Building upon the concept of transillumination, the aim of this study is to develop an idiot-proof cost-effective pocket-sized VAD (FireFly) to improve venepuncture success. A randomized controlled trial (RCT) will be conducted to determine its safety and efficacy. Two candidate prototypes will be modelled using Computer-Aided Design (Inventor®, Autodesk®, California, USA) and fabricated using 3D-printing. Each prototype will be fitted with light-emitting diodes of a specific wavelength (6500Knm, 4500Knm, or 660nm). Compared to existing VADs, FireFly will be significantly smaller and lighter. It will be constructed using nylon-based polyamide and silicone, with flexible circuitry. Flexibility allows it to conform to the patients' limbs. A large transverse viewing window optimizes vein visualization.