Torsionally Flexible Sealed Drive for Bioreactor Agitation
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Solution Overview
Problem
Existing bioreactors and mixers face challenges in creating a watertight seal for rotary motion transfer from an external motor to an internal impellor without using lubricants, which is complex and costly, especially in disposable, one-time use equipment.
Innovation Solution
A torsionally flexible, sealed drive apparatus using a stepper motor coupled to a drive shaft through a torsionally flexible tube, with one end sealed to a torsionally rigid barrier and the other end to a motor coupling, allowing rotational oscillation of the drive shaft within the tube to impart oscillating rotary motion to the impellor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional rotary seal is used to transfer motion from external motor to internal impellor, then the seal can be water-tight, but the device becomes complex and expensive
Solution Approach 1:
The patent employs a flexible membrane seal that allows rotary motion to pass through while maintaining a water-tight barrier. The membrane is configured to flex with the rotational movement of the drive shaft, eliminating the need for complex mechanical seals or bearings that would compromise sterility or increase cost. This flexible film approach provides both the required sealing reliability and motion transfer capability in a simple, disposable configuration.
Solution Approach 2:
The invention is designed for single-use disposable bioreactors where the entire sealing assembly is discarded after one use. This eliminates the need for expensive, reusable mechanical seals that require maintenance and sterilization. The seal is integrated into the disposable container assembly, providing adequate sealing for the intended short duration without the complexity of permanent sealing mechanisms.
2Reliability
If a complex seal mechanism is used to allow rotary motion, then the seal can be effective, but the manufacturing cost increases
Solution Approach 1:
The flexible membrane seal is manufactured as a simple, integrated component using standard plastic forming techniques suitable for disposable medical devices. The membrane is bonded to the container wall and drive shaft assembly in a single manufacturing step, avoiding the need for complex assembly procedures or expensive precision-machined seal components. This approach dramatically reduces manufacturing cost while maintaining adequate sealing effectiveness for the intended application.
3Ease of operation
If lubricants are used in the seal mechanism, then the rotary motion can be smooth, but the contents of the container may be contaminated
Solution Approach 1:
Since the entire drive assembly including the seal is disposable and single-use, there is no need for lubricants that could contaminate the sterile contents. The flexible membrane seal operates without lubrication, relying on its elastic properties to accommodate rotational motion. After one use, the entire assembly is discarded, eliminating any risk of contamination from lubricant degradation or accumulation over time.
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
This solution provides a simple, robust, and cost-effective means to transfer oscillatory rotary motion across a sterile seal, effectively agitating contents in bioreactors and mixers for extended periods without contamination, suitable for disposable equipment.
Implementation Method 1
a torsionally flexible tube having a first end in sealed cooperation with a substantially torsionally rigid barrier element surrounding said aperture, and a second end in sealed cooperation with said motor coupling, and wherein said drive shaft is partially disposed within said torsionally flexible tube and said second end of the flexible tube is rotatable relative to the first end of the flexible tube about a central axis
Data Source
AI summary
A simple, robust and low-cost torsionally flexible, sealed drive that allows external drives to provide agitation within a container. A torsionally flexible tube is sealed to a torsionally rigid portion of a container. A second end of the tube is sealed to a driven element within the container. The driven element is coupled to a drive- shaft that is partly contained within the tube. Motion of the protruding end of the drive shaft imparts a corresponding motion to the driven element, while maintaining a water-tight seal between container and drive-shaft. One useful motion is a rotary oscillation. A stepper motor may operate via such a drive to impart a rotary oscillation to an impellor in a bioreactor, or mixing container, suitable for agitating a cell culture in a nutrient medium or hydrating a powdered media in water. The drive is suited to use in disposable bioreactors and mixers.