The Science Behind Touchscreens: Why Sausages Work When Gloves Don't

Have you ever wondered why your smartphone responds to your bare fingers but not when you're wearing gloves? The answer lies in the fascinating science of touchscreens. Let's delve into the technology that powers our digital interactions.

A Brief History of Touchscreen Technology

The first touchscreen was invented in 1965 with the intention of helping British air traffic controllers efficiently update flight plans. While innovative, the technology was too cumbersome and expensive for widespread adoption. Over the next several decades, engineers refined the technology, leading to the rise of resistive touchscreens. However, the release of the first iPhone in 2007 marked a turning point, popularizing capacitive touchscreens, a technology based on the same principle as the original touchscreen.

Resistive vs. Capacitive Touchscreens: Understanding the Difference

Today, capacitive and resistive touchscreens are the two most prevalent types. Both rely on external input to complete electrical circuits, but they function in fundamentally different ways.

Resistive Touchscreens

Resistive touchscreens are composed of two layers:

• A clear, flexible top layer (typically plastic)
• A rigid bottom layer (like glass)

Both layers are coated with a conductive substance and separated by a thin gap. When you apply pressure to the screen, the layers connect, completing the electrical circuit. This change in voltage is then interpreted by the device's software.

Advantages of Resistive Touchscreens:

• Generally inexpensive to manufacture
• Durable and resistant to damage

Disadvantages of Resistive Touchscreens:

• Can be less responsive than capacitive screens
• Require more pressure to register a touch

Capacitive Touchscreens

Capacitive touchscreens, commonly found in smartphones, typically consist of:

• A protective, insulating glass exterior
• An LCD screen for displaying images
• Several sheets between the glass and the LCD screen

One of these sheets is lined with rows of a transparent, conductive material carrying an alternating electric current. These rows are separated from columns by a thin insulating layer, forming a grid. The intersection points of these lines are called nodes.

The phone's battery sends electrons along the first layer of lines, causing them to accumulate at each node, creating a small electric field. These nodes act as capacitors, storing charge. When you touch the screen, your finger interacts with the electric field, inducing a weak electric current that flows back into the phone, altering the charge at the affected nodes. Voltage measurements along the second layer of lines then pinpoint the location of the touch.

Advantages of Capacitive Touchscreens:

• More responsive and sensitive to touch
• Offer multi-touch capabilities
• Brighter and clearer display

Disadvantages of Capacitive Touchscreens:

• More expensive to manufacture
• Can be less durable than resistive screens

Why Sausages Work: The Role of Conductivity

So, why could South Koreans use sausages to operate their smartphones during a cold winter? The answer lies in conductivity. Your body is a good conductor of electricity due to its high water content and the presence of ions (charged atoms or molecules). When you touch a capacitive touchscreen, your finger acts as a third electrical line, completing the circuit.

Gloves, on the other hand, are typically made of insulating materials, preventing the flow of electricity. This is why they don't work on touchscreens. Sausages, and other conductive objects like banana peels, can mimic the electrical properties of your finger, allowing them to activate the screen.

The Future of Touchscreen Technology

Touchscreen technology continues to evolve, with advancements in areas like foldable displays, haptic feedback, and improved responsiveness. As our reliance on touch-based interfaces grows, expect even more innovative developments in the years to come.