TWIGS: Textiles With Integrated Gas Sensors

Giovanni Nisato of CSEM/Division Thin Film Optics , expert in thin film optics

Gerhard Tröster of ETHZ/D-ITET/IFE, expert in Wearable Systems

Project Description

While flexible pressure and temperature sensors are relatively easy to realize, gas sensors are more challenging due to their more complex structure involving gas sensitive materials that must have access to the external environment. Particularly for gas sensors targeting smart textile applications, the challenge is significantly greater since the industrial weaving is a very abrasive process. The main target of TWIGS is  to  is design, fabricate and characterize a mechanically robust thin-film capacitive gas sensor platform compatible with industrial weaving processes. The targeted sensor platform is particularly interesting to develop textile integrated sensors arrays with each individual sensor functionalized with a different sensing material to perform complex sensing tasks.

The 1^st generation of low-power humidity and temperature sensors fabricated on Kapton^® sheets are recently woven into textile using a conventional weaving machine, successfully. The gas sensors on plastic foil with encapsulated active area for protection during stripes dicing, weaving, and operation. The fabrication process is simple, and compatible with large scale roll-to-roll fabrication. Basic tests with CAB and PDMS sensing layers showed that woven sensors survive the weaving process without loss of functionality.

3D representation of the 6 x 2.15 mm sensor stripes is shown above. The active area is 1.5 x 1.5 mm and coated with CAB sensing layer. The temperature sensor is formed by the resistance between E₂ and E₃; C₁₂, C₁₃ or their total value can be used as the gas sensing capacitance.

Images of the woven sensors with and without the Teflon capping layer

The sensors were characterized for humidity response with PDMS and CAB sensing layers. The integrated temperature sensors, as shown on the right, have a linear sensitivity of 1.175 Ohm/°C. The transient capacitance behavior of a woven sensor with CAB sensing layer is depicted on the right, and exhibits good correlation with the reference commercial humidity sensor output.

posters from 2011

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