The possibility of using photo-stimulation to perform flow control and sensing in microfluidics is very appealing as light can be applied in a non-invasive and highly precise manner. In the field of stimuli-responsive polymers, hydrogels offer a simple and effective method to fabricate three-dimensional polymeric networks whose water content can be modulated through external stimulation. By incorporating stimuliresponsive units into the gel structure, hydrogels can be actuated by external stimuli such as light, temperature and pH, among others. One of the most popular ways to achieve photo-control is through the use of photo-responsive molecules, such as spiropyrans. This thesis focuses on presenting the synthesis, characterisation and potential applications of stimuli-responsive materials based on spiropyrans, in particular as photo-controlled polymeric actuators, and photo-sensitive coatings. Chapter 1 offers a brief overview of the field of stimuli-responsive materials and photo-responsive materials in particular, and Chapter 2 discusses possible applications of such materials in microfluidic devices. Chapter 3 describes the synthesis and characterisation of photo-responsive hydrogels based on Nisopropylacrylamide- co-acrylated spiropyran-co-acrylic acid (p(NIPAAm-co-SP-co- AA)) copolymer, while in chapter 4 this material is used to produce a millimetresized bipedal hydrogel walker. When subject to light cycles, the bipedal gel produces a walking motion by taking a series of steps in a given direction. Chapter 5 focuses on spiropyran polymeric brushes as coatings in micro-capillaries and confirms their potential for metal ion binding, sensing and release. Chapters 6 focuses on the synthesis and surface functionalisation of other spiropyran derivatives and describes future work in the area of photo-responsive materials and hydrogels.