Overview
Many people use mobile phones, and most of those devices are smartphones. Two touchscreen technologies are most common today: capacitive and resistive. The following compares their structures, principles, and characteristics.
Capacitive touchscreens
Capacitive touchscreens are typically constructed as a four-layer composite: an outer glass protective layer, a conductive layer, a non-conductive glass layer, and an inner conductive layer. The innermost conductive layer serves as a shield for internal electrical signals. The intermediate conductive layer is the key sensing element; traces at the four corners or along the edges connect to it and are used to detect touch position.
Resistive touchscreens
Resistive touchscreens, often called "soft screens," were common on older Windows Mobile devices. Capacitive touchscreens are sometimes referred to as "hard screens" and are used by devices such as the iPhone and early Android models.
Comparison
1. Indoor visibility
Both technologies generally provide acceptable indoor visibility.
2. Touch sensitivity
Resistive: Requires pressure so that layers make contact. It can be operated with a bare finger (including gloved fingers in many cases), a fingernail, or a stylus. Stylus support and handwriting recognition remain important in some markets.
Capacitive: Even the slightest contact from a charged fingertip can activate the capacitive sensing system. Inanimate objects, fingernails, and most gloves are ineffective, and handwriting recognition is typically more difficult.
3. Precision
Resistive: Positioning precision can reach the level of individual display pixels, which is useful for stylus input and interfaces with small controls.
Capacitive: Theoretical precision can be a few pixels, but in practice precision is limited by the contact area of the finger, making it difficult to accurately tap targets smaller than about 1 cm2.
4. Cost
Resistive: Generally low cost.
Capacitive: Typical prices are 10% to 50% higher than resistive panels. The extra cost is usually acceptable for flagship devices but can be a deterrent in the mid-range segment.
5. Multi-touch capability
Resistive: Native multi-touch is generally not possible without redesigning the sensor and electronics.
Capacitive: Multi-touch support depends on implementation and software; it has been demonstrated on several devices and is commonly supported on modern capacitive panels.
6. Durability
Resistive: The top layer must be flexible to allow pressure-based contact, which makes it more susceptible to scratches. These screens often require a protective film and more frequent calibration. Devices using plastic layers can be less prone to breakage from drops.
Capacitive: The outer layer is usually glass. While glass can crack under severe impact, it resists daily abrasion and smudging better than soft plastic layers.
7. Cleaning
Resistive: Because stylus or fingernail operation is possible, these screens are less prone to fingerprints and oil deposits.
Capacitive: Requires finger contact, but the glass surface is easier to clean.
8. Environmental tolerance
Resistive: Specific operating limits vary by design, but some resistive devices have been shown to operate across a wide temperature range (for example, -15°C to +45°C) and with less sensitivity to humidity.
Capacitive: Typical operating temperature ranges are narrower (for example, 0°C to 35°C) and minimum humidity requirements can apply due to the sensing principle.
9. Sunlight visibility
Resistive: Visibility in bright sunlight is often poor because the additional layers increase surface reflections.
How they work
Resistive touchscreen: Multiple transparent conductive layers are used. Two transparent conductive metal layers detect pressure from a stylus, fingernail, or any hard object. Under normal conditions the two conductive layers are electrically insulated from each other. When pressure causes the top conductive layer to deform and contact the bottom layer, a conductive path forms. Because there is electrical resistance between the two layers, a constant voltage (for example, 5 V) applied across the layers is reduced at the contact point. The touchscreen controller measures this voltage drop and converts it to coordinates to determine the touch location.
Capacitive touchscreen: The human body, the fingertip, and the screen form a coupling capacitance. This coupling transmits high-frequency current signals from the body. Electrodes distributed at the corners or edges of the screen receive the high-frequency signals conducted through the fingertip. Because the signal amplitude varies with touch location, comparing the signals from multiple electrodes allows the controller to calculate the touch coordinates.
Precision and sensitivity
Resistive: Compared with capacitive screens, resistive screens can offer higher pointing precision because the conductive path forms at a very small contact point, potentially down to an individual pixel. However, resistive sensing requires sufficient pressure, and uneven pressure can interrupt recognition, so sensitivity is lower than capacitive.
Capacitive: The bioelectric signal is distributed across the fingertip surface, so input is spread over an area covering multiple pixels. A finger does not need to press firmly to register a touch, which increases sensitivity, but the contact area can cause positional drift, so capacitive panels are not necessarily superior in raw precision.
User experience
Resistive: The voltage-drop based coordinate calculation means resistive screens cannot report the coordinates of multiple pressure points simultaneously, so they do not support multi-touch natively.
Capacitive: The distributed current sensing can register input from multiple coordinates, enabling multi-touch interactions. Multi-touch capabilities have enabled a range of new interaction patterns in software and generally enhance the user experience.
Cost and maintenance
Resistive: Mature manufacturing processes, established supply chains, and common use in earlier devices result in low cost and easy availability of repair parts, which simplifies maintenance.
Capacitive: Production cost is typically 10% to 50% higher than resistive. Early adoption was concentrated in high-end products, where consumers accepted the premium, but higher cost has been a barrier for some mid- and low-end device segments.
Which is better?
Capacitive screens are more sensitive and support multi-touch, and they are now the dominant choice for high-end smartphones. Their operating principle relies on changes in capacitance caused by a fingertip; they typically feature a hard glass surface and require little or no pressure, but they generally work best with bare fingers.
Resistive screens rely on pressure to change resistance between layers; they have a soft feel with slight depression when pressed, can be operated with any stylus or gloved finger, and are often less expensive. However, resistive panels do not natively support multi-touch and are more prone to surface wear and scratches.
