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Llewellyn Sims Johns

StretchSense Smart Garment Preliminary Washability Findings

Introduction

StretchSense Smart Garments are designed to capture motion data from the human body to enable new motion capture applications in sports, gaming, and healthcare. Our Smart Garments are a prototyping platform for other businesses to develop new user experiences based on human movement. Just like any other item of clothing, it is important that our Smart Garments survive the washing process without performance degradation. StretchSense, therefore, has begun work to ensure our garments can be washed for end consumers when produced at volume.

 

Hypothesis

We hypothesized the following as potential modes of failure during the washability testing:

  • Water collecting in small cavities. This could cause corrosion of the connectors, or cause low- or high-resistance short circuits between connector pins.
  • Physical damage caused by agitation, such as any point of the cable assembly including cable terminations.
  • Fabric or sensor damage due to wash temperature or spin severity.

 

Industry Standards for Washability

Currently, there is no industry standard for washability testing when it comes to smart clothing. StretchSense, therefore, has set a benchmark of 150 wash cycles in our next washability project – based on a well-used activewear garment being washed three times a week for a period of one year.  The results of this test will be published in a later report, as we aim to provide customers a washability guarantee.

 

Experimental Method for Preliminary Washability Testing

Three Smart Garments were used for this stage of testing:

  1. One Smart Shirt using the Generation 1  enclosure connection: a 2×10 pin header with short soldered extension cables and male cable terminations to mate with the standard female 2 pin connector of the sensor cable assembly.
  2. One Smart Elbow Sleeve using the Generation 1 enclosure connection.
  3. One Smart Shirt using the Generation 2 enclosure connection: a modified circuit enclosure with recesses for retaining the standard female 2 pin connector of the sensor cable assembly directly to enable connection to the electronics without requiring additional connection points.

All garments had their electronics, battery and enclosure lid removed before washing.

The garments were washed in a Primus RX80 Washer using a gentle cold wash cycle without detergent. The wash program used consists of the following stages:

  1. Wash for 6 minutes, then drain;
  2. Rinse for 2 minutes, then drain;
  3. Rinse for 2 minutes, then drain;
  4. Rinse for 3 minutes, then spin at 250 RPM for 2.5 minutes;
  5. Tumble for 0.5 minutes.

Initially, garments were washed once and then hung to air-dry overnight at room temperature before being tested.

After the first 5 washes, the test procedure was modified to accelerate testing. The modified process consisted of:

  1. Garments being washed inside a standard wash-bag, using the same gentle cold wash cycle as above, with the addition of half a cup of regular consumer-grade washing powder;
  2. Garments being washed five times, after which garments are removed, checked for visible issues, and then tested while still wet;
  3. Garments being hung out to dry overnight and tested the next morning before repeating the process again from Step 1 of the modified process.

 

Experimental Results

As of writing this report, the garments have been washed a total of 12 times and dried overnight three times. The following table details the testing results.

 

  1 Wash 2 Washes 4 Washes 9 Washes 12 Washes
Smart Shirt, Generation 1 connection Pass Pass Pass Pass Fail
Smart Elbow Sleeve, Generation 1 connection Pass Pass Pass Pass Pass
Smart Shirt, Generation 2 connection Pass Pass Pass Pass Pass

 

After 12 washes, the Smart Shirt with the Generation 1 connection had 1 sensor out of 6 break due to physical damage. The point of failure was between the cable and the connector of the sensor where it connected to the extension lead from the enclosure. This connection point was identified as having a high risk of failure due to not being mechanically supported nor having additional strain relief. For these reasons, it was eliminated in the Generation 2 enclosure and the connection between the cable and connector has been strain relieved to eliminate mechanical fatigue.

 

Conclusion and Discussion

Our preliminary testing results are promising regarding the washability of StretchSense Smart Garments. From our preliminary testing, our Smart Garments with the Generation 2 connection are not at great risk of being damaged by agitation in gentle machine wash or by being immersed in cold water or detergent, and that when air dried are fully functional.

We will continue to wash test our smart garments and continue to improve our design and integration when new failure modes become apparent.

It is too early to offer any guarantees regarding washability, however, based on preliminary experimentation, our draft recommendations for care instructions are:

  • Cold hand wash if possible
  • Cold machine wash on gentle or wool cycle
  • Air dry
  • Do not bleach
  • Do not tumble dry
  • Do not dry clean
  • Do not iron

In the next washability project, StretchSense will be testing our garment range for 150 wash cycles to achieve full washability at volume for consumer applications.

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