Optical Bubble Sensor Using Critical Angle Refraction
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Solution Overview
Problem
Current bubble sensing technologies face challenges in reliably detecting air bubbles in rigid disposable cartridges without complex and expensive loading and coupling mechanisms, particularly in medical fluid management systems where sterility and non-invasive sensing are crucial.
Innovation Solution
An optical bubble sensor employing the critical angle principle, using an optical transmitter to emit light at specific angles for refraction in liquid and reflection in gas, allowing for non-invasive detection through refractive and reflective receivers, which can differentiate between liquid and gas presence in a flow channel without physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic bubble sensors are used in rigid disposable cartridges, then reliable bubble detection can be achieved, but complex and expensive loading and coupling mechanisms are required
Solution Approach 1:
The patent replaces the mechanical ultrasonic coupling system with an optical detection system. Instead of using ultrasonic waves that require intimate contact and complex coupling mechanisms, the invention uses light transmission through the rigid cartridge wall to detect bubbles, eliminating the need for mechanical coupling components.
Solution Approach 2:
The rigid cartridge wall itself serves as an optical intermediary, allowing light to pass through it to detect bubbles inside. This eliminates the need for separate coupling mechanisms while maintaining reliable detection, as the cartridge wall becomes part of the sensing pathway.
2Ease of operation
If attenuative optical bubble sensors are used, then non-invasive sensing is achieved, but frequent calibration is required and it is difficult to calibrate with multiple liquids
Solution Approach 1:
The patent changes the detection parameter from light intensity attenuation to light refraction angle. Instead of measuring how much light is absorbed (which varies with liquid properties), the system measures the angle at which light refracts when passing from liquid to gas, a parameter that is consistent across different liquid-gas interfaces.
Solution Approach 2:
The system detects changes in the optical path of light rather than relying on absorption characteristics. By monitoring the position and angle of refracted light, the system can distinguish bubbles from liquid without being affected by the specific optical absorption properties of different liquids.
3Device complexity
If refractive index differences are used for detection, then bubbles can be detected in rigid cartridges without complex mechanisms, but the sensor must differentiate between liquid and gas optical properties
Solution Approach 1:
The patent applies a localized measurement approach by detecting refraction at the specific liquid-gas interface within the flow channel. Instead of measuring bulk properties, the system focuses on the local optical behavior at the bubble boundary, where the refractive index difference creates a detectable refraction angle.
Solution Approach 2:
The system measures the refraction angle parameter, which changes dramatically at the liquid-gas interface due to the large refractive index difference. This parameter change provides a clear, unambiguous signal for bubble detection that is independent of the specific liquid type.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable and efficient detection of bubbles in rigid disposable cartridges, ensuring sterility and reducing the need for complex loading mechanisms, thereby improving the accuracy and simplicity of bubble sensing in medical fluid management systems.
Implementation Method 1
the majority of the incident light refracts at a liquid interface between the fluid flow channel and the liquid and travels through the entirety of the fluid flow channel
Implementation Method 2
in the presence of a gas in the fluid flow channel of the wettable component, the majority of the incident light reflects at a gas interface between the fluid flow channel, or the liquid in the fluid flow channel, and the gas
Implementation Method 3
the at least one optical receiver is disposed such that it intersects at least one of: the majority of incident light refracted; and, the majority of incident light reflected
Data Source
AI summary
An optical sensor includes: a sensor portion, having a transmitter and at least one receiver, configured to couple to a wettable component having a fluid flow channel, wherein the transmitter is disposed to emit a light that travels from the sensor portion to the wettable component where a majority of the light is directed towards the fluid flow channel at an angle between a first critical angle and a second critical angle; wherein with liquid filling the fluid flow channel, the majority of the light refracts at a liquid interface and travels through the entirety of the fluid flow channel; wherein with gas in the fluid flow channel, the majority of the light reflects at a gas interface and does not travel through the entirety of the fluid flow channel; wherein the amount of the light refracted and/or reflected and received by the at least one receiver, is used to determine if there is liquid or gas in the fluid flow channel.