In this blog post, we will learn about the principles of capacitive touch screens, the flow of electricity, and how our bodies act as conductors.
In 2024, the top 10 global brand rankings will include Apple, Microsoft, Amazon, Google, and Samsung Electronics from South Korea. What do these companies have in common? They are all companies that specialize in electrical or electronic products. Now, let’s go back to when you woke up this morning and look back on your day. You get out of bed, take a warm shower, and check your smartphone, which you plugged into the charger the night before. You eat breakfast and take public transportation to work or school. You work on your computer under fluorescent lights, attend meetings, and listen to lectures. Every single step of this process involves technology that uses electricity. Electricity is essential to our lives, and it is also a very important resource that creates added value and enables continuous development and growth for more than half of the companies ranked in the top 10 global brand value rankings.
Let’s take a look at the principles behind electricity, which enriches our lives in so many ways. All matter in the world is made up of atoms. Atoms consist of a nucleus at the center and electrons. Electrons can be divided into two types: those that are bound to the nucleus and those that move freely, called free electrons. The free electrons are the particles that enable electricity to flow. When a potential difference is applied to these atoms, the free electrons around the atoms flow in one direction, causing electricity to flow. Let’s look at an easier example. Imagine that there are marbles rolling around in a box. Let’s think of these marbles as free electrons. On a flat surface, these marbles roll around freely. Now, lift one corner of the box. All the marbles will gather at the opposite corner. If you imagine that the box is a very long tube, the marbles will roll downwards all at once, which is what we see as the flow of electricity.
Depending on the degree to which electricity flows, materials in the world can be divided into conductors, insulators, and semiconductors. The “degree to which electricity flows” can be thought of as the “number of free electrons” mentioned earlier. Conductors are materials that have many free electrons, so even a small potential difference causes electricity to flow easily. Metals, which we commonly use in electrical wires, are good examples of conductors. Insulators have almost no free electrons, so even when a potential difference is applied, electric current does not flow easily. Rubber and plastic are examples of insulators. Semiconductors are materials that are normally insulators but allow electric current to flow when certain conditions are met. They are mainly made by combining various materials and are used in computer chips and various electronic devices.
So, is our body a conductor or a non-conductor? You may have heard of cases where people have been electrocuted or struck by lightning. The human body is also a conductor, so when a potential difference is applied from outside, electricity flows through the body, causing accidents. Until now, people have only thought about the dangers of electricity coming into contact with the human body. Therefore, efforts have been made to reduce accidents caused by electric shock and electrical leakage. On the contrary, the “capacitive touch screen technology” is a new technology that utilizes the fact that the human body is a conductor.
Touch screen technologies include pressure-sensitive, capacitive, infrared, and ultrasonic technologies. In the early days of touch screens, pressure-sensitive technology was widely used. Pressure-sensitive technology receives input from the pressure exerted by a person pressing the screen, so it has the disadvantages of being less durable and unable to implement multi-touch. Therefore, “capacitive” touch technology is widely used in recent smartphones and tablet PCs. Electronic products with capacitive touch technology have sensors in the form of electrodes attached to the four corners. When a person touches the screen, electricity flows from the person’s body, which is a conductor, and reaches the sensor. The intensity of the current received by the sensor varies depending on the position touched and the distance to each sensor. Through this, the sensors can read the exact coordinates. In this way, the device can receive various inputs based on the coordinates read.
With the rapid growth of the smartphone and tablet market, capacitive touch screen technology is also evolving, with thinner conductive films to reduce weight and lower power consumption for longer battery life. Currently, touch screens are mainly used to change the input method of existing electronic devices. However, as touch screen technology continues to advance, it is expected that many products with touch screen functions will appear in the future, such as windows, shower rooms, and portable IT devices made of a single sheet of glass.
