Electrovibration In Ungrounded MacBook Pros

My 2011 15” MacBook Pro

A few weeks ago, I noticed that the aluminum enclosure of my unibody Macbook Pro had a strange texture when I brushed my hand across the surface. After some tinkering, I noticed that this only happened when the device was being used while charging and that it only happened when using my shorter, 2-prong, power cable—leading me to believe there was some sort of current leakage happening.

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Impairments to Tactile Perception

Managing diabetes can be extremely difficult, but the risks otherwise can be severe
Managing diabetes can be extremely difficult, but the disease may otherwise cause nerve damage.

Skin sensitivity can be impaired by many different diseases and disorders. Although skin injuries (burns, incisions, etc.) and nerve lesions (from injury or restricted blood circulation) are the most commonly experienced causes of decreased sensitivity, several metabolic, toxic, and immunologic factors can influence haptic perception.
One of the most common complications of diabetes, known as diabetic neuropathy, results in damage to the nerves of the body that cause numbness, tingling, and pain. Diabetes can also slow the healing of cuts and cause rashes that alter the sensitivity of an area of skin. Continue reading “Impairments to Tactile Perception”

How Humans Explore Objects via Touch

A person holding a strawberry in their hand.

People rapidly and accurately identify 3-dimensional objects using only their sense of touch [1]. This process occurs through a sequence of exploratory procedures that underlie the cognitive strategies used to conclusively identify an object entirely through its haptic features. The following four procedures are the most common methods for tactile exploration [2]. Continue reading “How Humans Explore Objects via Touch”

Why Moment Doesn’t Need an LCD Screen

Moment Prototype Photo
Moment allows you to develop an intuitive sense of time, direction, and much more

In the past few years, the growth of wearable technology has exploded. In the process, two types of devices have emerged: smartwatches and health trackers. Smartwatches offer users smartphone notifications pushed to their wrists, where they can interact with the information in a familiar way—through capacitative touch screens while fitness trackers take in a variety of data using sensors, from heart rate to accelerometer measurements, to give users a better understanding of their physical activity.

In designing Moment, we went in the opposite direction and questioned the assumptions made by other wearable devices. Wearable technology should communicate with users by taking advantage of what the body does best. Continue reading “Why Moment Doesn’t Need an LCD Screen”

Tactile Illusions: Interesting Ways Our Brains Fail

Waterfall by MC Escher
If you haven’t seen enough optical illusions, check out some MC Escher artwork.

If we’re honest about shortcomings in human physiology, optical illusions would be labelled “Brain Failures.”

– Neil DeGrasse Tyson

When we think about the ways our perception plays tricks on us, optical illusions come to mind first. They’re not the only kind of sensory illusions, though. Tactile illusions also illustrate the fascinating ways that our perception ‘fails’ to reflect reality. In this post, we describe several different types of tactile illusions.

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How It Works: Linear Resonant Actuators

Diagram of a linear resonant actuator.
Diagram of the construction of a linear resonant actuator.

A linear resonant actuator is a vibration motor that produces an oscillating force across a single axis. Unlike a DC eccentric rotating mass (ERM) motor, a linear resonant actuator relies on an AC voltage to drive a voice coil pressed against a moving mass connected to a spring. When the voice coil is driven at the resonant frequency of the spring, the entire actuator vibrates with a perceptible force. Although the frequency and amplitude of a linear resonant actuator may be adjusted by changing the AC input, the actuator must be driven at its resonant frequency to generate a meaningful amount of force for a large current.

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Electrovibration and Touchscreens: Creating Virtual Textures

Graph of Perceived Friction by Voltage
A higher voltage results in a higher perceived friction.

In 1950, Edward Mallinckrodt, a researcher at Washington University in St. Louis, accidentally discovered the phenomenon of electrovibration (also known as electrostatic vibration). He noticed that a brass electric light socket had a different texture when a light was burning than it did when the light was turned off. Along with a team of researchers, he began exploring the phenomenon in more detail by running experiments using an aluminum plate with insulating varnish. They wrote:

If the dry skin of one’s finger is moved gently over a smooth metal surface covered with a thin insulating layer, and the metal is connected to the ungrounded side of an 110-v power line, the surface has a characteristic feeling that disappears when the alternating voltage is disconnected.

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Haptics and Emotion: How Touch Communicates Feelings

When we think about the content of a conversation, it’s easy to focus on just the verbal information exchanged through spoken words; however, there are many other factors that color our interpretation of conversations and, in turn, the information they communicate. One such consideration is the context provided by prosody—the intonation, stress, tempo, rhythm, and pauses in a person’s speech, all of which lend their voice a unique texture. The brain also employs detailed mappings that link different kinds of facial expressions and gestures with the emotions and nuances that they convey. In fact, up to 65% of the raw information in a conversation is exchanged nonverbally [1]. As we continue to investigate human communication, we uncover a highly complex, multi-modal system that comprises many of our senses—including our sense of touch.

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A Brief History of Haptic Feedback in Video Games

Picture of Fonz arcade cabinet
The original Fonz arcade cabinet

Currently, almost every modern video game console includes some form of vibrotactile feedback, but this was not always the case. As an increasing number of video games were made for computers and at-home entertainment systems, arcade game manufacturers sought ways to make their cabinet games more immersive. Though arcade controls were typically customized to each individual game, the increasing availability of video games outside of arcades placed pressure on companies to provide arcade visitors with experiences more uniquely tailored to branded game cabinets. In 1976, Sega’s game Moto-Cross (rebranded as Fonz) was the first to feature vibrotactile feedback, allowing each player to feel the rumble of their motorcycle as it crashed with another player’s bike on the screen. The control scheme was a success.

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