Optical Tweezers as a microrheological probe of soft surfaces

Microfluidics aims to reduce reaction vessels and connecting conduits to 'lab-on-a-chip' dimensions. However, flow in these channels is not the same as in larger pipes: near solid walls, the friction on a micron-sized particle is enhanced and this affects the transport and energy requirements of microflow. These micro-fluidic walls need not be solid, but can also be soft: the biological cell (the very epitome of a microfluidic device) has soft walls whose flexibility changes. Here we apply the CI's recently developed optical technique to investigate friction near fluid-fluid interfaces and soft surfaces; characterise the method on a new tunable soft surface; and develop this into a tool for measuring mechanical properties of membranes.