On‐skin sensors can precisely perceive important electrophysiological signals, including electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG). Despite significant advances in the development of soft materials as electrode sensors, data acquisition (DAQ) unit—another indispensable component of on‐skin electronic sensory systems—typically exhibits bulkiness or unimodal sensing, which is detrimental to the portability of the sensory system or the comprehensiveness of the perceived information. Here, a portable and multimodal DAQ unit to tackle these challenges is designed. By assembling the DAQ unit with low‐impedance (<100 Ω) laser‐induced graphene on‐skin electrode sensors, a wireless communication module, a power supply module, and a 3D printed protective shell, the completed sensory system can realize three‐in‐one monitoring of EEG, ECG, and EMG with a light weight of 22 g and a low cost of $25. Moreover, a mobile App is developed to display the perceived electrophysiological signals in real time. Human–machine interface and embedded machine learning are demonstrated using the designed sensory system, indicating its potential applications in artificial intelligence. The success of this inexpensive three‐in‐one portable electronic sensory system sheds light on design, fabrication, and commercialization of multifunctional wearable electronics with wide applications in fitness tracking, medical diagnostics, and human–machine interface.

Electrochemical detection, especially anodic stripping voltammetry (ASV), has been widely used in the detection of heavy metal ions because of its high sensitivity, low detection limit, as well as on-site and real-time detection capability. However, ASV detection typically relies on modified sensors, which complicates the preparation process and introduces contaminants to the tested solutions. Herein, we developed a preconcentration relaxation strategy to improve detection performances of bare sensors without modification. Specifically, in the preconcentration step of ASV, the solution stirring did not run throughout the whole preconcentration process but stopped before the end of preconcentration, remaining as a relaxation period for metal ions fully depositing. To verify this strategy, we fabricated porous laser-induced graphene sensors without modification to detect lead ions. With the preconcentration strategy, the detection linear range was widened from 30−100 to 1−100 μg•L −1 , and the sensitivity was increased from 0.1362 μA•(μg•L −1 ) −1 to 0.1772 μA•(μg•L −1 ) −1 in 1−5 μg•L −1 and 0.7081 μA•(μg•L −1 ) −1 in 10−100 μg•L −1 . Moreover, the limit of detection reached 0.5 μg•L −1 (S/N = 3). This work sheds light on the accurate and effective detection of heavy metal ions.

they can only perceive portion, along one or two axes, of a stimulus which is normally full of 3D space surrounding the sensors. [10,11] Another limitation is the deficient interface between the 2D sensors and target objects. For instance, health monitoring could be realized by attaching or implanting biomedical sensors to target organs or tissues of the human body. [12] However, it is difficult for traditional 2D sensors to collect accurate vital signals because they cannot conform to the 3D structure of organs or tissues. [13,14] Although this problem can be partially relieved by using flexible 2D sensors, [15] passive adaptation to target objects inevitably results in gaps. [16] Sensors with 3D structures have been developed to overcome these limitations. A 3D cubic sensor generated by selffolding has the ability to gain concentration as well as spatial information (i.e., direction and orientation) of target analytes surrounding the device. [17][18][19] Moreover, a 3D strain sensor fabricated by in situ 3D printing was observed to be compliant with the surface of a breathing porcine lung for continuous mapping of respiration-induced deformation with high 3D spatial resolution. [20] Besides full-space sensing and conformity to targets, compared to 2D counterparts, 3D sensors also possess advantages such as high sensitivity, [21] large specific surface area, [22] multimodal sensing, [23] and so forth.Despite their superiority to 2D sensors, it is challenging to fabricate a sensor with a delicate 3D configuration on a small scale because current micro-nano fabrication technologies are typically performed on planar silicon wafers. [35] Considerable efforts have been made to develop new fabrication methods for 3D sensors, which will be reviewed in this paper. According to the criterion of material quantity change, [36] these fabrication methods are divided into four categories: bulk chemical etching (subtractive manufacturing), 3D printing (additive manufacturing), molding (formative manufacturing), and stress-induced assembly (formative manufacturing), as shown in Figure 1. Basic applications or sensing functions (e.g., light, force, electricity, and chemical/gas), advanced applications (e.g., robotics, HMI, health monitoring, and tissue engineering), and strengths over 2D counterparts (high spatial resolution, multimodality, conformity, and high sensitivity) are illustrated for relevant 3D sensors. The fabrication methods and their pros and cons in generating 3D structures for various applications are summarized in Table 1. The discussions are concluded by outlining current challenges and future opportunities for 3D sensors.The intelligence of modern technologies relies on perceptual systems based on microscale sensors. However, because of the traditional top-down fabrication approaches performed on planar silicon wafers, a large proportion of existing microscale sensors have 2D structures, which severely restricts their sensing capabilities. To overcome these restrictions, over the past few decades, increasing e...

because of its unique properties including high light absorption coefficient, high charge carrier mobility, and large charge carrier diffusion length. [11][12][13] Besides, high-quality perovskite films can be fabricated on a large scale by facile and inexpensive solution methods, which promote mass production of perovskite-based optoelectronics devices. [2,14,15] For example, a slot-die printing technology has been recently developed to continuously fabricate a formamidinium cesium lead triiodide (FACsPbI 3 ) perovskite film as large as 400 cm 2 in one batch. [16] In addition to perovskites for light absorbing and charge carrier generating, electrodes are also indispensable to optoelectronic devices for charge carrier collection. [17,18] Traditionally, noble metals including gold, [19,20] silver, [21,22] and platinum, [23] are used as electrodes for their high conductivity and appropriate work functions. [17] However, these metal electrodes are typically deposited onto the perovskite films by magnetron sputtering or thermal evaporation under extreme conditions (i.e., high temperature and vacuum), [8,18,24] hindering mass production of the perovskite-based optoelectronic devices. Thus, it is crucial to develop new electrodes to realize whole-device mass production.Laser-induced graphene (LIG) is a promising candidate for this purpose. It has been employed as excellent electrodes for various electronic devices, [25][26][27] obtained by direct laser writing (DLW), a mask-free microfabrication technique with low cost and high scalability. [28] The conductivity of LIG electrodes is high [28] while the cost is low because it can be synthesized from multiple carbon sources ranging from commercially available polymer films to agricultural wastes. [29][30][31] Moreover, as a carbon material, LIG would have higher chemical stability than metal materials, which tend to react with lead halide species resulting in device degradation. [17,18,32] So far, LIG electrodes have been demonstrated for large-scale fabrication of microsupercapacitors, [25] wearable humidity sensors, [26] and soil sensors. [27] Therefore, LIG has the potential of serving as electrodes for perovskite-based optoelectronics and realizing whole-device mass production.To conceptually verify this idea, herein, we propose a whole-device mass-producible perovskite photodetector based on LIG electrodes, considering the critical significance of Perovskites have attracted enormous attention in optoelectronics, owing to their excellent optoelectronic properties, low-cost constituents, and simple solution fabrication approaches. Despite significant advances in large-scale production of perovskite films, electrode layers-indispensable components of an optoelectronic device-are typically fabricated by depositing noble metals onto perovskite films using complicated techniques, which hinder the large-scale production of optoelectronic devices. Herein, a whole-device mass-producible perovskite photodetector is developed using low-cost and high-scalability direct laser w...

Wearable sensors have demonstrated wide applications from medical treatment, health monitoring to real-time tracking, human-machine interface, smart home, and motion capture because of the capability of in situ and online monitoring. Data acquisition is extremely important for wearable sensors, including modules of probes, signal conditioning, and analog-to-digital conversion. However, signal conditioning, analog-to-digital conversion, and data transmission have received less attention than probes, especially flexible sensing materials, in research on wearable sensors. Here, as a supplement, this paper systematically reviews the recent progress of characteristics, applications, and optimizations of transistor amplifiers and typical filters in signal conditioning, and mainstream analog-to-digital conversion strategies. Moreover, possible research directions on the data acquisition of wearable sensors are discussed at the end of the paper.