Colorectal surgery is commonly performed for diverse indications, and most commonly for colorectal cancer. The most serious risk of colorectal surgery is 'leaks' from the surgical join. Leaks are a catastrophic complication for patients, including being the major cause of post-operative death. The critical problem with leaks is that there is currently no method to diagnose them *early*, before an irreversible spiral of sepsis and critical illness takes hold. This project brings together an expert team of scientists, surgeons and engineers to develop a breakthrough early warning device for surgical leaks. The device we are proposing has potential to transform the field of colorectal surgery, making operations safer, and reducing the costs of care due to reduced complications. In this Explorer Grant we will build a clinical prototype device and validate it in bench-top and pre-clinical trials, so that it is ready for future clinical trials.