Tech Explained: Haptic Technology

How do haptics add a sense of touch to devices and virtual environments? Find out more in our latest Tech Explained feature.

The word haptic comes from the Greek haptesthai, which means ‘to touch’. Haptic feedback is the use of force, vibration or motion to create a sense of touch. Haptic technology includes everything from the feel of keys on a keyboard, to adding a sense of touch to AR. Although it has been around for a long time, the use of haptic technology is growing rapidly. The production and implementation of haptic sensors and devices is predicted to be a 12.8 billion USD industry by 2022. So, how do haptics work?

There are several different types of haptics used in everyday devices. Perhaps the most common type uses an eccentric rotating mass (ERM) actuator. This is a fancy name for a rotating electric motor with an off-centre mass. As the ERM rotates, a centrifugal force is created, which causes the motor to move. The movement of the motor creates a vibration. ERMs are commonly used in gaming systems. Although they are relatively low cost, the components tend to be large and use a lot of power.

Another way of generating vibration is through a linear resonant actuator (LRA). This is made up of a magnet which is attached to a spring and surrounded by a coil. When electricity is run through the coil, it becomes an electromagnet. The magnet moves back and forth through the electromagnet, which causes vibrations. LRAs are used in some smartphones and games consoles. They use less power than ERMs and have a more rapid response time, however, they are more expensive and less efficient than ERMs and can wear out.

Another type of precision haptic is the piezoelectric actuator. These are made of a ceramic material. When an electric charge is applied, they expand and contract, generating motion and force. The vibrations of the piezoelectric actuators can be controlled by changing the frequency and amplitude of the voltage. This makes them more precise than ERMs and LRAs. Piezoelectric actuators are used in some devices, like the Kindle Voyage, but are costly and fragile. They also use a lot of power because they require a higher voltage than ERMs or LRAs.

More recently, an accelerated ram has been developed to give both a soft tap and a hard tap. The accelerated ram contains a tiny hammer that is suspended in the air by a magnetic array. A soft tap, similar to a pulse, is created when the hammer is driven into the magnetic array. When the hammer is driven in the opposite direction of the magnetic array, it strikes a solid surface, giving a hard tap. The ram uses less power than the LRA and ERM. A range of effects can also be achieved by adjusting the voltage and frequency.

New types of haptics are also being developed to add a sense of touch to AR. One early AR haptic used a stylus with three small motors to give force feedback to the user as they exerting pressure on the stylus. Other systems fit over the user’s entire hand and use actuators to produce force, which is transmitted to the fingers by the exoskeleton. Researchers at Carnegie Mellon University are developing a haptic interface that uses an electromagnet to levitate a handle. The user manipulates the levitated handle to interact with AR environments. Researchers in Germany have developed a wearable haptic device that provides a low voltage directly to the arm muscles. This allows AR users to interact with virtual objects.

In addition to gaming and AR, graphical user interfaces could also benefit from haptics. In the future, haptics could allow users to feel graphic buttons or make on-screen buttons behave as if they were real buttons. There are many other practical uses for haptics. For example, medical students can use haptic feedback to practise delicate surgical techniques; or soldiers can use them to practice defusing bombs. At Springwise, we have also seen haptics in uses as diverse as art and to aid the visually impaired.