University of Alicante

The present invention consists of a device capable of receiving an electrical signal from a conductive cement-based material (pastes, mortars and concretes) which, due to changes in electrical resistivity when pressure is applied, pre-amplifying and transforming it, allows the cementitious material itself to act as an electrical switch.

With the measurement of the deformation of the cementitious material, new applications can be developed, including, for example, providing the traffic network of a city with smart materials that warn drivers that a pedestrian is approaching a sidewalk with the intention of crossing the road (Smart City concept).

In this sense, a switch system has been developed that warns of the presence of an object and/or individual close to a certain area by emitting an acoustic and/or light signal.

This switching system (see Figure 1) consists of, at least:

• A sensor whose electrical resistance changes when subjected to mechanical stress or strain. This piezoresistive pressure sensor is prismatic in shape and is located adjacent to the area of interest.

• A cementitious composite consisting of cement, aggregates, water, additives, and a hybrid mixture of carbon nanotubes and expanded graphite that is configured to provide the first electrical output signal in response to the deformation of the material in which it is contained, whose signal is a function of the variation of the electrical resistivity of the material itself.

• Two electrical electrodes distributed in levels or layers within the same sensor, which are electrically powered from a power supply source of direct current electrical energy at a constant intensity.

• An electronic evaluation circuit that receives the first electrical output signal and provides as output, a warning signal to the target object and/or individual.

• Two evaluating electrodes distributed in a stacked configuration in levels or layers arranged between two layers adjacent to electrical electrodes, which are electrically connected to the evaluating electronic circuit.

• A comparator amplifier that receives the first electrical output signal + a reference electrical signal (from a reference electronic circuit) that provides a second electrical output signal, if certain requirements are met. This comparator circuit provides an output voltage that is used to turn on or off the warning signal provided, for example, to the vertical traffic signal associated with a zebra crossing, by illuminating it or keeping it off.

Figure 1: basic schematic of the electronic circuit capable of receiving the signal of the variation recorded in the conductive concrete and emitting a new signal. The characteristics of the electronic components vary according to the conductivity of the concrete and the type of signal to be emitted.

ADVANTAGES OF THE TECHNOLOGY

The main advantage of this invention is the practical implementation of the theoretical concepts based on the perception of the deformation or piezoresistivity of cement-based materials with addition of carbonaceous materials with conductive properties.

This innovative device is characterized because it is sustainable and environmentally friendly.

INNOVATIVE ASPECTS OF THE TECHNOLOGY

The object of the present invention combines previous knowledge regarding the manufacture of cement-based materials (capable of sensing their own deformation) with electronic devices capable of making feasible the practical use of this property.

To date, no device has been found on the market that can transform the variation in the electrical properties of the material into a signal capable of being implemented in a practical application.

The technology has been successfully developed at laboratory scale, and is at Technological Readiness Level (TRL) = 4.

The circuit can be designed for different types of variables and parameters.

As an example, the technical feasibility of the invention has been tested by applying 50 mA across three resistors of 75Omega to a prototype. The minimum mechanical pressure was set to 80 kg. The voltage set by the potentiometer is 1KOmega (minimum 20 micro volts). A 220V 40W light bulb was activated. The whole circuit was powered by a 220V ACac input and 9Vdc output power supply.

This innovative device allows multiple applications related to the development of smart sensors in civil infrastructures, such as:

• Switching on streetlights when vehicles or people pass by.

• Activating acoustic and/or light signals in the event of dangers (pedestrian crossings, over-heavy vehicles, etc.).

• Modifying the sequencing of traffic lights according to the flow of vehicles.

• Activate safety systems installed in traffic lanes.

• Other applications of interest....

Thanks to the development of electronic devices for the reception and transformation of the signal received as a result of the variation in the electrical properties of the material, it is possible to subsequently use it as an open/closed circuit in different practical applications.

These applications are included in the Smart City concept.

Companies interested in acquiring this technology for commercial exploitation through utility model licensing agreements are sought.

Company profile sought:

• Manufacturers of smart sensors.

• Manufacturers of multifunctional conductive cementitious materials

This invention is protected by a utility model application:

• Utility model title: "Un sistema conmutador de aviso".

• Application number: U202132323.

• Application date: 23^th November, 2021.