Disposable and flexible sensors are needed in biomedical and healthcare applications because of hygiene requirements. At the same time, they should provide an affordable solution for point-of-care (POC) testing and large-scale deployment. In this view, herein we report flexible polyimide-based disposable sensor patch for the detection of a-amylase in blood serum. The concentration of a-amylase in blood serum is a potential indicator of health issues such as pancreatitis and pancreatic cancer and an affordable solution to detect its concentration could benefit many. Here, the detection is based on thermal Marangoni circulation inside a microfluidic droplet of starch-FeSO4 salt solution, which detects the a-amylase concentration upon addition of blood serum. It was observed that the temperature difference between the droplet substrate and ambient sets a thermal Marangoni and natural convections motion inside the droplet. The performance of the microdroplet-based sensor was best at temperature difference ( 18-20°C). The sensor is capable of detecting 20-110 units/liter concentration of α-amylase with 80% change in the electrical resistance across the microdroplet (at 40°C substrate temperature), and with a sensitivity of 0.88% (units/liter)-1. The response of the sensor was also compared with pathological laboratory results and both were found to be in agreement. The presented sensor has the potential to be used as a POC device for detecting α-amylase in real-time.