Turn anything to a Touch Screen with a can of Spray paint!

Written by: Meghna KT

How does a touch screen actually work?

The touch screen is a piece of technology that seems to be everywhere. But, how does a finger touch make a smart gadget work? In general, there are two types of touch screens- Resistive and Capacitive.
Resistive touch screens are mostly used in ATM’s and supermarkets. On pressing hard, the screen bends slightly. This in turn disrupts the electric charges on the screen. Due to this pressure, the resistance of the screen changes. The area which shows a change in resistance, refers to the point of touch. Capacitive touch screens work on a totally different principle. The human skin is the conductor here! Our skin consists of positive and negative ions. This electric charge on the screen gets disrupted when it senses a touch. One need not apply pressure to disturb the alignment of the charges. When connected to a computer, the location of the touched part can be seen (i.e. there is loss of charge in the location).
Based on this principle, industries have been formulating various ideas. Ever wondered how? Imagine converting your walls and furniture into a touch screen by using a can of spray paint. Dubbed as ‘ELECTRICK”, researchers at the Carnegie Mellon University have come up something called- “Spray-On Touchscreens”!

The theory behind their ‘Trick’

Electrically conductive materials are most often used in sensing. Applying a coat of this spray on any material does the ‘trick’!
“For the first time, we’ve been able to take a can of spray paint and put a touch screen on almost anything” said Chris Harrison, assistant professor in the Human-Computer Interaction Institute (HCII) and head of the Future Interfaces Group.

Electric Field Tomography

In its simplest sense, Electric field tomography is a technique used for imaging various objects. Various electrodes are placed on the object that is to be sensed. The process uses two main electrodes- The transmitting and receiving electrodes. A constant voltage or supply to given to the transmitting electrode. A voltmeter is a sensitive device which measures the voltage picked up by the electrode. The output is then fed to the receiving electrode. The voltage generates a series of electric field lines. These lines cut the object under study and the picture is then seen on a monitor.

How is the sensing effect achieved?

An electric current of a few amperes is introduced into the conductive layer using electrodes.
The orange dots in the figure correspond to the electrodes placed on the surface. When a person places his/her finger on the surface, the electrodes pick up the voltage. The position of the finger can be located by observing the electrodes which emit the current. By using tomographic techniques, the location is detected. This unique sensing mechanism gives Electrik its ‘X-Factor’!

Electrik: Can it be applied to any kind of material?

The concept of Electrik can be applied to three classes of materials: Solids, Pliable and Paintable. Even your phone covers can be made into a virtual touch screen! The various grips on the phone case show different kinds of motions. One can also spray conductive carbon on toys and Jell-O to create Electrick. On touching various areas of these toys, a varied range of sound stimulations can be heard. Velostat is a material which is commonly used for the packaging of electronic good. One can paste velostat sheets using adhesives to create low-cost touch panels.

The versatility of Electrick

Some methods rely on computer vision for detection of a touch. This process can be disrupted if the camera’s vision on the surface is blocked. The presence of cameras also raises the bar when it comes to matters of privacy. Electrick completely overcomes the above disadvantage. Electrick is accessible to hobbyists and can be applied to common manufacturing techniques.
Incorporating touch sensing in objects with irregular geometry can be taxing and expensive. The versatility of Electrick lies in converting unsymmetrical objects into touch screens. With the prices of mobiles and touchpads soaring high, the concept of Electrick looks promising.
To prove the uniqueness this technology, scientists applied the concept to objects used in day-to- day activities.
Musical Instruments: “It’s possible to play the guitar without strings.” Yes! You heard that right. The user can add virtual controls to the surface of the guitar by using a drag and drop an application on his computer. The touch tracking is achieved by carbon spraying the guitar.
Even a play-doh snow man can be made interactive! Electrick has a lot of potential applications. With Electrick, an entire wall can be touch sensitive. It can be used to control the intensity of various light bulbs and electronic devices at once. So, one need not worry about electrical wiring and insulation of the same anymore!

Can Electrick replace the touch technology in the future?

The durability of Electrick is a point to ponder on. Environmental noise can affect the performance of this device. The conductive coating on the object acts as an antenna causing distortion. The human touch adds to the noise created by the device. The concept of grounding the current raises another issue. The combined grounding of the sensor and the user completes the circuit.It is difficult to detect currents in small devices. Thus, the concept of Electrik has a lot of modifications to be made. This low-cost effective solution can possibly be used as a touch interactive computer in schools and colleges for educational purposes.

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