Inkjet Printed Heating Elements on Textile Substrate for Functionalized Gloves

This paper focuses on the implementation of a thin-film heating structure dedicated to a human hand form using the inkjet printing technology, on a textile substrate for the application area of flexible wearable technologies. The involved methods are diversified into preliminary investigations of conductive heating elements with basic meander structures that are varied in their geometric parameters, as well as the manufacturing process and subsequent development and validation of the heating structure dedicated to a hand form. To characterize the heat development, the applied voltage is increased incrementally while recording the current flow. Simultaneously, a thermal imaging camera is used to monitor the temperature development over the heated surface. The printed structures are analyzed using an optical microscope. The heating elements are designed separately using individual finger structures in a meander pattern with a line width of 1 mm and three printed layers. The heating performance of the finger structures on the textile substrate demonstrated comparable stable and homogeneous heating results to those that are already well-established on polymeric substrates. The structures associated with fingers of the hand palm are additionally validated by a long-term test over 72 h at ≈60 °C, revealing a great stability with negligible fluctuations. Furthermore, the heating of a thermal hand model at room temperature is triggered to an elevated average core body temperature of 37 °C, demonstrating the application in e.g., the professional medical sector as well as leisure outdoor activities.