Taste the Future: Novel E-Tongue Revolutionizes Liquid Sample Detection

By Dr Silpaja Chandrasekar, PhDReviewed by Susha Cheriyedath, M.Sc.May 17 2024

In a paper published in the journal Microsystems & Nanoengineering, researchers introduced a novel electronic tongue (E-tongue) design, leveraging advanced triboelectric components to create the multichannel triboelectric bioinspired E-tongue (TBIET). This innovative platform, engineered on a single glass slide chip, overcame traditional E-tongues' size and power limitations.

The TBIET exhibited exceptional taste classification accuracy by fusing multiple sensory signals validated across medical, environmental, and beverage samples. With its high reliability and rapid analysis capabilities, the self-powered portable prototype represents a significant advancement for on-site liquid sample detection.

Background

Previous research explored E-tongues, using nonselective sensors and artificial intelligence (AI) to replicate taste perception and analyze flavors. Yet, traditional E-tongues, relying on electrochemical methods, are bulky and require large sample volumes.

Triboelectric nanogenerators (TENGs) offer self-powering and miniaturization, facilitating liquid sensing like droplet detection. Integrating triboelectric principles into E-tongues provides benefits such as self-powering and reduced sample volumes. While effective, prior droplet triboelectric responses lack practicality, prompting the need for multichannel triboelectric E-tongues for real-world use.

TBIET Classification Study

The study encompassed the preparation of various liquid samples to evaluate the classification capacity of the TBIET system. These samples included chemical solutions, environmental samples, and food samples, each prepared to specific concentrations for testing purposes.

Additionally, NaCl solutions were ready to assess the TBIET's classification capability across different concentration levels. The TBIET device's fabrication process involved assembling four distinct layers: a glass substrate, a metal electrode, a PDMS buffer layer, and a triboelectric film. Each layer was meticulously prepared and assembled to ensure the optimal functioning of the device.

The analysts characterized the TBIET device using a comprehensive setup involving mounting the device on a 3D-printed bracket at a specific angle to facilitate droplet deposition. The spatial orientation of the dropper relative to the device was adjusted using graduated sliders, ensuring consistent droplet placement.

The output signals from the TBIET were processed using three different algorithms—linear discriminant analysis (LDA), support vector machine (SVM), and random forest (RF)—implemented in Python. These algorithms facilitated studying acquired data and classifying samples based on their unique signal patterns.

The work mechanism of the TBIET device was elucidated, detailing its operational phases and charge transfer processes during droplet deposition. Computational simulations were performed to visualize the potential liquid distribution and charge transfer dynamics across the triboelectric sensors. Theoretical models describing charge distribution and transfer between solids and liquids were employed to understand the underlying principles governing the TBIET's functionality. Additionally, AI methods were utilized to analyze signal variances and enhance the device's classification capability, inspired by biomimicry and leveraging diverse film materials for comprehensive sample analysis.

Overall, the study provided a comprehensive overview of the materials and methods employed in developing and characterizing the TBIET device, elucidating its operational principles and classification capabilities through experimental and computational analyses.

TBIET Data Analysis

The study begins by outlining the process flow for data collection, preparation, and classification of TBIET output signals. Raw data from the TBIET device undergo initial processing to extract relevant feature values, which is crucial for subsequent AI classification.

The data collection phase involves acquiring at least 30 samples for each category, ensuring robust analysis. Sign peaks corresponding to different liquid samples exhibit distinct characteristics, with signal changes attributed to system noise. Visual representations and signal behaviors are analyzed, confirming the reliability of the data.

Detailed processes for data analysis, including identification of local extremum and fusion of signals into eigenvalues, are described. Feature extraction approaches utilizing original data (ORI) and difference data (DIF) are employed to provide input for machine learning algorithms.

LDA is first used for visualization, followed by SVM and RF algorithms for comprehensive classification. Results demonstrate the efficacy of the TBIET device in accurately categorizing chemical, environmental, and food samples, showcasing robust classification capabilities across diverse scenarios.

The study evaluates classification outcomes for various liquid samples, highlighting high accuracy rates achieved by SVM and RF algorithms. Confusion matrices provide detailed insights into classification accuracy across different sample types and concentrations.

Classification accuracies exceeding 92.7% are consistently observed, reinforcing the TBIET's proficiency in sample classification. Notably, fusion of multiple channels significantly enhances classification accuracy, demonstrating the system's effectiveness in categorizing samples with varying concentrations.

A comparative analysis between TBIET and traditional E-tongue systems underscores TBIET's convenience, non-invasive nature, and broad-spectrum responsiveness. The study discusses potential applications in mineral exploration, environmental monitoring, agriculture, and medical diagnostics.

Limitations related to data variability and interference from unknown samples are addressed, suggesting approaches such as microfluidic integration and advanced deep learning models for future enhancement. Overall, the study highlights TBIET's potential for commercial applications and outlines strategies for further overcoming current limitations to improve its functionality and reliability.

Conclusion

In summary, a new triboelectric bioinspired E-tongue integrates liquid-solid power generation with AI for taste-sensing. It features four triboelectric polymer films on a single chip and was tested with various samples, showing over 92.7% classification accuracy. Notably, it achieved 100% accuracy for ion-type solutions and high accuracy for environmental and tea samples. This device marks a significant advancement in liquid sensor technology.