Doping Engineering of Conductive Polymers and Their Application in Physical Sensors for Healthcare Monitoring

Physical sensors have emerged as a promising technology for real-time healthcare monitoring, which tracks various physical signals from the human body. Accurate acquisition of these physical signals from biological tissue requires excellent electrical conductivity and long-term durability of the sensors under complex mechanical deformation. Conductive polymers, combining the advantages of conventional polymers and organic conductors, are considered ideal conductive materials for healthcare physical sensors due to their intrinsic conductive network, tunable mechanical properties, and easy processing. Doping engineering has been proposed as an effective approach to enhance the sensitivity, lower the detection limit, and widen the operational range of sensors based on conductive polymers. This approach enables the introduction of dopants into conductive polymers to adjust and control the microstructure and energy levels of conductive polymers, thereby optimizing their mechanical and conductivity properties. This review article provides a comprehensive overview of doping engineering methods to improve the physical properties of conductive polymers and highlights their applications in the field of healthcare physical sensors, including temperature sensors, strain sensors, stress sensors, and electrophysiological sensing. Additionally, the challenges and opportunities associated with conductive polymer-based physical sensors in healthcare monitoring are discussed.

Plants' Response to Abiotic Stress: Mechanisms and Strategies

Abiotic stress is the adverse effect of any abiotic factor on a plant in a given environment, impacting plants' growth and development. These stress factors, such as drought, salinity, and extreme temperatures, are often interrelated or in conjunction with each other. Plants have evolved mechanisms to sense these environmental challenges and make adjustments to their growth in order to survive and reproduce. In this review, we summarized recent studies on plant stress sensing and its regulatory mechanism, emphasizing signal transduction and regulation at multiple levels. Then we presented several strategies to improve plant growth under stress based on current progress. Finally, we discussed the implications of research on plant response to abiotic stresses for high-yielding crops and agricultural sustainability. Studying stress signaling and regulation is critical to understand abiotic stress responses in plants to generate stress-resistant crops and improve agricultural sustainability.

Heterogeneous Multi-Material Flexible Piezoresistive Sensor with High Sensitivity and Wide Measurement Range

Flexible piezoresistive sensors (FPSs) have the advantages of compact structure, convenient signal acquisition and fast dynamic response; they are widely used in motion detection, wearable electronic devices and electronic skins. FPSs accomplish the measurement of stresses through piezoresistive material (PM). However, FPSs based on a single PM cannot achieve high sensitivity and wide measurement range simultaneously. To solve this problem, a heterogeneous multi-material flexible piezoresistive sensor (HMFPS) with high sensitivity and a wide measurement range is proposed. The HMFPS consists of a graphene foam (GF), a PDMS layer and an interdigital electrode. Among them, the GF serves as a sensing layer, providing high sensitivity, and the PDMS serves as a supporting layer, providing a large measurement range. The influence and principle of the heterogeneous multi-material (HM) on the piezoresistivity were investigated by comparing the three HMFPS with different sizes. The HM proved to be an effective way to produce flexible sensors with high sensitivity and a wide measurement range. The HMFPS-10 has a sensitivity of 0.695 kPa^-1, a measurement range of 0-14,122 kPa, fast response/recovery (83 ms and 166 ms) and excellent stability (2000 cycles). In addition, the potential application of the HMFPS-10 in human motion monitoring was demonstrated.

Mechanoluminescence Rebrightening the Prospects of Stress Sensing: A Review

The emergence of new applications, such as in artificial intelligence, the internet of things, and biotechnology, has driven the evolution of stress sensing technology. For these emerging applications, stretchability, remoteness, stress distribution, a multimodal nature, and biocompatibility are important performance characteristics of stress sensors. Mechanoluminescence (ML)-based stress sensing has attracted widespread attention because of its characteristics of remoteness and having a distributed response to mechanical stimuli as well as its great potential for stretchability, biocompatibility, and self-powering. In the past few decades, great progress has been made in the discovery of ML materials, analysis of mechanisms, design of devices, and exploration of applications. One can find that with this progress, the focus of ML research has shifted from the phenomenon in the earliest stage to materials and recently toward devices. At the present stage, while showing great prospects for advanced stress sensing applications, ML-based sensing still faces major challenges in material optimization, device design, and system integration.

Stress Monitoring and Recent Advancements in Wearable Biosensors

The stress response allows the body to overcome obstacles and prepare for threats, but sustained levels of stress can damage one's health. Stress has long been measured through physical tests and questionnaires that rely primarily on user-inputted data, which can be subjective and inaccurate. To quantify the amount of stress that the body is experiencing biologically, analytical detection of biomarkers associated with the stress response recently have been developed. Novel stress sensing devices focus on cortisol sweat sensing as a part of wearable, flexible devices. These devices promise a real-time, continuous collection of stress data that can be used in clinical diagnoses or for personal stress monitoring and mediation.

Pivotal roles of environmental sensing and signaling mechanisms in plant responses to climate change

Climate change reshapes the physiology and development of organisms through phenotypic plasticity, epigenetic modifications, and genetic adaptation. Under evolutionary pressures of the sessile lifestyle, plants possess efficient systems of phenotypic plasticity and acclimation to environmental conditions. Molecular analysis, especially through omics approaches, of these primary lines of environmental adjustment in the context of climate change has revealed the underlying biochemical and physiological mechanisms, thus characterizing the links between phenotypic plasticity and climate change responses. The efficiency of adaptive plasticity under climate change indeed depends on the realization of such biochemical and physiological mechanisms, but the importance of sensing and signaling mechanisms that can integrate perception of environmental cues and transduction into physiological responses is often overlooked. Recent progress opens the possibility of considering plant phenotypic plasticity and responses to climate change through the perspective of environmental sensing and signaling. This review aims to analyze present knowledge on plant sensing and signaling mechanisms and discuss how their structural and functional characteristics lead to resilience or hypersensitivity under conditions of climate change. Plant cells are endowed with arrays of environmental and stress sensors and with internal signals that act as molecular integrators of the multiple constraints of climate change, thus giving rise to potential mechanisms of climate change sensing. Moreover, mechanisms of stress-related information propagation lead to stress memory and acquired stress tolerance that could withstand different scenarios of modifications of stress frequency and intensity. However, optimal functioning of existing sensors, optimal integration of additive constraints and signals, or memory processes can be hampered by conflicting interferences between novel combinations and novel changes in intensity and duration of climate change-related factors. Analysis of these contrasted situations emphasizes the need for future research on the diversity and robustness of plant signaling mechanisms under climate change conditions.

The role of central nervous system development in late-onset neurodegenerative disorders

The human brain is dependent upon successfully maintaining ionic, energetic and redox homeostasis within exceptionally narrow margins for proper function. The ability of neurons to adapt to genetic and environmental perturbations and evoke a 'new normal' can be most fully appreciated in the context of neurological disorders in which clinical impairments do not manifest until late in life, although dysfunctional proteins are expressed early in development. We now know that proteins controlling ATP generation, mitochondrial stability, and the redox environment are associated with neurological disorders such as Parkinson's disease and amyotrophic lateral sclerosis. Generally, focus is placed on the role that early or long-term environmental stress has in altering the survival of cells targeted by genetic dysfunctions; however, the central nervous system undergoes several periods of intense stress during normal maturation. One of the most profound periods of stress occurs when 50% of neurons are removed via programmed cell death. Unfortunately, we have virtually no understanding of how these events proceed in individuals who harbor mutations that are lethal later in life. Moreover, there is a profound lack of information on circuit formation, cell fate during development and neurochemical compensation in either humans or the animals used to model neurodegenerative diseases. In this review, we consider the current knowledge of how energetic and oxidative stress signaling differs between neurons in early versus late stages of life, the influence of a new group of proteins that can integrate cell stress signals at the mitochondrial level, and the growing body of evidence that suggests early development should be considered a critical period for the genesis of chronic neurodegenerative diseases.