Textile-Based Flexible Coils for Wireless Inductive Power Transmission

Abstract

Wireless inductive power transmission systems can potentially supply wearable devices. Power cables or batteries can be eliminated by implementing a wireless power transfer system, making the wearable devices less obtrusive to users. However, rigid coils can cause discomfort to users in wearable applications. The novel screen-printed flexible coils on textiles reported here are intended to be a low-cost and comfortable solution when integrated into clothing. A constant-width circular-spiral flat coil has been designed to minimize the detrimental effect of the low conductivity of the screen-printed flexible conductors on the efficiency of the wireless power transfer system. The coils are printed on 65/35 polyester/cotton textile with a screen-printed Fabink-UV-IF1 interface layer coating. The interface layer provides a relatively flat and smooth surface to prevent the permeation of the conductive paste into the textile and allows the printing of finer-profile coils. A 5 V 1.2 W DC output has been achieved by a wireless power transfer system using the printed flexible coils with Qi standard circuitry; a DC-DC efficiency of 37% has been measured.

Fabrication Techniques for Manufacturing Flexible Coils on Textiles for Inductive Power Transfer

“…The silver-loaded conductive paste used to print the coil contains polymer binding agents, and therefore when cures it does not possess the conductivity of the base metal. Simulations [14] of the unloaded Q factor have been used to compare different combinations of track width and number of turns, resulting in the choice here of printing a sixturn coil with an external diameter of 138 mm, a track width of 4.5 mm, with a track spacing of 2 mm.…”

“…The measurement process used is as described by Li et al [14], measurements of maximum power delivered to the load P out put and maximum DC-DC efficiency η DC−DC are made at separations of 5, 10, 15 and 20 mm with the coils positioned so that they are aligned on-axis and with their substrates flat and parallel to one another. The results of these measurements are shown in Table VI.…”

Textile-Based Coils for Inductive Wireless Power Transmission

“…Li et al [7] focused on the development of a textile-based induction coil for contactless energy transfer. They printed various coil geometries on a textile substrate using the screen-printing method.…”

Wireless power transfer-based eddy current non-destructive testing using a flexible printed coil array

“…The single Tx array has been used for measurements of tiny gaps between metallic and non-metallic surfaces [8]. Also, a pair of similar Tx and Rx flexible coils have been investigated for WPT efficiency on consumer electronics [17,19], and integrated smart textile and flexible fabric [20,21]. An array of Tx–Rx pairs of FPC, configured as a rosette eddy current array, were investigated for structural health monitoring and boosting the sensitivity of fatigue crack detection [22,23].…”