1. SEAS
TECHTILES: A MEASUREMENT SYSTEM IN CLOTHING
Will Gottschalk, Aamir Husain, Leo Parsons, Mentor: Dr. David Nagel
The George Washington University, School of Engineering and Applied Science,
Department of Electrical and Computer Engineering
Three sensors used for data acquisition:
• 2 Lead Electrocardiogram (ECG)
• 2nd order, 250 Hz Low Pass Filter
• Fabric (Silver coated nylon) electrodes
• Stretch Resistor
• 2nd order, 100 Hz Low Pass Filter
• Constructed with Silver coated nylon bands
• Accelerometer
• Triple axis, +/-3g
• Improved circuit design to handle more movement
• Smaller housing and less wires
• Activity history and analytics
• Cross-platform implementation
• More robust algorithms for higher accuracy and
better data analysis
MOTIVATION
Technology has become an increasingly integral part
of our daily lives, and people want the ability to
know more about their biometric data in a
comprehensive and simple way. While there are
products today which can accomplish some of this
data, there is still not a stand-alone product which
can cover a wide range of biometrics. The goal of
this project is to create a device which measures
these various biometrics in a practical fashion.
INTRODUCTION
SENSORS
CONDUCTIVE FABRIC & THREAD
• Silver coated nylon and stainless steel thread were
chosen for their low resistance
• Allows the shirt to be entirely washable without
destroying electrical components
• Used to construct stretch resistors, ECG electrodes,
and wiring within the shirt
SOFTWARE DESIGN
MECHANICAL & 3D DESIGN
REFERENCES
Physiological monitoring has become
increasingly popular with the
availability of advanced technology.
The wearables technology market is
PRINTED CIRCUIT BOARD DESIGN
Techtiles is a fully functioning prototype which is
potentially just a few more steps away from
commercialization. While the wearables market is still
growing, there is ample time to improve the product
and make it marketable to a wide variety of fields
such as healthcare, fitness, and military technology.
The Techtiles team would like to give a special
thanks to Dr. Nagel, their Senior Design mentor, as
well as all the other mentors who helped make this
project a reality.
Critical Decisions:
• Designed with surface mount components to
reduce overall size
• Input leads for stretch resistor and ECG located in
one area for easy connection to the shirt
• Open footprints for addition of Bluetooth module,
micro controller, and accelerometer
CONCLUSIONS
FUTURE WORK
DESIGN OVERVIEW
System is composed of three individual subsystems:
• Sensor Integration
• Data Processing
• Android Application
System Requirements:
• Detect physiological signals
• Automatically pair with and transmit data to a
mobile device
• Display heart rate, breathing rate, steps taken,
distance traveled, and energy expended on a user-
friendly mobile app
• Comfortable to wear for long periods of time
• Battery life of at least 5 hours with continuous
monitoring
• Housing is designed specifically to incorporate
PCB, battery, battery charger, accelerometer,
power switch
• Slidable cover to access components
• Pegs to secure charger and PCB in place
• 3D-printed in ABS plastic
• ABS plastic can be melted down and reused
RESULTS
The finished device was tested by comparing values
displayed on the mobile to values given on a
performance treadmill.
FINAL PROTOTYPE
• Algorithms use pre-defined thresholds determined
from incoming data to extract information about
steps, heart rate, and respiration rate
• Energy expended is calculated using a data set
relating energy burned with speed
• Distance is determined by using step count data
and stride length based on a user-defined height
[1] "Wearable Device Market Value 2010-2018 |
Forecast." Statista. N.p., n.d. Web. <http://
www.statista.com/statistics/259372/wearable-device-
market-value/>.
expected to nearly double to $12.6 billion by just
2018 [1].
Techtiles aims to consolidate sensors which are
normally not found together on one singular device.
The main purpose of this device is to monitor a
user’s heart activity, breathing and movement, and
then process that data to compute heart rate,
respiration rate, steps taken, distance travelled, and
energy burned.
Bio
Sensors
Processing
Mobile
Display
Analog Signals Wireless Data
Figure 1: Basic System Overview
Figure 2: Techtiles Circuit Diagram
Figure 3: PCB Design Figure 4: Populated PCB
Figure 5: Software Flow Diagram
Figure 6: 3D Designed Housing with Battery (red) & PCB (green)
Step Accuracy:
4 steps
Energy Accuracy:
0.27 kcal
BPM Accuracy:
17 beats/min
Distance Accuracy:
7.1 feet
Respiration Accuracy:
10 breaths/min
Figure 7: Shirt front (left) and back (right)
Figure 8: Completed Housing
with connecting sockets
Figure 9: Techtiles App
Stretch Sensor
ECG Electrodes
Housing
(Battery, PCB,
Accelerometer)