The TCR characterizations of the metal strips on a COC substrate did not yield trustworthy TCR values at the first cycle. The first temperature cycle can be seen as a kind of thermal annealing, and therefore gives an hysteresis in the graphs, as can be seen in Figure A2 in Appendix C.1. After this first cycle, the values more or less show the linear behavior. The resulting TCR of this linear part is in agreement with the TCR ranges of Belser and Hicklin [64] and is given in Table 4. Belser and Hicklin used for their experiments substrates with coefficients of linear thermal expansion lower than 1.2 × 10−5 °C−1 [64]. The coefficient of linear thermal expansion for Au and Pt are 1.42 × 10−5 K−1 and 0.88 × 10−5 K−1, respectively [68]. COC of the grade TOPAS 6017 has a coefficient of linear thermal expansion of 6.0 × 10−5 K−1 [42]. This mismatch in coefficients of linear thermal expansion can give strain in the metal layers. Both Au [69,70,71] and Pt [72,73,74] are used as strain-sensitive gauges, and thus are sensitive to strain-induced geometry changes due to thermal expansion.