Capacitive-Sensing Flow Cassettes for Small-Volume Processing

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Solution Overview

Problem

Existing cell washing systems require large volumes of wash media due to their internal volume, making it difficult to process small volumes of cellular suspensions efficiently.

Innovation Solution

A disposable fluid circuit with a reusable processing machine that includes a separation chamber, flow control cassette, and capacitive sensors, along with a controller to operate the system according to a protocol, allowing precise control and minimization of internal volume.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a disposable fluid circuit with large internal volume is used, then the system can handle various cell processing tasks, but it requires large volumes of wash media which is inefficient for small volume processing

Engineering Contradiction:

Improvevolume of wash mediaVSAvoidcapability to process various cell volumes

Core Design Contradiction:

Quantity of substanceVSAdaptability or versatility

Solution Approach 1:

The fluid circuit is divided into modular components including a flow control cassette with selectable junctions and a separation chamber. This segmentation allows the system to be configured for different processing volumes by selectively activating different flow paths, enabling efficient small volume processing while maintaining the capability to handle larger volumes when needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system incorporates dynamically controllable flow paths through selectable junctions that can be opened or closed based on the processing requirements. This dynamic configuration allows the same fluid circuit to adapt between small volume (e.g., 10 mL) and large volume (e.g., 50-5000 mL) processing modes, optimizing wash media usage for each scenario.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If traditional fluid circuits are used, then the system structure is simple, but it lacks precision in fluid control and interface detection

Engineering Contradiction:

Improvefluid interface detection precisionVSAvoidsystem structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Traditional mechanical level sensors or visual inspection methods are replaced with capacitive sensing technology. The capacitive sensor detects fluid interfaces (e.g., air-liquid boundaries) by measuring changes in capacitance, providing precise and automated detection without complex mechanical moving parts, thus enhancing measurement precision while keeping the overall structure relatively simple.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

A flow control cassette serves as an intermediary component between the simple fluid circuit and the control system. It integrates selectable junctions and capacitive sensors, translating simple fluid flow into controllable, measurable signals that enable precise fluid management without requiring complex direct integration of sensors and control mechanisms throughout the entire system.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If manual fluid control is used, then the system is easy to operate, but it cannot provide precise control for small volume processing

Engineering Contradiction:

Improvefluid control precisionVSAvoidsystem operation simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

Capacitive sensors provide real-time feedback on fluid levels and interface positions within the circuit. This feedback is processed by a controller that automatically adjusts flow control elements to maintain precise fluid management. The closed-loop control system achieves high precision in small volume processing while remaining easy to operate, as the system self-regulates based on sensor input without requiring manual intervention.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system incorporates self-regulating flow control through the combination of selectable junctions and capacitive sensing. The circuit automatically detects when fluid reaches certain levels or when interfaces need to be positioned, and adjusts flow paths accordingly without operator intervention. This self-service capability provides precise fluid control for small volumes while maintaining operational simplicity.

Inventive Principle:

Principle #25Self-service

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 efficient processing of small volumes of cellular suspensions by reducing the need for large volumes of wash media and enhancing precision in fluid control.

Implementation Method 1

at least one capacitive sensor disposed on the wall of the at least one interface sensor chamber

Methodology Applied

Scientific EffectCapacitive sensing: Capacitance

Data Source

PatentUS12415165B2Small volume processing systems and methods with capacitive sensing

Publication Date: 2025.09.16 FENWAL INC

AI summary

A fluid processing system may include a flow control cassette comprising at least one interface sensor chamber in fluid communication with at least one of a plurality of separate channels, the at least one interface sensor chamber defined at least in part by a wall, and at least one capacitive sensor disposed on the wall of the at least one interface sensor chamber. The fluid processing system may include, in the alternative or in addition, at least one syringe comprising a wall defining a barrel having a first end and a second end, the barrel having a bore with or without a piston or plunger disposed therein, and at least one capacitive sensor disposed on an outer surface of the wall of the syringe.