Straining for Relief

As I put fingers to keyboard to write this blog, I’ve recently thrown away my second lightning charging cable since purchasing a new smart device late last year. To say that writing a blog about strain relief was kismet before pitching the cable in the waste can, has to be the understatement of 2017. All of which is a near-perfect segue into the importance of strain relief solutions for plastic tubing assemblies.

If it helps, think of strain relief as a boot or jacket one slips over a delicate plastic tube, increasing its life and mitigating leaks.

In the world of in vitro diagnostics, strain relief solutions relieve tubing of stresses and tensions that may cause the tubing to bend, kink or twist — thereby limiting its inner diameter and impeding fluid flow — which could lead to leaking.

Factors to consider when incorporating strain relief solutions into a design include the size and material of the tubing, the mobility requirement for the tubing, the interaction of the strain relief material with the tubing, and the space available inside the instrument. Standard strain relief options might include springs, spiral wrap, heat shrink or formed plastic sleeves. Another option is to thermoform the entire assembly to avoid unwanted compression.

In addition to limiting leaks, the benefits of strain relief solutions include:

  • Enhancing flex-life performance by limiting over-flexing
  • Preventing kinking
  • Mitigating abrasion
  • Promoting positive fluid flow

For design engineers working on next generation diagnostic instruments, incorporating strain relief solutions early into a design may help one to achieve the accuracy, performance and cost parameters of a project.

Diba delivers exceptional fluidic outcomes across an entire system fluid path. Our proven expertise designing and manufacturing precision fluidic handling systems ensures optimized performance, reliability, and superb field serviceability of instruments in laboratories around the world.

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Tubing Material Selection Can Affect Carryover … Big Time

Labs in the United States run seven to ten billion blood tests annually influencing more than 60% of clinical decision making. On any given day, that’s millions of blood samples running through millions of meters of tubing within today’s most technologically advanced diagnostic instruments. With that many chemistry panels being analyzed, there’s bound to be inaccuracies. The key here is to reduce inaccuracies to as close to zero as possible before a test panel is even run, by optimizing flow path management and through superior fluidic solutions. Carryover from one sample to the next is always a risk.

So, what is Carryover?

Carryover is defined as the remnant of a sample left over in the flow path that gets picked up in a subsequent sample. Although there are several system components which can affect carryover – the aspirate/dispense probe and unswept fluid volume readily come to mind – for now we will focus on tubing material selection.

When a fluid traversing the fluid path picks up some volume of a preceding fluid, it becomes diluted; it no longer has the same concentration. This can be problematic when multiple critical fluids travel through one fluid path.  Changes in concentration can lead to false readings and misdiagnosis.

Materials with low surface energy such as PTFE, FEP, PEEK, ETFE, and MFA are used for the flow path in an effort to reduce fluid carryover. If a fluid flowing through a piece of tubing has a higher surface energy than the tubing itself, it will usually stay bound to itself, and not bind to the inner-diameter surface of the tubing.  This reduces the likelihood of carryover, as the next fluid moving down the flow path may not encounter any of the previous fluid to pick up.

Newly marketed diagnostic instruments and their assays are becoming more and more sensitive. This greater sensitivity is likely to require more stringent control of carryover from one sample being tested to the next. Thus, the tubing choices made for today’s more sophisticated diagnostic analyzers are even more critical than in the past.

Forewarned is forearmed. So, understanding what’s involved with carryover at the onset of a design goes a long way to offering a design solution to help OEMs to solve this problem in today’s more sensitive, precise and faster diagnostic instruments.

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Thermoformed Tubing Simplifies Routing Within IVD Instruments

Today’s diagnostic machines are doing more and becoming increasingly more sophisticated with each instrument release. Due to ongoing technological advances, the range and complexity of diagnostic tests continues to increase. This has made lab tests more sensitive, precise and fast.

However, these better diagnostic instruments aren’t without a downside. From a design perspective, this downside comes in the form of more hardware and components packed into smaller spaces inside the instruments. This makes the fluid pathways difficult to plumb and a challenge to service.

Tight spaces in analytical instruments can put regular tubing at risk of damage from being pinched or worn prematurely by moving parts. But with a thermoformed tubing solution, solving complex routing in tough-to-reach places inside a diagnostic instrument becomes much simpler.

Thermoforming provides shape to the tubing to keep it intact and out of harm’s way inside the instrument. Thermoforming can prevent kinks and deformations caused by moving gantries, closing doors, and other moving parts. Additionally, thermoforming helps design engineers save space within an instrument as the improved bend radius allows for tighter transitions between fluidic connections and economizes volumetric requirements. Further, thermoformed bends assist speed of assembly and minimize damage during installation while maintaining the circular cross-section of the tube throughout the bend.

More Art Than Science

Thermoformed tubing assemblies from Diba’s engineering team can be custom-designed with precision bends and coils that fit neatly inside an instrument, preventing kinking and improper installation for problem-free processing. These assemblies can be custom-labeled and packaged and come in a variety of tubing materials (FEP, PTFE, PFA, ETFE, PVC, LDPE, PVDF, TPU, and PEEK) to speed instrument build cycle and field service times.

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