8.3 Fiber optic biosensors and lab-on-a-chip devices
2 min read•august 9, 2024
Fiber optic biosensors use light to detect biological molecules. They rely on and evanescent waves to sense changes in the surrounding environment. These sensors offer high and can be used for real-time, label-free detection of various biomolecules.
Lab-on-a-chip devices miniaturize lab processes onto a single chip. They integrate with optical sensing, allowing for rapid, low-volume analysis. These devices enable multiplexed detection and are ideal for point-of-care diagnostics and portable biosensing applications.
Fiber Optic Sensing Principles
Structure and Transmission of Optical Fibers
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- Optical fiber consists of a core, cladding, and protective outer jacket
- Core transmits light signals through total internal reflection
- Cladding surrounds the core with a lower refractive index material
- Total internal reflection occurs when light strikes the core-cladding interface at an angle greater than the critical angle
- Critical angle depends on the refractive indices of the core and cladding materials
- Fiber Bragg grating incorporates periodic variations in the core's refractive index
- Fiber Bragg grating reflects specific wavelengths while allowing others to pass through
Evanescent Wave Phenomena in Fiber Optics
- Evanescent wave forms at the interface between core and cladding during total internal reflection
- Evanescent wave penetrates a short distance into the cladding (typically 100-200 nm)
- Intensity of evanescent wave decays exponentially with distance from the interface
- Evanescent wave interacts with surrounding medium, enabling sensing applications
- Sensitivity of evanescent wave sensors depends on penetration depth and interaction length
- Tapered fibers or D-shaped fibers can enhance evanescent wave sensing by increasing the exposed core area
Lab-on-a-Chip Technology
Microfluidic Principles and Fabrication
- Microfluidics involves manipulating small volumes of fluids (nanoliters to picoliters) in microscale channels
- Lab-on-a-chip devices integrate multiple laboratory functions on a single chip
- reduces sample volume, reagent consumption, and analysis time
- Fabrication techniques include photolithography, soft lithography, and 3D printing
- Common materials for microfluidic devices include glass, silicon, and polymers (PDMS)
- Microfluidic channels typically range from 10 to 100 micrometers in width
Integration of Optics and Multiplexing in Lab-on-a-Chip Devices
- Integrated optics incorporate optical components directly onto the chip
- On-chip waveguides guide light for sensing and detection purposes
- Multiplexing allows simultaneous analysis of multiple analytes or samples
- Spatial multiplexing uses different regions of the chip for parallel measurements
- Spectral multiplexing employs different wavelengths for multiple analyte detection
- Time-division multiplexing sequences measurements to analyze multiple samples
- Integration of optical sensing with microfluidics enables real-time monitoring of reactions and separations
Key Terms to Review (18)
Bioreceptors: Bioreceptors are biological molecules or structures that can specifically recognize and bind to target analytes, such as proteins, nucleic acids, or small molecules. They play a crucial role in biosensors by providing the specificity needed to detect biological and chemical substances, enabling various applications in diagnostics, environmental monitoring, and food safety.
Electrochemical Detection: Electrochemical detection is a method used to identify and quantify substances by measuring the electrical signals generated during chemical reactions. This technique relies on the principles of electrochemistry, where the interaction of analytes with electrodes produces measurable changes in current or potential. It plays a vital role in biosensors and lab-on-a-chip devices, providing sensitive and selective analysis of biochemical substances.
Environmental Monitoring: Environmental monitoring is the systematic collection and analysis of data regarding environmental conditions, including air, water, and soil quality, to assess changes over time and ensure compliance with regulatory standards. This practice plays a crucial role in identifying pollution sources, evaluating ecosystem health, and informing public health decisions. It integrates various technologies and methodologies, including advanced sensors and biosensing techniques, to provide accurate and timely information for environmental management.
Fluorescence sensing: Fluorescence sensing is a technique that utilizes the emission of light from a substance that has absorbed light or other electromagnetic radiation. This method is widely used for detecting and quantifying biological and chemical substances, as it allows for sensitive measurements of molecular interactions and concentrations. Its integration into fiber optic biosensors and lab-on-a-chip devices enhances the capabilities for real-time monitoring and analysis in various applications, particularly in medical diagnostics and environmental monitoring.
High-throughput screening: High-throughput screening (HTS) is a method used to quickly assess a large number of biological samples or compounds for specific activities, such as drug discovery or gene function analysis. This approach employs automation and advanced technologies, allowing researchers to evaluate thousands of samples simultaneously, significantly speeding up the process of identifying promising candidates for further study.
Lab-on-a-chip technology: Lab-on-a-chip technology refers to the miniaturization of laboratory processes onto a single chip, enabling the integration of multiple functions such as sample preparation, analysis, and detection in a compact format. This technology utilizes microfluidics to control the movement and manipulation of small volumes of fluids, allowing for rapid and efficient biochemical analyses, often with reduced costs and improved sensitivity compared to traditional laboratory methods.
Medical diagnostics: Medical diagnostics refers to the process of determining the nature of a disease or condition through various techniques and tools. This field plays a crucial role in identifying health issues early, guiding treatment plans, and monitoring the progression of diseases. Innovative technologies, such as biosensors and lab-on-a-chip devices, have revolutionized medical diagnostics by enabling rapid and accurate testing from small sample sizes.
Microfluidics: Microfluidics is the science of manipulating and controlling fluids at a microscale, typically involving channels with dimensions ranging from tens of micrometers to a few millimeters. This technology allows for the precise handling of small volumes of fluids, enabling advancements in various fields such as diagnostics, biological research, and drug development. By integrating microfluidics with other technologies, it becomes possible to create compact and efficient systems for analyzing biological samples and conducting chemical reactions.
Miniaturization: Miniaturization refers to the process of designing and producing devices and systems at a smaller scale while maintaining their functionality and performance. This concept is particularly important in developing advanced technologies that enhance portability, efficiency, and integration in various applications, especially in biomedical fields like biosensors and lab-on-a-chip devices.
Nanomaterials: Nanomaterials are materials that have structural components at the nanoscale, typically defined as having dimensions between 1 and 100 nanometers. These materials often exhibit unique physical and chemical properties due to their size, which can enhance their performance in various applications. Their remarkable characteristics, such as increased surface area, strength, and reactivity, make them particularly valuable in advanced technologies like biosensors and diagnostic devices.
Optical fiber immunosensor: An optical fiber immunosensor is a biosensing device that utilizes optical fibers to detect specific biological molecules through immunoassays. These sensors leverage the unique properties of optical fibers, such as light transmission and interaction with biomolecules, to provide sensitive and real-time measurements of target analytes, often in a compact format that facilitates integration into lab-on-a-chip devices.
Optical fibers: Optical fibers are thin strands of glass or plastic that transmit light signals over long distances with minimal loss. They enable high-speed data transmission and are crucial in various applications such as medical imaging, biosensing, and neurobiology, serving as the backbone for technologies like OCT and optogenetics.
PCR amplification: PCR amplification, or Polymerase Chain Reaction amplification, is a molecular biology technique used to rapidly make millions of copies of a specific DNA segment. This process is essential for various applications, allowing researchers to analyze small amounts of DNA, detect genetic mutations, or clone genes. The ability to amplify DNA efficiently makes it a powerful tool in diagnostics, forensic analysis, and biological research.
Point-of-care testing: Point-of-care testing refers to medical diagnostic tests that are performed at or near the site of patient care, allowing for immediate results and decision-making. This approach contrasts with traditional lab testing, which often involves sending samples to a laboratory for analysis, resulting in delayed results. Point-of-care testing is significant because it enhances patient management by facilitating rapid diagnosis and treatment, especially in critical situations.
Selectivity: Selectivity refers to the ability of a system or device to distinguish between different types of molecules, signals, or reactions while minimizing interference from others. This characteristic is crucial for enhancing the accuracy and efficiency of various applications, particularly in fields like medical diagnostics and environmental monitoring. High selectivity ensures that a process specifically targets the desired analyte, allowing for reliable results in complex mixtures.
Sensitivity: Sensitivity refers to the ability of a biosensing system to detect small amounts of a target biomarker or analyte within a sample. High sensitivity is crucial for ensuring that even low concentrations of biomarkers can be reliably identified, which is essential for accurate diagnostics and monitoring. This concept is particularly important in various applications where early detection can significantly impact treatment outcomes and patient care.
Spectroscopy: Spectroscopy is a technique used to measure and analyze the interaction between light and matter, helping to identify substances based on their light absorption, emission, or scattering characteristics. It plays a crucial role in understanding various biological and chemical processes, making it essential in areas like medical diagnostics, material science, and environmental monitoring.
Surface plasmon resonance biosensor: A surface plasmon resonance (SPR) biosensor is a highly sensitive optical device that detects biomolecular interactions in real time by measuring changes in refractive index near a sensor surface, typically a metal film. This technology relies on the excitation of surface plasmons—coherent oscillations of free electrons at the interface between a metal and a dielectric—resulting in changes in light reflectivity that correlate with molecular binding events. SPR biosensors are integral to fiber optic biosensors and lab-on-a-chip devices, enabling rapid and precise detection of various analytes without the need for labeling.