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Embroidered Driven Shields (2025)


For touch sensitive e-textiles, projected capacitive sensors are frequently applied, since they provide high precision in controlled environments. However, they are notoriously prone to environmental noise, such as EM fields from proximate power lines, or movement of large, nearby conducting objects. This affects the sensor signal quality and range, and consequently the accuracy and reliability, e.g., causing accidental activation. A common strategy to mitigate these issues is by shielding the sensor electrodes.

While shielding is often neglected in textile user interfaces, other works employ grounded shielding, which considerably reduces sensitivity since it draws charge from the sensor. In contrast, in this work, we establish more advanced driven shields (a.k.a. active shields) on textiles, which is a state-of-the-art technique in the context of rigid printed circuit boards (PCB) and flex-PCBs and is therefore implemented in many contemporary sensing hardware. 

The presented solution realizes both sensor and shield electrodes by computerized machine embroidery, harnessing the potential of free-form stitching. We use a common PA yarn as upper thread and an enameled wire as a lower (bobbin) thread. Consequently, both sensor and shield electrodes are applied in a single embroidery sequence with sub-millimeter stitch accuracy, on a single piece of fabric and no tedious and error-prone handling is required, like the composition of multiple layers. 

We investigated the effect of different stitch densities and patterns for the shield electrode. To streamline the workflow, we implemented a custom design software for generating those patterns based on parameters like trace distance, size, stitch length, and pattern type. A major learning of our experiments is that the impact of density on the signal quality is overall minor, while adjustments of the pattern layout can compensate for a lower stitch density. In particular, a grid layout yields the best results, which is comforting for textile designs, since less stitch density results in superior flexibility and favorable haptic properties. Refer to the full IEEE Journal on Flexible Electronics article (Open Access) for more details.

Also, check out a related project for a textile touchpad that supports multi-touch.


Credits: TU Wien, University of Applied Sciences Upper Austria

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External:
Official IEEE Publication (Open Access)
Github repository
Artifact-Based Computing & User Research

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