Method for designing and tuning and system for measuring a refractive index of a magnetic fluid

A method for forming a magnetic fluid layer with a tunable refractive index, wherein an external variable magnetic field is optionally applied, the method comprising:

• providing a magnetic fluid, which comprises a fluid base and a magnetic ingredient;
• injecting the magnetic fluid into a substrate cell to have the magnetic fluid layer;
• and
• tuning the refractive index of the magnetic fluid layer under considering at least one of a plurality of parameters consisting of:
• a concentration of magnetic particles of the magnetic ingredient;
• an externally applied magnetic field;
• a magnetic field direction;
• a strength of the applied magnetic field associating with a thickness of the magnetic fluid layer;
• a strength of the applied magnetic field associating with a temperature;
• and
• a strength of the applied magnetic field associating with a sweep rate of the magnetic field.

A method for measuring a refractive index of a magnetic fluid layer under an environment with a condition, wherein the magnetic fluid layer has a magnetic ingredient and is injected in a cell of a substrate, the method comprising:

• putting a prism on the magnetic fluid layer, wherein a side surface against a right angle of the prism contacts with the magnetic fluid layer, and the prism has a prism refractive index np;
• applying an incident light onto the magnetic fluid layer through the prism with an incident angle θi with respect to a normal direction;
• measuring an intensity of the reflected light to determine whether or not an critical angle for total reflection by the magnetic fluid layer is achieved under the corresponding incident angle θi=θit;
• and
• computing the refractive index of the magnetic fluid layer according to a formula of
• 3 n MF = 1 2 ⁢ ( 2 ⁢ ⁢ n p 2 - 2 ⁢ ⁢ sin 2 ⁢ ⁢ θ it - 2 ⁢ sin ⁢ ⁢ θ i ⁢ ⁢ t ) ,
• where nMF is a quantity of the refractive index of the magnetic fluid layer.

A system to measure a refractive index of a magnetic fluid layer, wherein the refractive index is tunable, the system comprising:

• a substrate to hold the magnetic fluid layer, wherein the magnetic fluid layer has a magnetic ingredient in a fluid base;
• and
• a measuring subsystem to measure the refractive index of the magnetic fluid layer, wherein the measuring subsystem allows the refractive index to be tuned under at least one of a plurality of measuring conditions consisting of:
• a concentration of magnetic particles of the magnetic ingredient;
• an externally applied magnetic field;
• a magnetic field direction;
• a strength of the applied magnetic field associating with a thickness of the magnetic fluid layer;
• a strength of the applied magnetic field associating with a temperature;
• and
• a strength of the applied magnetic field associating with a sweep rate of the magnetic field.