Force-sensing resistor is a substance whose resistance changes when a force, pressure or mechanical pressure is applied. They are also known as [the] “Force-sensitive resistors] And are sometimes referred to by initialism  “FSR]”
Force-sensing resistors have a conductive polymer that changes resistance in a predictable manner after the use of force on its surface.  They are usually supplied as a polymer sheet or ink that can be applied by screen printing. Sensing film consists of both electrical lyrical and suspended non-operational particles in the matrix. Particles are sub-micrometer sizes, and are designed to reduce temperature dependence, improve mechanical properties and increase surface durability. Sensing causes particles to apply a force to the surface of the film to touch the conductor electrode, changing the resistance of the film. As with all resistive-based sensors, force sensing resistors require a relatively simple interface and can work satisfactorily in moderately hostile environments. Compared to other force sensors, the advantages of FSRs are their size (thickness generally less than 0.5 mm), low cost and good shock resistance. One disadvantage is their low precision: the measurement result may vary 10% and more. Force sensing capacitors provide better sensitivity and long-term stability, but require more complex drive electronics.
Operation Principle of FSRs
The force-sensing resistors have two major operation principles: the intercept and the quantum tunnel. Although both phenomena are actually found together in conductive polymers, one phenomenon dominates the other at the base of particle concentration. Particle concentration is also referred to in literature as filler volume fraction [display style [phi ] phi. Recently, new mechanised explanations have been installed to explain the performance of force-sensing resistors; These are based on the properties of contact resistance [display style R_[C]R_]C] occurring between sensor electrodes and conductive polymers. Particularly force-driven transitions from Sherwin contacts to traditional Holm contacts. Contact resistance, [display style R_[C]R_[C], plays an important role in the current conduction of force-sensing resistors in a two-time manner. First of all, for a given applied tension [display style [sigma ]sigma, or force [display style F]F, a plastic distortion sensor Occurs between electrodes and polymer particles thus reducing contact resistance. Second, uneven polymer surface is flattened when subject to incremental forces, and therefore, more contact paths are created; This causes an increase in the effective area for current conduction [display style A]A. on a macroscale, smooth polymer surface. However, under a scanning electron microscope, the conductive polymer polymer polymer is irregular due to the pile of binder.
there is a comprehensive model not able to predict all non-linearities observed in force sensing resistors. Many events in conductive polymers become very complex so that they can all embrace together; This condition is typical of condensed material systems involved within physics. However, in most cases, the experimental behavior of force sensing resistors can be approximate for atrocious equations controlling the quantum tunnel through either the interception theory or a rectangular potential barrier.
History of force sensitive resistor
In 1972, Franklin Eventoff started developing a series of musical instrument controllers. Five years later (1977), he invented force sensing resistor or force sensitive resistor.
In 1985, Franklin Eventoff founded Interlink Electronics, a company based on its invention, force sensing resistors.
Advantages of force sensitive resistor
- Low cost
- Small size
- Highly sensitive to force
Applications of force sensitive resistor
- Musical instruments: In musical instruments, the force sensitive resistors are used to translate the emotions of a person into musical expressions through his touch.
- Computer input devices: Force sensitive resistors are used to control the force and speed of the cursor movement.
- Industrial applications: Force sensitive resistors are used in brakes, seat occupancy detection, motor speed control and mirror adjustor.
- Robotics fingertips
- Medical applications