Quartz Tuning Fork Research Articles

Highly sensitive detection of methane based on LITES and H-LITES techniques

In this paper, a highly sensitive methane (CH4) sensor utilizing light-induced thermoelastic spectroscopy (LITES) and heterodyne light-induced thermoelastic spectroscopy (H-LITES) techniques was developed for the first time. The sensor employed a quartz tuning fork (QTF) with a resonance frequency (f0) of 32762.80 Hz and a quality factor (Q) of 12009.824 as the detector. A continuous wavelength distributed feedback (CW-DFB) diode laser emitting at 1650.96 nm with a maximum output power of 30 mW was used for strong exciting of the target gas. Detailed testing was conducted to assess the sensor’s performance. The results revealed that both CH4-LITES and CH4-H-LITES sensors had excellent linearity concentration response. The minimum detection limit (MDL) for these two sensors was found to be 5.402 ppm and 9.742 ppm, respectively. Compared to CH4-LITES sensor, CH4-H-LITES had the ability to acquire the heterodyne signal and identify the f0 of QTF in just 2 s, showing a fast response capability.

Quasi-distributed quartz enhanced photoacoustic spectroscopy sensing based on hollow waveguide micropores.

In this Letter, a quasi-distributed quartz enhanced photoacoustic spectroscopy (QEPAS) gas sensing system based on hollow waveguide micropores (HWGMP) was reported for the first time, to the best of our knowledge. Three micropores were developed on the HWG to achieve distributed detection units. Three self-designed quartz tuning forks (QTFs) with low resonant frequency of 8.7 kHz were selected as the acoustic wave transducer to improve the detection performance. Compared with micro-nano fiber evanescent wave (FEW) QEPAS, the HWGMP-QEPAS sensor has advantages such as strong anti-interference ability, low loss, and low cost. Acetylene (C2H2) was selected as the target gas to verify the characteristics of the reported sensor. The experimental results showed that the three QTFs almost had the same sensing ability and possessed an excellent linear concentration response to C2H2. The minimum detection limits (MDLs) for the three QTFs were determined as 68.90, 68.31, and 66.62 ppm, respectively. Allan deviation analysis indicated that the system had good long-term stability, and the MDL can be improved below 3 ppm in an average time of 1000 s.

Sensitive detection of low doses beta particles using quartz crystal oscillators

The demand for developing a cheap and novel ionizing radiation detection technique has recently increased. This work aims to establish a new detection method for beta particles based on a quartz tuning fork (QTF). QTF coated and uncoated with 40 nm of aluminum (Al) were used to evaluate the system under different conditions. All samples were exposed to different doses of beta using a 90Sr beta source. The results confirmed that a clear frequency shift was observed during beta irradiation. Once the radiation source was removed, the frequency returned to normal behavior. This effect is more pronounced with the Al-coated sample due to more tensile stress caused by thermal heating induced by beta radiation. Before and after beta irradiation, the optical properties of SiO2 wafers (quartz) were also studied using spectroscopic ellipsometry (SE) measurements. The SE results were largely consistent with the QTF resonance frequency shift results. In conclusion, experiment results proved the probability of using QTF as sensitive, accurate, and easy-to-use sensing for low-dose beta radiation.

Design, fabrication, and evaluation of a novel highly sensitive tuning fork pressure sensor for precise liquid level measurement

This article investigates the under-explored potential of utilizing a thin stainless-steel diaphragm coupled with a quartz tuning fork sensor for liquid depth measurements. The focus is on monitoring molten salt fluid levels in nuclear reactors and concentrated solar power systems. Addressing a literature gap, the research explores cantilever-type configurations of a double-ended quartz tuning fork resonator, with a no-load resonance frequency of 17.37 kHz, on thin stainless-steel diaphragms for fluid depth measurement at room temperature. As the fluid depth increases, hydro-static pressure acting on a 20 μm diaphragm causes deflection, bending a tuning fork. The resulting change in resonance frequency correlates with fluid depth. Experimental setups assess the tuning fork’s sensitivity to strain and bending, revealing strain sensitivity of 7.83 Hz/μ strain (450.78 ppm/μ strain) and bending sensitivity of 0.09 Hz/μm (5.18 ppm/μm). The pressure sensor assembly, tested in a water tank, exhibits a sensitivity of −0.28 Hz/mm (−16.12 ppm/mm) in a single cantilever-type configuration. Despite a limited linear range, it effectively measures water depth changes as small as 0.7 mm. Exploring a double cantilever-type configuration yields a sensitivity of 0.07 Hz/mm (4.03 ppm/mm) with a broader linear range. The article discusses the reasons for opposite sensitivity and highlights the advantages of each configuration. Beyond molten salt level monitoring, the technology’s applications may extend to fluid depth and pressure measurements in industrial and domestic settings.

Rapid standoff spectroscopic characterization of plastic waste using quartz tuning fork

Standoff molecular identification of chemicals finds immense applications in homeland security, forensic investigation and plastic recycling industries. Although, standoff detection using mid-infrared radiation offers excellent molecular selectivity, sensitive detection of mid-IR radiation using inexpensive detectors is a challenge. In the present work, we show commercially available inexpensive Quartz Tuning Fork (QTF) can be effectively used for rapid standoff detection of solid samples using mid-IR radiation. In this method, a plastic sample placed 40 cm away was excited with tunable infrared (IR) radiation pulsed at the resonance frequency of the QTF. The IR radiation scattered off the plastic sample was used for exciting the QTF into resonance. Plotting the QTF resonant amplitude as a function of irradiating IR wavelength represents the unique IR spectrum of the plastic sample under study. The resolution of spectra recorded using QTF was found to be superior to those collected with ATR-FTIR and the technique based on QTF was 103 times faster than microcantilever-based photothermal deflection techniques. By combining simple machine learning algorithms with QTF standoff resonance IR spectra, various plastic samples can be effectively classified with 100% accuracy. Also, this technique was found to be capable of identifying black plastics without any further sample preparation requirements.

Two-dimensional analysis of the interfacial solvation structure of an ionic liquid electrolyte on a hydrogen-terminated Si electrode by atomic force microscopy

Ionic liquids (ILs) have been intensively studied as new electrolytes for lithium-ion batteries (LIBs). Structural analysis of interfaces between an IL-based electrolyte and an LIB electrode would provide beneficial information for improving LIBs. In this study, we investigated the interfacial structures between an IL, 1-methyl-1-propyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide, and a H-terminated Si(111) electrode in the presence and absence of Li salt by frequency modulation atomic force microscopy utilizing a quartz tuning fork sensor. Two-dimensional frequency shift mapping imaging of the solvation structure at the interface showed that the layered solvation structure was only observed in the absence of Li salts in the ILs, which was in good agreement with our previous studies performed on IL/lithium titanate interfaces. Combined with electrochemical measurements, the partial disappearance of the layered solvation structure in the Li salt-doped IL was strongly suggested to be due to the Li-ion insertion/extraction at the IL/Si interface.

Design of a Transformer Oil Viscosity, Density, and Dielectric Constant Simultaneous Measurement System Based on a Quartz Tuning Fork.

Transformer oil, crucial for transformer and power system safety, demands effective monitoring. Aiming to address the problems of expensive and bulky equipment, poor real-time performance, and single parameter detection of traditional measurement methods, this study proposes a quartz tuning fork-based simultaneous measurement system for online monitoring of the density, viscosity, and dielectric constant of transformer oil. Based on the Butterworth-Van Dyke quartz tuning fork equivalent circuit model, a working mechanism of transformer oil density, viscosity, and dielectric constant was analyzed, and a measurement model for oil samples was obtained. A miniaturized simultaneous measurement system was designed based on a dedicated chip for vector current-voltage impedance analysis for data acquisition and a Savitzky-Golay filter for data filtering. A transformer oil test platform was built to verify the simultaneous measurement system. The results showed that the system has good repeatability, and the measurement errors of density, viscosity, and dielectric constant are lower than 2.00%, 5.50%, and 3.20%, respectively. The online and offline results showed that the system meets the requirements of the condition maintenance system for online monitoring accuracy and real-time detection.

Functionalization of quartz tuning fork sensor with a thin layer of dopamine for enhanced sensitivity

Quartz tuning fork (QTF) sensors are widely used in various sensing applications due to their high sensitivity, stability, and accuracy. This study explores the functionalization of QTF sensors with a thin coating of polydopamine which can be used a molecular receptor for specific analytes. Dopamine is a neurotransmitter that plays a critical role in the brain's reward and pleasure centers, has been shown to have unique chemical and physical properties that make it a valuable functionalization agent for sensing applications. The functionalized QTF sensors were characterized using measurements of their resonance frequency which is an indication of coated mass of dopamine on the individual prongs of the QTF sensors. Additionally, the coatings were characterized through scanning electron microscopy and Fourier-transform infrared spectroscopy. The performance of the functionalized sensors was evaluated by measuring their response to various thickness of the polydopamine coating.

Quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy

The extension of dual-comb spectroscopy (DCS) to all wavelengths of light along with its ability to provide ultra-large dynamic range and ultra-high spectral resolution, renders it extremely useful for a diverse array of applications in physics, chemistry, atmospheric science, space science, as well as medical applications. In this work, we report on an innovative technique of quartz-enhanced multiheterodyne resonant photoacoustic spectroscopy (QEMR-PAS), in which the beat frequency response from a dual comb is frequency down-converted into the audio frequency domain. In this way, gas molecules act as an optical-acoustic converter through the photoacoustic effect, generating heterodyne sound waves. Unlike conventional DCS, where the light wave is detected by a wavelength-dependent photoreceiver, QEMR-PAS employs a quartz tuning fork (QTF) as a high-Q sound transducer and works in conjunction with a phase-sensitive detector to extract the resonant sound component from the multiple heterodyne acoustic tones, resulting in a straightforward and low-cost hardware configuration. This novel QEMR-PAS technique enables wavelength-independent DCS detection for gas sensing, providing an unprecedented dynamic range of 63 dB, a remarkable spectral resolution of 43 MHz (or ~0.3 pm), and a prominent noise equivalent absorption of 5.99 × 10-6 cm-1·Hz-1/2.

Compact Viscosity Sensors for Downhole Enhanced Oil Recovery Polymer Fluid Degradation Monitoring

Summary There are currently no technologies available to measure polymer solution viscosities at realistic downhole conditions in a well during enhanced oil recovery (EOR). In this paper, custom-made probes using quartz tuning fork (QTF) resonators are demonstrated for measurements of viscosity of polymer fluids in the laboratory. The electromechanical response of the resonators was calibrated in simple Newtonian fluids and in non-Newtonian polymer fluids at different concentrations. The responses were then used to measure field-collected samples of polymer injection fluids. In the polymer fluids, the measured viscosity values by tuning forks were lower than those measured by the conventional rheometer at 6.8 s−1, closer to the solvent viscosity values. However, the predicted rheometer viscosity vs. QTF-measured viscosity showed a distinct exponential correlation (R2=0.9997), allowing for an empirical calibration between the two viscometers for fluids having the same solvent and polymer compositions. The QTF sensors produced acceptable viscosity measurements of polymer fluids within the required polymer concentration ranges used in the field and predicted field sample viscosities with less than 1–2 cp (or 10–20%) error from the rheometer data. Results were validated based on separate independent tests where the devices were used to measure the viscosity of Newtonian fluids and non-Newtonian polymer fluids in a series of consecutive dip tests, simulating more realistic usage. These devices can be used to measure either the “relative” viscosity changes from a polymer solution prior and post-injection or to measure a “calibrated” viscosity via empirical exponential correlation. The compact QTF sensors developed in this study can be easily integrated into portable systems for laboratory or wellsite deployment as well as logging tools for downhole deployment. This work also demonstrates the ability of these QTF devices to make sensitive viscosity measurements at high-frequencies, opening opportunities for their use in high-frequency rheology studies of EOR fluids.

Influence of the Gain–Bandwidth of the Front-End Amplifier on the Performance of a QEPAS Sensor

The quartz tuning fork used as an acoustic sensor in quartz-enhanced photo-acoustic spectroscopy gas detection systems is usually read out by means of a transimpedance preamplifier based on a low-noise operational amplifier closed in a feedback loop. The gain–bandwidth product of the operational amplifier used in the circuit is a key parameter which must be properly chosen to guarantee that the circuit works as expected. Here, we demonstrate that if the value of this parameter is not sufficiently large, the response of the preamplifier exhibits a peak at a frequency which does not coincide with the series resonant frequency of the quartz tuning fork. If this peak frequency is selected for modulating the laser bias current and is also used as the reference frequency of the lock-in amplifier, a penalty results in terms of signal-to-noise ratio at the output of the QEPAS sensor. This worsens the performance of the gas sensing system in terms of ultimate detection limits. We show that this happens when the front-end preamplifier of the quartz tuning fork is based on some amplifier models that are typically used for such application, both when the integration time of the lock-in amplifier filter is long, to boost noise rejection, and when it is short, in order to comply with a relevant measurement rate.

Highly sensitive and reversible MXene-based micro quartz tuning fork gas sensors with tunable selectivity

Due to their distinctive morphology, significant surface-to-volume ratio, and metal-like electrical conductivity, MXenes have emerged as highly promising gas-sensing materials. Traditional MXene-based gas sensors predominantly rely on the electrical conductivity of MXenes for signal transduction. However, it is crucial to explore alternative signal transduction mechanisms to fully unlock the potential of MXenes in gas sensing applications. In this study, we have successfully showcased the development of a mass-transduction-based MXene gas sensor, utilizing MXenes as the adaptable receptor and MQTF as the transducer. The interaction between the gas analyte and MXenes induces a change in mass, resulting in a resonant frequency shift of the MQTF. This signal transduction mechanism eliminates the dependency on the electrical conductivity of MXenes, offering a broader range of possibilities for chemical modification of MXenes without concerns about compromising their conductivity. By engineering Ti3C2Tx surfaces, we have demonstrated high sensitivity and selectivity tuning of MXene-MQTF gas sensors for detecting CO, SO2, and NH3. This antisymmetric mass-transduction-based (low-cost, stable, sensitive, and practical tuning fork-based) MXene gas sensor demonstrated exceptional sensing performance, customizable selectivity, and high cost-effectiveness. This study paves the way for designing high-performance MXene-based chemical sensors and expands the scope of potential applications in air quality monitoring, wearable devices, the Internet of Things (IoT), and robotics.

Quartz-enhanced photoacoustic spectroscopy sensing using trapezoidal- and round-head quartz tuning forks.

In this Letter, two novel, to the best of our knowledge, quartz tuning forks (QTFs) with trapezoidal-head and round-head were designed and adopted for quartz-enhanced photoacoustic spectroscopy (QEPAS) sensing. Based on finite element analysis, a theoretical simulation model was established to optimize the design of QTF. For performance comparison, a reported T-head QTF and a commercial QTF were also investigated. The designed QTFs have decreased resonant frequency (f0) and increased gap between the two prongs of QTF. The experimentally determined f0 of the T-head QTF, trapezoidal-head QTF, and round-head QTF were 8690.69 Hz, 9471.67 Hz, and 9499.28 Hz, respectively. The corresponding quality (Q) factors were measured as 11,142, 11,411, and 11,874. Compared to the commercial QTF, the resonance frequencies of these QTFs have reduced by 73.45%, 71.07%, and 70.99% while maintaining a comparable Q factor to the commercially mature QTF. Methane (CH4) was chosen as the analyte to verify the QTFs' performance. Compared with the commercial QTF, the signal-to-noise ratio (SNR) of the CH4-QEPAS system based on the T-head QTF, trapezoidal-head QTF, and round-head QTF has been improved by 1.75 times, 2.96 times, and 3.26 times, respectively. The performance of the CH4-QEPAS sensor based on the QTF with the best performance of the round-head QTF was investigated in detail. The results indicated that the CH4-QEPAS sensor based on the round-head QTF exhibited an excellent linear concentration response. Furthermore, a minimum detection limit (MDL) of 0.87 ppm can be achieved when the system's average time was 1200 s.

Molecularly Imprinted Chitosan Modified Quartz Tuning Fork Sensors for Real Time Biosensing in Liquid Environment

Several new sensing technologies have emerged to meet the escalating demand for accurate and rapid diagnosis. We present an overview of the development of highly sensitive and selective Quartz Tuning Fork (QTF)-based sensors in a liquid environment, which will be critically important for contemporary diagnostic methods reliant on sensing technologies. The purpose of this study is to modify QTF prongs using molecularly imprinted chitosan, in combination with the operation of a quartz tuning fork as a piezoelectric crystal for biomedical applications. Through real-time data acquisition, we evaluate QTF resonance frequency shifts in dry and liquid environments using a model protein, BSA. As a result, the QTF-based sensor fails to detect BSA in dry conditions. It is however possible to measure frequency shifts ranging from 5 to 25 µg /mL within a liquid matrix. There is a rapid equilibration response time of 2 to 10 minutes depending on the concentration of BSA in the sensor. With the developed QTF-based sensor, a sensitivity of 1.1069 Hz/ µg has been achieved within the liquid matrix. As a result of the excellent properties of molecularly imprinted chitosan, it has been possible to develop a QTF-based biosensor capable of acquiring real-time data even when it is in liquid solutions.

High-sensitivity methane detection based on QEPAS and H-QEPAS technologies combined with a self-designed 8.7 kHz quartz tuning fork

Methane (CH4) is a greenhouse gas as well as being flammable and explosive. In this manuscript, quartz-enhanced photoacoustic spectroscopy (QEPAS) and heterodyne QEPAS (H-QEPAS) exploring a self-designed quartz tuning fork (QTF) with resonance frequency (f0) of ∼8.7 kHz was utilized to achieve sensitive CH4 detection. Compared with the standard commercial 32.768 kHz QTF, this self-designed QTF with a low f0 and large prong gap has the merits of long energy accumulation time and low optical noise. The strongest line located at 6057.08 cm−1 in the 2v3 overtone band of CH4 was chosen as the target absorption line. A diode laser with a high output power of > 30 mW was utilized as the excitation source. Acoustic micro-resonators (AmRs) were added to the sensor architecture to amplify the intensity of acoustic waves. Compared to the bare QTF, after the addition of AmRs, a signal enhancement of 149-fold and 165-fold were obtained for QEPAS and H-QEPAS systems, respectively. The corresponding minimum detection limits (MDLs) were 711 ppb and 1.06 ppm for QEPAS and H-QEPAS sensors. Furthermore, based on Allan variance analysis the MDLs can be improved to 19 ppb and 27 ppb correspondingly. Compared to the QEPAS sensor, the H-QEPAS sensor shows significantly shorter measurement timeframes, allowing for measuring the gas concentration quickly while simultaneously obtaining f0 of QTF.

Evanescent wave quartz-enhanced photoacoustic spectroscopy employing a side-polished fiber for methane sensing

We present an all-fiber-based laser gas analyzer (LGA) employing quartz-enhanced photoacoustic spectroscopy (QEPAS) and a side-polished fiber (SPF). The LGA comprises a custom quartz tuning fork (QTF) with 0.8 mm prong spacing, two acoustic micro-resonators (mR) located on either side of the prong spacing, and a single-mode fiber containing a 17 mm polished section passing through both mRs and QTF. The SPF polished face is positioned to enable the evanescent wave (EW) to create a photoacoustic wave and excite the fundamental flexural mode of the QTF. Sensor performance was demonstrated using methane in nitrogen gas mixtures, with CH4 mixing ratios ranging from 75 ppmv to 1% (by volume), measured with an accumulation time of 300 ms, and a minimum detection limit of 34 ppmv subsequently determined. The EW-QEPAS sensor is ideal for miniaturization, as it does not contain any free-space optics and is suitable for gas sensing in harsh environments and where mobility is required.

A novel colorimetric tuning fork sensor for ammonia monitoring

In this work, we reported the design and performance of a novel colorimetric tuning fork (CTF)-based gas sensor that could simultaneously capture both chemical and mechanical information of the same sensing event. The CTF sensor could transduce optical signals from a colorimetric reaction and frequency signals from the mass change. By transducing 2-dimensional (2D) sensing signals on the same CTF sensing unit, different aspects of physicochemical properties could provide a rich spectrum of binding events, leading to more accurate, sensitive, and reproducible gas detection. We demonstrated the CTF-based 2D sensing concept by coating bromophenol blue on the prongs of a micro quartz tuning fork (MQTF) as the receptor for ammonia detection. Our test results exhibit CTF ammonia sensor could reversibly detect ammonia in the air over a wide range (500 ppb - 1000 ppm) with a detection limit of 500 ppb and excellent selectivity. Due to its small size (a few millimeters), low cost (less than $1), simple fabrication process, and high performance, the CTF sensor could serve as an excellent chemical sensing unit for wearables and point-of-care screening tools.

Simultaneous dual-harmonic detection for LITES with a multi-pass configuration based on combined flexural modes of a quartz tuning fork

The simultaneous dual-harmonic detection for light-induced thermoelastic spectroscopy (LITES) with a multi-pass configuration based on combined flexural modes of a quartz tuning fork (QTF) is demonstrated. To enhance the photothermal energy absorbed by a custom QTF, the laser beam is designed to pass through the QTF multiple times. With dual-frequency modulation methodology, the second harmonic (2f_fun) signal and the first harmonic (1f_ove) signal are simultaneously inspired at resonant frequencies of fundamental and overtone flexural modes of the QTF, respectively. Thus, precise light intensity and gas concentration can be retrieved concurrently with corresponding 1f and 1f-normalized 2f signals using frequency division multiplexing technology. In comparison to traditional LITES under the same condition sensor, our triple-pass configuration performs 1.84 times better in signal-to-noise ratio (SNR). According to Allan variance analysis, 1f-normalized 2f signal enables a longer integration time of 1100 s and a lower detection limit of 0.07 ppm. The corresponding normalized noise equivalent absorption coefficient (NNEA) is 0.8 × 10−9 cm−1W/Hz1/2.

A laterally sensitive quartz vibrating beam accelerometer for inertial navigation application

To improve the sensitivity and stability of a quartz vibrating beam accelerometer (QVBA), a laterally sensitive structure was developed that utilizes the force-frequency characteristics of a quartz double-ended tuning fork (DETF) to realize quasi-digital measurement of acceleration. Two DETFs were purposely designed for the sidewalls of the proof mass, and the hinge of the spring-mass structure was along the proof-mass thickness, which improved the sensitivity. Laterally sensitive structures can also solve the fabrication problems of hinges, including accuracy, deformation, and residual stress. A femtosecond laser was used to release the anchor between the out-of-frame and the proof mass to protect the hinge. The isolation structure was designed to float both the DETFs and hinge to reduce the interference of external stress. Electrodes were deposited on the four surfaces of the vibrating beam in a three-segment configuration to excite the DETF into the antiphase in-plane vibration model. As a result, an accelerometer prototype is fabricated, and the performance characterization results exhibit the sensitivity and stability of 188.61 Hz/g and 7.81 ppm, respectively, and the bias instability (Allan deviation) of 1.26 μg, which proves the design rationality of laterally sensitive QVBA.

An innovative method for the detection of alpha synuclein, a potential biomarker of Parkinson's disease: quartz tuning fork-based mass sensitive immunosensor design.

An innovative biosensing fabrication strategy has been demonstrated for the first time using a quartz tuning fork (QTF) to develop a practical immunosensor for sensitive, selective and practical analysis of alpha synuclein protein (SYN alpha), a potential biomarker of Parkinson's disease. Functionalization of gold-coated QTFs was carried out in 2 steps by forming a self-assembled monolayer with 4-aminothiophenol (4-ATP) and conjugation of gold nanoparticles (AuNPs). The selective determination range for SYN alpha of the developed biosensor system is 1-500 ng mL-1 in accordance with the resonance frequency shifts associated with a limit of detection of 0.098 ng mL-1. The changes in surface morphology and elemental composition were evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDX). The remarkable point of the study is that this QTF based mass sensitive biosensor system can capture the SYN alpha target protein in cerebrospinal fluid (CSF) samples with recoveries ranging from 92% to 104%.