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Introduction

Wearable technology has become a vital part of our life and established itself as an evolving

product category. A Mechatronic or say, Smart Shoe can be a really important device to keep

track of many things in our daily life such as health monitoring, location tracking and various

other indications. The smart shoe with many electronic devices integrated into it can be used as a

regular need in ones life.

Smart Features

Auto adjusting, self-tightening technology to fit the shoe with any person having different

shoe-size.

Water proof material to make the shoe safe from liquid as well as dirt.

Measure the distance travelled using accelerometer.

Location tracking using GPS module embedded into it.

Direction indicator in the form of vibrations.

Proximity alert as soon as the wearer is out of range from his Smartphone.

Rechargeable solar battery with a stylish flexible solar panel on the shoe.

Identify owner by measuring his weight using Load cell and checking the owners

identity using iBeacon technology.

Fig.1 Features of Mechatronic Shoe

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Material Used

The mechatronic shoe can be made auto-adjustable by using the build material of the shoe that

has the property of expansion and contraction. The material to manufacture shoe can be Electro

Active Polymer (EAPs).

Electro Active Polymer exhibit change in its size and shape when comes under the

influence of Electric field. The actuation in EAP is caused by electrostatic force between

the electrodes which squeeze the polymer.

Once the shoe material is either expanded or contracted, no additional electric power is

required to keep the material in its place.

EAP is highly tough, and can withstand large actuation strain, therefore it is used as a

constructive material for shoe.

Besides toughness, there are other properties also required for the shoe. One of the most

important properties is water-proof. A separate layer of Super-hydrophobic coating ensures that

the shoe will be water proof.

Superhydrophobic coating is a nanoscopic layer that repels water.

The coating can be made from various chemicals such as Manganese oxide polystyrene

(MnO2/PS) , Zinc oxide polystyrene (ZnO/PS), Precipitated calcium carbonate, and Silica

nano-coating

A thin layer of this coating avoids water as well as other liquids from clinging to the

surface of the shoe.

This coating can be layered on to the top of our flexible solar panel to avoid damage to it.

Also the superhydrophobic layer is available as a transparent material.

Health monitoring

The users or wearer activities can be determined by the device accelerometer.

Accelerometers measure linear acceleration and tilt angle. A multi-axis accelerometer detects the

combined magnitude and direction of linear, rotational and gravitational acceleration. They can

be used to provide limited motion sensing functionality.

The accelerometer is interfaced with a microcontroller using I2C interface. The microcontroller

to be used may belong to any family from 8051, Atmega, PIC or ARM. Since ARM is one of the

latest and high-end processor, therefore it is wise to use ARM microcontroller that have a high

processing speed along with many peripheral interfaces. The microcontroller will be fitted on to

the sole as shown in Fig.2.

The various specifications of the accelerometer have to be controlled for proper operation. As the

accelerometer used will be 3-Dimensional, thus its dynamic specifications such as sensitivity,

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tolerance in measurement, electronic noise, peak amplitude, and temperature range should be

controlled.

The output voltage by the accelerometer will be in the range of millivolts (mV). The

typical temperature range of working is 50C to 120C.

The accelerometer can be embedded into the shoe to measure the amount of time the

users foot is on the ground, which is inversely proportional to speed. The device

transmits signal at 2.4 GHz to a receiver that can be either attached to a Smartphone.

The sneakers can also count the number of steps taken, distance travelled. The number of

steps travelled can be measured using the load cell reading, as whenever a step is taken,

pressure will be put onto the Load cell. So the total number of readings from both the foot

can be calibrated in terms of number of steps taken.

Using GPS and motion-sensing technology that's already built into our phone, it

figures out how much we are moving throughout the day, and what kind of

movement it is. It then keeps track of those activities, adds them all up, and weighs

them against a goal we have set for ourselves.

A Load cell can be embedded into the sole of the shoe, and integrated with the

Smartphone. The Load cells data can also be used to identify the owner to avoid

theft. In this case, weight of the wearer acts as his identity. A 5% tolerance can be

provided in the data measured by the Load cell.

The Load cell is also interfaced with the microcontroller. There is no special

interface required for the Load cell, and its readings have to be converted to digital

form using a ADC (Analog-to-Digital Converter) that is already present in the

microcontroller.

A model of sole of our smart shoe created in Creo Software shows the placement of

various electronic modules in Fig.2.

Fig.2 Electronic modules placed on the sole of the shoe.

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The identity of the owner is confirmed using load cell along with iBeacon

technology.

iBeacon also called as Bluetooth Smart works on Bluetooth Low Energy (BLE). It

uses Bluetooth low energy proximity sensing to transmit a universally unique identifier

picked up by a compatible app on our Smartphone.

The identifier on receiving can be matched with the identity of the owner, so as to use

this identity as an anti-theft protection. The Bluetooth module is fitted on the back of the

shoe as shown in Fig.3.

The Bluetooth module is also connected to the microcontroller using Universal

Asynchronous Receiver /Transmitter. The baud rate can be set which denotes the transfer

speed of the data. The module to be used can be HC-05 that is able to act both in master

mode and slave mode.

Fig.3 Bluetooth module fitted at the back of the shoe.

Location Tracking

The smart shoe can be used as a tracker for determining the position and location of those whom

we care about. A GPS enabled circuit can be embedded into the sole of the shoe as illustrated in

Fig.4 that sends the location of the wearer.

The GPS module is connected to the microcontroller using UART interface only. The GPS

module transmits the data in the form of string serially that is in the form of NMEA developed

by National Marine Electronics Association. The string contains all the details in a fix order that

has the corresponding latitude and longitude of the current location.

The smart shoe can also be used to give directions to the wearer. A detachable Bluetooth

transceiver is embedded into the shoes, which links to the Smartphone app. The app

directs the user using Google maps and sends a vibrating signal to indicate left or right

turn.

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The vibrator module can be embedded on the side of the shoe as shown in Fig.6.

Vibrator modules are nothing but coin size vibration motors, also known as shaftless or

pancake vibrator motors. The size of the motor is in the range of 8mm and 10mm

diameter. These are compact and convenient to use.

The motors can also be interfaced with a simple General Purpose Input/Output (GPIO)

pins of the microcontroller.

The user can set the source and destination of where he wish to go on the Google map,

and as he starts to walk on the road, the shoe would indicate in which direction he needs

to go to reach the destination. Lets say, wearer needs to go to right side, then in this case

his right shoe would vibrate.

Fig.4 GPS module on the heel of the shoe

As the shoe is linked with a Smartphone for its functioning, hence a proximity alert can

be set using either a Bluetooth or a Transmitter-Receiver pair so that, if we go away from

our phone, both the shoes starts buzzing as a warning.

With the help of GPS technology, if someone wearing shoe has wandered off, then his

guardians can locate the wearer using a website which shows the exact location of the

wearer.

The shoe is helpful for keeping an eye on an Alzheimers patient to track the location

from afar via an online viewing portal. We can track their location through any

Smartphone, tablet or web browser, set up text and e-mail alerts if they leave or enter

defined areas on a map. The working and tracking process is illustrated in the form of

diagram in Fig.5. As the GPS module uses the data from the satellite, hence it is

convenient when a user is in open environment.

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Fig.5 Working of GPS

Battery

For any electronic device to work, an efficient power source is required. The power source we

can use is mini-flexible solar panel that covers the periphery of the shoe. A Solar Fabric can be

used that converts light into Electricity, and charges built-in solar powered battery. Solar

modules use light energy (photons) from the sun to generate electricity through the photovoltaic

effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based

on cadmium telluride or silicon. Semi-flexible ones are available, based on thin-film cells.

Flexible thin film cells and modules are created by depositing the photoactive layer and other

necessary layers on a flexible substrate.

The cells are assembled into modules by laminating them to a transparent colorless

Flouropolymer on the front side (typically ETFE or FEP) and a polymer suitable for

bonding to the final substrate on the other side.

The only commercially available flexible module uses amorphous silicon triple junction.

Flexible thin-film panels are optimal for portable applications as they are much more

resistant to breakage than regular crystalline cells. They are also much lighter per square

foot than standard rigid solar panels.

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Fig.6 Sectional side view of shoe showing vibrator and Solar Panel Covering.

Thus, this kind of flexible solar panel sheet can be used in the construction of the shoe. Hence,

there would be no problem of battery when the user is outside and in an open environment

provided sunlight is there. The flexible solar panel can be designed so that it can be used as the

covering and outer material on the vamp and toe-cap of the shoe. This is illustrated in Fig.6. A

USB charging socket can also be provided to charge the battery stack if the location of wearer is

not in tropic zone. The charging socket can also be used for first time charge of the battery.

Advantages

The ergonomic electronic devices slide into shoes and feel like regular insoles.

Monitor the shoe wearer on the go with either online mapping portal or Smart Locator

app.

Helpful for visually challenged people as it would work without any audio or physical

distractions.

Cellular technology enables connectivity wherever 2G GSM coverage is available.

2-3 day battery life when full charged with normal use ensures we are connected when

we need it most.

References:

1. Giulia Orecchini, Li Yang, Manos M.Tentzeris, Luca Roselli, Smart Shoe: an autonomous

inkjet-printed RFID system scavenging walking energy, IEEE, 2011. 2. D. Simsik , A. Galajdova , M. Gorlicky , and R. Balog, The mechatronic shoe: A new

rehabilitation tool for improving mobility. 3. Wikipedia Pages- IBeacon, Electroactive polymers, Superhydrophobic coating, Solar Panel.