Smart bra patent is too obvious to provide legal support

These days I rarely venture into the world of patents but this sports bra case has brought me out of patent retirement. The IPEC recently considered whether a bra that tracks biosignals via side-positioned sensors was a genuine leap forward in wearable tech or just an obvious progression.

Prevayl Innovations Ltd v Whoop Inc [2025] EWHC 399 (IPEC) concluded that the patent was invalid due to a lack of inventive step. While the invention might be supportive in a literal sense, the supportung patent failed to provide the necessary legal uplift.

The fashionable side of biosensors

Prevayl’s patent (GB 2 589 947) covered a bra with biosignal sensors located in the side of the bra rather than more conventional placements like the chest or between the shoulder blades. The goal was to enable better comfort and less visual bulk, especially for the style-conscious athlete. Whoop, a company that offers wearable fitness tech, was accused of infringing this patent with its own smart sports bra and sensor module (the Whoop 4.0).

The court accepted that Whoop's products did fall within the patent claims. However, the case turned on whether the patent was valid, in other words whether the patent should have been granted in the first place.

A perfect fit, or just too obvious?

The key question was whether Prevayl’s claimed design, a sensor assembly entirely in the side portion of the bra, not in the underband, was an inventive step beyond existing prior art. Whoop cited two pieces of earlier tech: a US patent application (US 845) and a PCT application (PCT 853).

His Honour Judge Hacon found that both pieces of prior art disclosed the possibility of placing sensors in side regions, and that it would have been obvious to do so in order to avoid the discomfort and unsightliness of other locations. While Prevayl argued that placing sensors outside the underband wasn’t standard practice, the court concluded that designers had all the necessary knowledge to make the shift. Comfort and aesthetics, they concluded, are hardly revolutionary.

The judge summarised that the skilled team — a combination of garment designers and biosensor experts — would have found the claimed invention an obvious option. In other words, it wasn’t a “hold the front page” moment for the world of wearable tech.

When sensors meet supply chains

Despite the invalidity finding, the court still considered infringement, just in case. Whoop accepted that its sports bra infringed the patent, but contested whether its separate sensor module (the Whoop 4.0) also constituted indirect infringement under s.60(2) of the Patents Act 1977.

The court disagreed with Whoop’s view that the module wasn’t essential. It held that the measuring apparatus, including the sensors, was central to the invention and not a “completely subordinate” element. The supply of the Whoop 4.0, intended for use in the side-pocket of the Whoop Bra, amounted to infringement — or at least, it would have done had the patent survived.

What does this mean?

• Designers and engineers beware: Even if your idea looks stylish and is practical, it may not clear the inventive step hurdle if it’s merely an obvious combination of known components. The fact that something hasn’t been done before isn’t enough, you need a compelling technical reason why it wouldn’t have been done previously.

• Patents in fashion tech are tricky: This case illustrates the challenge of securing strong IP protection for wearable tech especially in garments where comfort and aesthetics drive design choices.

• Indirect infringement still matters: Even with modular tech, separate components can still be caught by UK patent law. Provided they relate to essential elements and are supplied with the intent they’ll be used in a patented combination.