It is shown here that microwave sensors can be used to monitor glucose in serum concentration with minimum detectable as well as resolution of 1 mMol $\cdot \text{L}^{{-1}}$ ( $\approx 18$ mg $\,\cdot $ dL−1). The ultrasensitive detection technique relies on a split ring resonator, operating at the frequency of 1.156 GHz, as the core of the sensor where its loss is compensated to enhance the quality factor from $\sim 190$ (passive mode) to $\sim 3850$ (active mode) to enable high resolution (modified frequency detection error from ±12 kHz down to ±2.5 kHz) frequency-shift sensing. Initially, glucose concentrations of 100–1000 mMol $\,\cdot \text{L}^{{-1}}$ (1800–18000 mg $\,\cdot $ dL−1) in water were detected within 250 kHz of dynamic range (between two spectrum ends). Selectivity of the sensor to glucose is verified with respect to common interstitial fluid ingredients with biological levels. Finally, to enhance the resolution of the proposed sensor, its loss–compensation is further improved leading to increased accuracy of measuring glucose samples in a 0.9 % NaCl solution containing 10 % horse serum that closely resembles blood plasma and interstitial fluid. This allows exploration of lower concentrations in the physiological range 1–30 mMol $\,\cdot \text{L}^{{-1}}$ (18–540 mg $\,\cdot $ dL−1) with improved frequency detection error down to ±0.75 kHz for two cases of with/without serum solutions with dynamic range of 30 kHz/38 kHz. The highly accurate glucose monitoring technique could be utilized for developing noninvasive glucose sensors for biomedical applications in real–time glucose monitoring.

Noninvasive Glucose Sensing in Aqueous Solutions Using an Active Split-Ring Resonator

Wireless electromagnetic detection of non-visible processes is a vital challenge when visual signals are difficult to decipher or blocked, such is the case in pipelines, chemical reactions, or the human body. To guide the design of future microwave resonator sensors, investigative experiments into resonator sensitivity, sensing distance, and RFID array alignment were performed. A horn antenna reader was coupled to a singular flexible ring resonator as well as a flexible ring resonator array with a measured $S_{11}$ notch frequency of 2.6 – 2.9 GHz. The experimental results closely compared to simulation and the computer model illustrated the detection of an introduced material around the high E-field regions of the coupled ring tag. In the fabricated circuit, liquids in a microfluidic channel are detected by a notch frequency and amplitude variation of 300 MHz and −30 dB, respectively, which can be matched with simulations to determine the materials’ permittivity. Other application-based requirements are also investigated such as the sensing range of the antenna-tag structure (measured up to 20 cm), the small size of the sensing tag (9 square cm) and the ability to detect through material barriers.

Passive Split Ring Resonator Tag Configuration for RFID-Based Wireless Permittivity Sensing

Build up of ice and snow can cause major issues in many industrial and academic endeavors if it is not properly detected and addressed. Ice detection systems are commonly based on visual detection and therefore susceptible to human error and environmental conditions. We introduce a microwave resonator sensor fabricated on a planar substrate operating between 3.5–5 GHz with resonant amplitude −14.5 dB and quality factor of 250. The resonator detects water, frost, and ice based on the measured resonant frequency, amplitude, and quality factor variation in scattering parameter, S21, of the sensor. Three situations are investigated to test the effectiveness of the sensor: first, continuous frost formation on the sensor is tracked and the phenomena of water condensation, frost formation, and subsequent frost growth are characterized. Second, a water droplet is placed on the resonator and frozen, enabling faster and more sensitive detection and representing an initial liquid impact or aggregation on a surface followed by freezing. Lastly, controlled frost formation and removal was performed to better understand the effect of substrate temperature on the sensing parameters so that it could be compensated for via calibration.

Robust and sensitive frost and ice detection via planar microwave resonator sensor

In this work, a noninvasive microwave gas sensor suitable for accurate and real-time tracking of volatile organic compounds concentration is presented. The proposed differential sensor was comprised of two independent split-ring resonators in power splitter/combiner configuration to enhance the robustness of the sensor to changes in environmental parameters. The design was fabricated on a Rogers RT/duroid 5880 high-frequency substrate and operated at ${f}_{s}= 5.12$ GHz and ${f}_{r}= 5.65$ GHz, referring to the sensing and reference resonant frequencies, respectively. A thin layer of polydimethylsiloxane was used as an interface layer in the sensing resonator region with the strongest electric field to enable gas sensing with high sensitivity. The performance of the sensor was validated by introducing different volatile organic compounds, such as acetone, methanol, ethanol, and isopropyl alcohol. Time-based responses of the sensor demonstrated the capability of the sensor to monitor different concentrations of acetone vapor ranging from low, 387 to 1935 ppm, with the sensitivity of 0.02 mdB/ppm and high concentrations, 3878 to 62048 ppm, with sensitivity of 0.0125 mdB/ppm.

Differential Microwave Resonator Sensor for Real-Time Monitoring of Volatile Organic Compounds

In this paper, a circular microstrip antenna for stress evaluation is studied. This kind of microstrip sensor can be utilized in structural health monitoring systems. Reflection coefficient S11 is measured to determine deformation/strain value. The proposed sensor is adhesively connected to the studied sample. Applied strain causes a change in patch geometry and influences current distribution both in patch and ground plane. Changing the current flow in patch influences the value of resonant frequency. In this paper, two different resonant frequencies were analysed because in each case, different current distributions in patch were obtained. The sensor was designed for operating frequency of 2.5 GHz (at fundamental mode), which results in a diameter less than 55 mm. Obtained sensitivity was up to 1 MHz/100 MPa, resolution depends on utilized vector network analyser. Moreover, the directional characteristics for both resonant frequencies were defined, studied using numerical model and verified by measurements. Thus far, microstrip antennas have been used in deformation measurement only if the direction of external force was well known. Obtained directional characteristics of the sensor allow the determination of direction and value of stress by one sensor. This method of measurement can be an alternative to the rosette strain gauge.

A Circular Microstrip Antenna Sensor for Direction Sensitive Strain Evaluation.

A planar microstrip ring resonator structure on alumina was developed using the commercial FEM software COMSOL. Design parameters were evaluated, eventually leading to an optimized design of a miniaturized microwave gas sensor. The sensor was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas-sensitive materials under sensor conditions.

Planar Microstrip Ring Resonators for Microwave-Based Gas Sensing: Design Aspects and Initial Transducers for Humidity and Ammonia Sensing.

. Up to now, sensor applications have rarely used materials whose
dielectric properties are a function of the gas concentration. A sensor
principle, by which this material effect can be utilized, is based planar
radio-frequency sensors. For the first time, such a sensor was equipped with
an integrated heater and successfully operated at temperatures up to
700  ∘ C. This makes it possible to apply materials that show
gas-dependent changes in the dielectric properties only at higher
temperatures. By coating the planar resonance structure with a zeolite,
ammonia could be detected. The amount of ammonia stored in the sensitive
layer can thereby be determined, since the resonant frequency of the sensor
shifts with its ammonia loading. Desorption measurements showed a dependence
of the storage behavior of the ammonia in the gas-sensitive layer on the
operating temperature of the sensor. Thus, it was possible that by operating
the sensor at 300  ∘ C, it only shows a gas-concentration-dependent
signal. At lower operating temperatures, on the other hand, the sensor could
possibly be used for dosimetric determination of very low ammonia
concentrations.

https://jsss.copernicus.org/articles/8/49/2019/jsss-8-49-2019.pdf

Novel radio-frequency-based gas sensor with integrated heater

A planar microstrip ring resonator structure on alumina was developed. It was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas sensitive materials under sensor conditions.

https://www.mdpi.com/2504-3900/1/4/414/pdf

Planar Microstrip Ring Resonator Structure for Gas Sensing and Humidity Sensing Purposes

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Andreas Bogner

Author Tools

Chat about Author

Papers

Planar Microstrip Ring Resonators for Microwave-Based Gas Sensing: Design Aspects and Initial Transducers for Humidity and Ammonia Sensing.

Novel radio-frequency-based gas sensor with integrated heater

Planar Microstrip Ring Resonator Structure for Gas Sensing and Humidity Sensing Purposes