Advanced Sensor Research最新文献

The miniature optical fiber ultrasound sensor with high sensitivity and bandwidth is important for the field of ultrasonic detection. In this study, a unique fiber ultrasound sensor via integrating optical microrings on a multicore fiber facet is reported. The results demonstrate this sensor can be used in liquid environment and has high sensitivity with broadband bandwidth. The detector's equivalent noise pressure (NEP) can reach 13.2 mPa Hz^−1/2 with a broadband ultrasound response over 250 MHz (103 MHz in −6 dB). Besides, this sensor is resistant to environmental impurities. The sensor is successfully applied to photoacoustic microscopy (PAM) with a lateral resolution of 5 µm and an axial resolution of 6.6 µm. Furthermore, an integrated transceiver structure for ultrasound/photoacoustic detection is proposed, which has great application prospects for using in constrained tiny spaces, such as endoscopy, or closely scanning over uneven surfaces.

The use of hydrogen as an energy carrier will require low-cost, low-power hydrogen sensors. Toward this goal, penta-twinned palladium nanowires (Pd NWs) are synthesized and fabricated sensors from them by drop-casting. Pd NWs drop-cast onto an interdigitated electrode (IDE) gave a response of 0.3% to 1 vol.% H₂, with response and recovery times of 12 and 20 s, respectively. However, they exhibited a negative response (decreased resistance) at low H₂ concentrations. Pd NWs on a paper substrate provided a tenfold higher response to 1 vol.% H₂, with response and recovery times of 10 s each, but still exhibited negative response at low H₂ concentration. Exposing the Pd NW-on-paper sensor to ozone-generating UV light degraded the PVP used in Pd NW synthesis, eliminating the reverse sensing response, and providing a response of 5% to 1 vol.% H₂, with response and recovery times of 15 s. This allowed reliable H₂ detection down to 100 ppm H₂. Finally, coating the Pd NWs with a small amount of Pt (<5%) reduced the response and recovery times to 5 s by catalyzing H₂ dissociation. This work provides a path to low-cost sensors to enable the safe use of H₂ as an energy carrier.

Achieving sensitive detection using terahertz (THz) time-domain spectroscopy (TDS) remains challenging due to the low probabilities of molecules being positioned within microscale active regions of typical THz metamaterials. The hybrid metamaterials are prepared with expanded active surface areas by templating CuO nanoflowers into Cu nanoslots through the one-step hydrothermal method. The optimum condition of CuO/Cu nanoslots is achieved with variations in optical transmittance and without alteration of resonance frequency (f_res). The enhancement of detection efficiency is obtained with acetylcholine (ACh), which has a hydrolysis-transformable characteristic. The cleavage of ACh into two molecules, namely choline and acetic acid, poses a challenge for direct THz-TDS detection. This is because the altered molecular energy states do not match with the resonance frequencies of pristine Cu nanoslots. Since the CuO nanoflowers with high chemical reactivity became corroded by acetic acid, sufficient signal variations are observed. As a portion of CuO nanoflowers is decreased, the transmittance gradually reached the original state (i.e., recovery). For the ACh, the comparison of sensing performance (i.e., sensitivity, limit-of-detection, and correlation coefficient) between the CuO/Cu and Cu nanoslots is intensively performed.

Measurements of low-frequency physiological signals, such as heart rate and pulse waves, play an essential role in biomedical applications for the early diagnosis of abnormal cardiovascular activities. Recent advances in flexible mechanical electronics represent a novel concept of miniaturized, wearable sensors for heart rate measurement that can be used in ambulatory environments. However, most mechanical sensors require the sensing element to be placed directly on the skin surface, which can lead to performance degradation or device damage due to significant skin deformation or external forces from skin-object interactions. This work addresses this challenge by developing soft, stretchable mechano-acoustic sensing platforms where all sensing components are not directly subjected to skin movement or deformation. Instead, this design allows cardiovascular pulse waves to propagate through a hollow, flexible microchannel, to vibrate the piezoresistive sensing element. Experimental studies demonstrate a complete wireless sensing system capable of detecting pulse waves and heart rates, with results consistent with those of commercially available devices. The proposed sensing concept allows for the develop of other wireless and flexible sensing systems such as a flexible air-channel pad for detecting swallowing patterns from users’ laryngeal movements, facilitating a non-invasive and remote platform for potential monitoring, and assessment of dysphagia.

Robot-assisted microinjection has been widely implemented in the field of experimental biology research. Force perception is more accurate than visual feedback in determining the state of interaction between the micropipette and the biological sample. The existing micro-force sensors are difficult to directly combine with micropipettes to fully utilize their capabilities. This paper develops a new integrated force-sensing microinjector with both micro-force sensing and micropipette carrying functions using a symmetrical compliant guide mechanism and highly sensitive semiconductor strain gauges. Overload protection is considered in the structure design of the sensor, which is beneficial in reducing damage caused by displacement overshot due to misuse. The mechanical performance of the proposed dual-interval force sensing device is verified through theoretical derivation, simulation analysis, and experimental testing. The sensitivity, resolution, accuracy, dynamic response, stability, and repeatability of the sensor are investigated and evaluated in the established experimental platform. Finally, puncture experiments are conducted on zebrafish larvae and crab eggs using the proposed force-sensing microinjector. The results indicate that the sensor is effective in recording force signals during penetration of the sample.

Coupling surface plasmon resonance (SPR) sensing with electrochemistry (EC) is a promising analytical strategy to obtain information about interfacial phenomena in heterogeneous reactions. Typical EC-SPR sensors utilize a metal film both as the plasmonic material and as the working electrode. In this configuration, the eigenmodulation of the plasmonic properties of the metal film under applied potential results in a background signal, which hampers the unambiguous interpretation of the sensor response due to redox reactions. Here, a new strategy is presented to overcome this disadvantage by using a van der Waals heterostructure (vdW-HS) as the working electrode. The vdW-HS comprises of a graphene / hexagonal boron nitride (hBN) stack on a gold film of a standard SPR sensor. It is shown here that the background signal is completely suppressed enabling the unambiguous analysis of SPR sensor response due to electrochemical reactions. It is further observed that the potential dependent plasmonic signals are not just a reproduction of the electrochemical current and subtle differences can be traced back to the diffusive nature of the redox active species. Finally, it is demonstrated that EC-SPR can be used as a complementary method to distinguish if the electrochemical response is mainly surface-bound or due to diffusion.

Reliable detection of hydrogen (H₂) leakage at low temperatures (e.g., < 273 K) is highly desired in those critical environments that may cause failure in detection, which needs further development. Herein, H₂ sensing that can work at ≈190–388 K temperature range has been developed by integrating palladium and zinc nanowires enwrapped with nanosheets (PdZn NWs) as the sensing materials, which have been prepared via combined anodic aluminum oxide (AAO) template-confined electrodeposition and surface engineering. Typically, as-synthesized PdZn NWs with a diameter of ≈50 nm present rough surfaces, along which abundant pores and fractures have been observed. Beneficially, the PdZn NWs show a lower critical temperature (≈190 K) of the “reverse sensing behavior” than that of pure Pd NWs (287 K), indicating the PdZn NWs are able to work at ≈190–388 K temperature range. Theoretically, such stable H₂ sensing can be attributed to the rough surfaces and chemical composition of PdZn NWs, which facilitates H atoms diffusion and accommodates the expansion of PdHx intermediates. The surface engineering of PdZn NWs may contribute to stable H₂ sensing at low temperatures, which can be applied to other gas-sensing materials working at low temperatures.

Sensors play a crucial role in enhancing the quality of life, ensuring safety, and facilitating technological advancements. Over the past decade, 2D layered materials have been added as new sensing element in addition to existing materials such as metal oxides, semiconductors, metals, and polymers. 2D Layered materials are typically characterized by their single or few-layer thickness and offer a high surface-to-volume ratio, exceptional mechanical strength, and unique electronic attributes. These properties make them ideal candidates for a variety of sensing applications. This review article focused on utilizing 2D layered materials in triboelectric nanogenerators (TENGs) for different sensing applications. The best part of TENG-based sensing is that it is self-powered, so no external power supply is required. The initial part of the review focused on the importance of the 2D layered materials and their innovative integration methods in TENGs. Further, this review discusses various sensing applications, including humidity, touch, force, temperature, and gas sensing, highlighting the impact of 2D layered materials in enhancing the sensitivity and selectivity of TENG sensors. The last part of the review discusses the challenges and prospects of TENG-based self-powered sensors.

Amid the landscape of respiratory health, lung disorders stand out as the primary contributors to pulmonary intricacies and respiratory diseases. Timely precautions through accurate diagnosis hold the key to mitigating their impact. Nevertheless, the existing conventional methods of lungs monitoring exhibit limitations due to bulky instruments, intrusive techniques, manual data recording, and discomfort in continuous measurements. In this context, an unintrusive organic wearable piezoelectric electronic-skin respirometer (eSR) exhibiting a high-sensitivity (385 mV N⁻¹), precise conversion factor (12 mL mV⁻¹), high signal-to-noise ratio (58 dB), and a low limit of detection down to 100 mL is demonstrated, which is perfectly suitable to record diverse breathing signals. To empower the eSR with early diagnosis functionality, self-learning capability is further added by integrating the respirometer with the machine learning algorithms. Among various tested algorithms, gradient boosting regression emerges as the most suitable, leveraging sequential model refinement to achieve an accuracy exceeding 95% in detection of chronic obstructive pulmonary diseases (COPD). From conception to validation, the approach not only provides an alternative pathway for tracking the progression of lung diseases but also has the capability to replace the conventional techniques, with the conformable AI-empowered respirometer.

Chronic kidney disease (CKD) has asymptomatic early stages, whereby early detection is crucial to prevent its complications and progression. Creatinine and cystatin C (cysC) assays are known for assessing kidney function but there are limited point-of-care diagnostics which are rapid, precise, and easy to use. Here, high resistivity silicon conductometric sensors for detection of creatinine and cysC with a 10 min sample incubation is introduced. The sensors provide resistance-based signals that can be quantified and measured wirelessly. The sensors successfully detect creatinine and cysC in both phosphate buffer saline (PBS) and artificial saliva in the nanomolar range, being able to distinguish their critical concentrations at 8.8 and 20 nm, respectively, for diagnosis of early stage of CKD. The detection limit for both creatinine and cysC is determined as 0.01 nm which is more than 500× and 1000× times lower than critical concentrations for the two biomarkers, respectively. Finally, these sensors are incorporated into a battery-free, miniaturized electronic device for wireless biomarker detection as a proof-of-concept demonstration of a point-of-care tool for assessing kidney functionality.