by closing the loop of the AlN-on-Si resonator, a transimpedance amplifier, a low-pass filter, and a phase shifter to form an oscillator, the output frequency of which shifts proportionally to the ambient temperature. The measured sensitivities of the temperature sensors using D/TETF resonators are better than -1000 ppm/°C in the temperature range of 25°C~60°C, showing great potential to fulfill the on-chip temperature compensation scheme for cofabricated sensors.
ABSTRACT
In recent years, wearable electronic devices have made considerable progress thanks to the rapid development of the Internet of Things. However, even though some of them have preliminarily achieved miniaturization and wearability, the drawbacks of frequent charging and physical rigidity of conventional lithium batteries, which are currently the most commonly used power source of wearable electronic devices, have become technical bottlenecks that need to be broken through urgently. In order to address the above challenges, the technology based on triboelectric effect, i.e., triboelectric nanogenerator (TENG), is proposed to harvest energy from ambient environment and considered as one of the most promising methods to integrate with functional electronic devices to form wearable self-powered microsystems. Benefited from excellent flexibility, high output performance, no materials limitation, and a quantitative relationship between environmental stimulation inputs and corresponding electrical outputs, TENGs present great advantages in wearable energy harvesting, active sensing, and driving actuators. Furthermore, combined with the superiorities of TENGs and fabrics, textile-based TENGs (T-TENGs) possess remarkable breathability and better non-planar surface adaptability, which are more conducive to the integrated wearable electronic devices and attract considerable attention. Herein, for the purpose of advancing the development of wearable electronic devices, this article reviews the recent development in materials for the construction of T-TENGs and methods for the enhancement of electrical output performance. More importantly, this article mainly focuses on the recent representative work, in which T-TENGs-based active sensors, T-TENGs-based self-driven actuators, and T-TENGs-based self-powered microsystems are studied. In addition, this paper summarizes the critical challenges and future opportunities of T-TENG-based wearable integrated microsystems.
ABSTRACT
Acute skin defects often cause many adverse events such as abnormal pigmentation and scar formation, the satisfactory healing of which remains a significant clinical challenge. Over the past several decades, a number of skin equivalents have been available for clinical purposes to promote wound closure. However, the true values of skin equivalent - tissue-engineered skin (TE-skin) composed of neonatal fibroblasts and keratinocytes - in improving the quality of wound healing are not yet elucidated. A total of 158 patients were enrolled, 129 of which were used in this study. In these patients, acute skin defects were treated with TE-skin as experimental group, and treated with Vaseline primary dressing as control group. The differences in average healing times between the two groups were determined with statistical analysis according to different depths of skin defects. Wound quality, including pigmentation, cicatrization, and pliability, was assessed by investigators from different clinical centers over a 6-month period. The cosmetic outcome of the wound was further evaluated with histological method. In the study, the average time of wound closure in the experimental group was significantly shortened by 6.5 to 20 days according to different depths of skin defects. The cosmetic quality of reconstructed skin was satisfactory, with the patients enjoying better pliability, less abnormal pigmentation, and cicatrization. Safety analysis demonstrated that the wounds treated with TE-skin did not show clinical or laboratory evidence of rejection during the trial. These results indicate that TE-skin is a suitable and clinically effective treatment for various acute skin defects. Furthermore, the TE-skin appears to produce more satisfactory cosmetic results when compared with the conventional therapy.
