Smart clothing computes wearer’s thermal needs

Smart clothing computes wearer’s thermal needs

Technology News |
By Julien Happich

In November last year, the Finnish research center had unveiled one of the potential building blocks for such self-tuning thermally active clothes: microscopic channel networks hot embossed onto large areas of soft and elastic plastic film, through which cold or hot liquid could be pumped.
Integrated into smart clothing, the microfluidic channels are analogous to the cardiovascular system which irrigates different parts of the body (though it is the human metabolism which defines the blood’s distribution at a given time).

Microfluidic channels to be integrated into smart clothing, with a thermoregulator backpack.

Prior research established that humans dissipate approximately 85% of their body’s heat loss through the skin, so the smart irrigated fabric would act as not only a comfort layer but also double up as a thermoregulatory skin.

But before such “personalised air conditioning” smart fabrics can maintain the wearer’s thermal comfort, they need to be able to regulate their temperature appropriately, so as to automatically adjust to external conditions.

This calls for accurate human thermal model calculations, and the research lab has just developed the tools for that, enabling to correlate surrounding temperature and on-body temperature measurement with a person’s thermal sensations.

As described in Riikka Holopainen’s PhD dissertation, “A human thermal model for improved thermal comfort”, the newly developed model takes into account the effect of human thermoregulation and individual human parameters on thermal sensation and comfort, to calculate more realistically the interaction and non-uniform transient heat transfer between the skin surface and the surrounding air and building structures.

Arguably, smart fabrics driven by such a model would require multiple temperature inputs, distributed around the wearer’s body while also taking into account external temperature and the wearer’s activity level (the human body continuously generates heat from about 75W during sleep to 1 000W during hard exercise). The algorithms may be further optimised for a given person’s body mass index.

The model’s calculations aim to determine the needed warming or cooling power so that the thermal sensation of the person wearing the smart clothing remains optimal in varying conditions. Providing the smart fabrics are designed with both heating and cooling capabilities (maybe with a sort of miniature heat exchanger belt or backpack integrating Peltier elements and heated mats), such wearable technology could find applications across different consumer groups, including police officers, firemen, soldiers, outdoor workers, athletes, in-bound patients and small babies.

“Hospital patients have been asked about their most unpleasant experience, and the most common answer is feeling cold – pain comes only second”, explains Principal Scientist Pekka Tuomaala from VTT.

“For example, patients often feel cold after surgery. Body temperature can be individually adjusted, when a smart blanket identifies the person, measures the ambient temperature and adjusts the blanket’s temperature to meet the patient’s actual needs”.

Small-scale lab experiment showing in real-time the
impacts of changes in ambient air temperature on the heating
power of a small electrically heated mat.

Still a small-scale lab experiment, Tuomaala has proven smart clothing control, showing in real-time the impacts of changes in ambient air temperature on the heating power of a small electrically heated mat.

The lab has yet to establish the sort of control signals that would operate such smart fabrics, but it is looking for companies to further develop the technology and bring products to market.


Visit the VTT Technical Research Centre of Finland Ltd at


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