Shock absorbing protective cover for mobile phones and tablets is itself a great area of research and appeal apart from the extensive digital machine lying underneath. There were times when one feet drop of a phone produced enough physical damage to render it useless. Since then protective covers come in different materials and textures, to be lightweight as well as attractive. But why not try a gadget enclosed with a magnetorheological fluid as a protective casing?
Magnetorheological fluid is a smart fluid which acts like a normal fluid at ground state, but becomes a quasi-solid under the influence of magnetic field. It consists of micro-sized magnetic iron particles suspended in a career fluid, usually a type of oil. At normal conditions, the object behaves just like any normal viscous liquid. But when a magnetic field is applied, the ferromagnetic particles align themselves according to the direction of magnetic field, and hinder the flowability of the liquid. Thereby the viscosity of the fluid increases to such an extent as to become a viscoelastic solid. Such a state of a viscous liquid suspended with aligned micro solid particles effectively absorbs shock vibrations; hence they are used in dampers, brakes, clutches and journal bearings.
The main objective of magnetorheological fluid is to maintain it as a fluid and to turn on the magnetic field at the exact time required. This is achieved with a precise sensing and control system, to initiate magnetisation at the exact moment when a brake or clutch pedal is pressed. Now let us try to take it a step further, i.e. to activate the magnetic field autonomously without human interference. That would need a sensing system to sense the conditions when damping is required, and activate the magnetic circuit instantaneously.
For example, let us consider a mobile phone covered with a thin layer of magnetorheological fluid at its rear and side surfaces. At normal usage conditions, it is supposed to behave as viscous fluid, analogous to a silica case. When accidentally the device is dropped, this sudden increase in acceleration due to free fall is to be sensed by a sensor, and turn on a trigger to an electromagnet. The electromagnet then becomes magnetised, inducing the ferromagnetic iron particles inside the fluid to align along its magnetic orientation. When all this happens within few milliseconds, the damper will get activated and absorb the shock when the phone hits the ground.
Magnetorheological fluids have the potential to offer more advanced properties and applications, such as in helmets and alternative for Kevlar. With more research and high volume production, such life-saving smart fluids may become a common entity one day.