Fabrication and characterization of aluminum thin film heaters and temperature sensors on a photopolymer for lab-on-chip systems

Polymers offer many advantageous physical properties as structural materials for MEMS and microfluidics. Additionally, polymers support rapid and inexpensive fabrication methods. Patterning metals on polymer microstructures is, however, much more challenging than doing so on conventional substrates such as silicon or glass. As a result, metal layers within polymeric devices are typically fabricated on non-polymeric substrates, and the polymer layers are then fabricated on top, which greatly constrains the variety of structures that can be built. A wider range of devices could be fabricated if there was a reliable method for producing and patterning stable metal films on a photo-polymer. Lab-on-chip (LOC) systems in particular would benefit from low-cost, corrosion-resistant, thermally stable metal films embedded in polymer structures. To date, however, there have been no demonstrations that combine all of these characteristics. We present here a method for patterning a film of aluminum on the photopolymer KMPR and treating the film to stabilize its resistivity. We demonstrate the production and stability of the films and demonstrate that they are suitable for use as heaters and/or temperature sensors at temperatures up to 165 °C – well beyond the required temperatures for mainstay LOC functions such as the polymerase chain reaction (PCR).

► Low-cost, thermally stable metal films were patterned on a photo-polymer.
► Presented a method for treating aluminum film on KMPR to stabilize resistivity.
► We demonstrate the film's suitability as heaters/sensors for LOC applications.
► Exceptional adhesion shown between sputtered aluminum and KMPR.
► High stability and linearity of resistivity from 22 to 165 °C for 6 h is achieved.