We propose a microfabrication technology for a flexible temperature sensor with a 100x100 mu m(2) sensing area and a probe length of 7 cm. We use a biocompatible new high temperature-resistant polyimide (U-Vamish-S, Ube, Dosseldorf, Germany) to embed a thin film platinum resistor as sensing element. The sensor is operational from 0 degrees C up to 400 degrees C with an accuracy of +/- 1 degrees C at high temperatures and has a time constant of 0.05 seconds. This sensor was designed for temperature characterisation of hot steam injected for thermo-ablation of tumors via a micro-needle.