Author Correction: An ultra-low power wake-Up timer compatible with n-FET based flexible technologies
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An ultra-low power wake-Up timer compatible with n-FET based flexible technologies
Flexible integrated circuits (FlexICs) have drawn increasing attention, particularly in remote sensors and wearables operating in a limited power budget. Here, we present an ultra-low power timer designed to wake-up an external circuit periodically, from a deep-sleep state into an active state, thereby largely reducing the system power consumption. We achieved this with a circuit topology that exploits the transistor’s leakage current to generate a low frequency wake-up signal. This topology is compatible with IC technologies where only n-type transistors are available. The design was implemented with the sustainable FlexIC process of PragmatIC, that is based on Indium Gallium Zinc Oxide (IGZO) thin-film transistors. Our timer generates mean wake-up frequency of 0.24 ± 0.15 Hz, with a mean power consumption of 26.7 ± 14.1 nW. In this paper, we provide details of the Wake-Up timer’s design and performance at different supply voltages, under temperature variations and different light conditions.
Flexible micromachined ultrasound transducers (MUTs) for biomedical applications
The use of bulk piezoelectric transducer arrays in medical imaging is a well-established technology that operates based on thickness mode piezoelectric vibration. Meanwhile, advancements in fabrication techniques have led to the emergence of micromachined alternatives, namely, piezoelectric micromachined ultrasound transducer (PMUT) and capacitive micromachined ultrasound transducer (CMUT). These devices operate in flexural mode using piezoelectric thin films and electrostatic forces, respectively. In addition, the development of flexible ultrasound transducers based on these principles has opened up new possibilities for biomedical applications, including biomedical imaging, sensing, and stimulation. This review provides a detailed discussion of the need for flexible micromachined ultrasound transducers (MUTs) and potential applications, their specifications, materials, fabrication, and electronics integration. Specifically, the review covers fabrication approaches and compares the performance specifications of flexible PMUTs and CMUTs, including resonance frequency, sensitivity, flexibility, and other relevant factors. Finally, the review concludes with an outlook on the challenges and opportunities associated with the realization of efficient MUTs with high performance and flexibility.
Fabrication and modulation of flexible electromagnetic metamaterials
Flexible electromagnetic metamaterials are a potential candidate for the ideal material for electromagnetic control due to their unique physical properties and structure. Flexible electromagnetic metamaterials can be designed to exhibit specific responses to electromagnetic waves within a particular frequency range. Research shows that flexible electromagnetic metamaterials exhibit significant electromagnetic control characteristics in microwave, terahertz, infrared and other frequency bands. It has a wide range of applications in the fields of electromagnetic wave absorption and stealth, antennas and microwave devices, communication information and other fields. In this review, the currently popular fabrication methods of flexible electromagnetic metamaterials are first summarized, highlighting the electromagnetic modulation capability in different frequency bands. Then, the applications of flexible electromagnetic metamaterials in four aspects, namely electromagnetic stealth, temperature modulation, electromagnetic shielding, and wearable sensors, are elaborated and summarized in detail. In addition, this review also discusses the shortcomings and limitations of flexible electromagnetic metamaterials for electromagnetic control. Finally, the conclusion and perspective of the electromagnetic properties of flexible electromagnetic metamaterials are presented.
Revolutionizing wearable technology: advanced fabrication techniques for body-conformable electronics
With the increasing demand for wearable electronic products, there is a pressing need to develop electronic devices that seamlessly conform to the contours of the human body while delivering excellent performance and reliability. Traditional rigid electronic fabrication technologies fall short of meeting these requirements, necessitating the exploration of advanced flexible fabrication technologies that offer new possibilities for designing and fabricating flexible and stretchable electronic products, particularly in wearable devices. Over time, the continuous development of innovative fabrication techniques has ushered in significant improvements in the design freedom, lightweight, seamless integration, and multifunctionality of wearable electronics. Here, we provide a comprehensive overview of the advancements facilitated by advanced fabrication technology in wearable electronics. It specifically focuses on key fabrication methods, including printed electronics fabrication, soft transfer, 3D structure fabrication, and deformation fabrication. By highlighting these advancements, it sheds light on the challenges and prospects for further development in wearable electronics fabrication technologies. The introduction of advanced fabrication technologies has revolutionized the landscape of wearable/conformable electronics, expanding their application domains, streamlining system complexity associated with customization, manufacturing, and production, and opening up new avenues for innovation and development of body-conformable electronics.
Central amygdala somatostatin neurons modulate stress-induced sleep-onset insomnia
Sleep-onset insomnia, characterized by difficulty falling asleep, is linked to increased health risks. Previous studies have shown that the central amygdala (CeA) plays a crucial role in stress regulation, with the somatostatin neurons in the CeA (CeASST+) involved in adaptive stress responses. However, the role of CeASST+ neurons in stress-induced sleep-onset insomnia remains unclear. In this study, we found that the activity of CeASST+ neurons is closely associated with stressful events using fiber photometry in mice. Acute optogenetic activation of CeASST+ neurons induced a rapid transition from non-rapid eye movement (NREM) sleep to wakefulness. Semi-chronic optogenetic and chemogenetic activation of CeASST+ neurons led to prolonged sleep-onset latency and increased wakefulness. Chemogenetic inhibition of these neurons ameliorated sleep-onset insomnia induced by stressful stimuli, but did not affect sleep-wake behavior under physiological conditions. Collectively, our results suggested that CeASST+ neurons are a key neural substrate for modulating stress-induced sleep-onset insomnia, without influencing physiological sleep. These findings highlight CeASST+ neurons as a promising target for treating stress-related sleep-onset insomnia in clinical practice.
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