Abstract— A widespread requirement exists for a low costand reliable health monitor in the clinical as well as homeenvironment. The e-jacket presented here is an example of asmart clothing system with multiple bioparameter acquisition ofelectrocardiogram (ECG), pulse oximetry, body motion/tilt andskin temperature. The battery operated circuit has anintegrated graphic liquid crystal display (LCD) screen and a2.4GHz wireless link. An RS232 interface provides a plug-inport for easy accessibility to remote telemedicine applications.The system incorporates an efficient ARM7 microcontroller tocoordinate a list of software tasks with associated time stamp.Comfort analysis and reliability aspects have been carefullystudied along with intelligent power conservation schemes. Alow cost and reliable tele-medical network is proposed using aninnovative e-textile solution.

I. INTRODUCTION

odern electronics, in conjunction with state-of-the-artsensors, can provide novel solutions in medical

diagnosis and mobile health care system. Smart garments arethe future clothing systems with intelligent electronicsembedded in the fabric.

We strive to add an efficient and miniaturized wearablecomputer into an existing woolen jacket. A jacket is heavieras compared to a shirt or a vest and the miniaturizedelectronics may easily hide without causing inconvenience tothe subject. Non-invasive techniques are adopted for vitalsign recording. The e-jacket embeds a three channelreconfigurable twelve lead ECG amplifier, aphotoplethysmograph (PPG) for pulse oximetry, anaccelerometer for motion/tilt detection, and a temperaturesensor for skin temperature recording. The sensors and thesignal conditioners are interfaced to an ARM7microcontroller LPC2138. A wireless transceiver and anLCD are also connected to the same processor. The localhost may be a base station or a personal computer (PC). Auniversal serial bus (USB) to radio frequency (RF) bridgecircuit is adopted along with another LPC2138 at the localhost side for effective communication with the e-jacket. Thelocal host is equipped with a telemedicine support through amodem link to a remote server. The physical status of thesubject is monitored continuously and relayed to the localhost wirelessly, which in turn, passes to the remote patientdatabase. The physician may retrieve and analyze the storeddata at the remote end, whereas, the patient may be at home.

II. DESCRIPTION

Figure 1a shows a woolen jacket, with a pulse oximetryprobe on a fingertip and an LCD stitched in the front side.The printed circuit board (PCB) and a lithium ion batteryreside in the pocket firmly. The temperature sensor is placedon the inner wall of the jacket, near left arm shoulder joint.The sensor carries four wires that are mostly hidden insidethe stitches of the inner lining, as depicted in figure 1b. Thefive ECG electrodes use standard gel based adhesive strapsand need to be placed at the chest (V), left arm (LA), rightarm (RA), left leg (LL) and right leg (RL). These are alsomarked on the plastic cover of the cables. The 3-axisaccelerometer is pasted on the PCB. To ensure a reliable tiltmeasurement, the PCB is firmly locked in the pocket, so thatonly body movement is detected. The wireless daughter cardis also plugged onto the main PCB.

A. E-jacket hardware

Figure 2 presents the generalized block diagram. Size andpower consumption are important design parameters. Thewoolen jacket is embedded with off-the-shelf hardwarecomponents in surface mount (SMD) form factor.Micropower ICs in the circuit minimize the powerconsumption significantly.

A three-channel electrocardiogram amplifier has been usedto acquire cardiac signals. The leads are reconfigurableunder software control except for the V-lead. A combinationof lead 1 (LI), lead 2 (LII) and chest lead V5 is mostlyrequired and the present jacket supports this configuration,along with others.

Pulse oximetry works by applying a photo sensor to apulsating atriovascular bed, in a finger, toe or ear lobe, usinga photoplethysmograph (PPG) probe. The manually preparedprobe consists of an ultra bright red LED and an infraredLED along with an OPT101, a monolithic precisionphotodiode and transimpedance amplifier. A band pass filterof 0.5 Hz to 5 Hz reduces high frequency interference. Thered and infrared LEDs are selectively turned ON one at atime. The corresponding response is sensed, filtered,converted into digital form and sent wirelessly to the localhost. The host accumulates the data and oxygen saturation inblood is calculated using the following empirical formulas[1]

( / )

( / )

AC DC RED

AC DC IR

I IR

I I= (1)

Wireless E-Jacket for Multiparameter Biophysical Monitoring andTelemedicine Applications

Sudip Nag*, Dinesh K. Sharma**,Electrical Engineering Department, Indian Institute of Technology Mumbai, India

*sudip@ee.iitb.ac.in, **dinesh@ee.iitb.ac.in

M

400-7803-9787-8/06/$20.00 ©2006 IEEE

Proceedings of the 3rd IEEE-EMBSInternational Summer School and Symposium on Medical Devices and BiosensorsMIT, Boston, USA, Sept.4-6, 2006

(2)

where, εHbO2 and εHb are extinction co-efficients ofoxygenated and deoxygenated hemoglobin, s is the oxygen

saturation level or SpO2 , λR and λIR are the wavelength ofred (650nm) and infrared (850nm) LEDs.

Tilt or acceleration is sensed using a three axis selectableG accelerometer MMA7260. The 1.5g mode yields anapproximate sensitivity of 800mV/g and is adequate forambulatory cases.

A semiconductor temperature sensor LM92 is selected forbody temperature measurement. The IC has an on-chipsensor with ADC and can stream the calibrated data

in 2’s complement form.2.4GHz direct sequence spread spectrum transceiver chip

CYWUSB6935 enables the jacket to work in wireless mode.It is a serial peripheral interface (SPI) to antenna bridge withon-chip pseudo code correlators. Matched PCB trace wiggleantennas provide a reliable range of 20m approximately at0dbm power level. The microcontroller forces the RFcircuitry in power down mode during analog conversions toreduce power consumption and to avoid RF noise.

An RS232 port is added to test the functionality at aminimal overhead. The MCU responds to a predefinedcommand set from the local host and actuates the requestedoperation.

The summary of vital signs of the wearer is displayed on achip-on-glass based monochrome LCD. A rechargeable 3.7V850mAh lithium ion battery powers the jacket circuitry.BQ24010 battery charger and TPS77633 low dropoutregulator forms the hardware power management scheme.

The host side hardware consists of Wireless-USB likeradio link with a CYWUSB6935 transceiver, LPC2138controller, and USB-to-UART bridge CP2102. The circuit ispowered from the USB itself and a virtual communicationport driver is installed in the host computer.

Double-sided FR4 glass epoxy PCBs are used for low costand reliable mixed signal performance. The components aremounted using hot air assembly technique and by normalhand soldering. Figure 3 depicts the hardware.

B. E-jacket software

The C code for the microcontroller is developed usingGCC and consumes 19.2KB of flash and 15.1KB of SRAMspace. The data memory or SRAM buffers three ECGchannels, three accelerometer axes, red and infrared data forPPG, and skin temperature.

The microcontroller initializes each peripheral at startupand waits for a valid command. The jacket acquires thephysiological data and the summary is wirelessly transmittedto the host unit at 1second intervals. 512 bytes buffer isallotted to each channel. The MCU packetizes the data andtransmits it to the host while the buffer is filled. The hoststation is expected to have remote communication link with anetwork stack for a telemedicine link. The doctor or

Figure 3(a). Hardware for e-jacket(b). Wireless transceiver with USB port for local host.

(b)(a)

a

(a)

Figure 1(a). Outer view of e-jacket with PPG probe and LCD(b). Inner view with temperature sensor and ECG

electrodes

(b)

( ) ( )

( ) 2( ) [ 2( ) ( )]

Hb R Hb IR Rs

Hb R HbO R HbO IR Hb IR R

ε λ ε λε λ ε λ ε λ ε λ

−=− + −

ARM7MCU

3-Channel(Reconfigurable) 12-Lead ECG Amplifier

3-Axis(Selectable G)Accelerometer

LEDs (Red & IR)with Photo Diode +Transimpedance

Amplifier

High AccuracyTemperature Sensor

2.4GHz RFTransceiver

RS232Transceiver

Graphic LCD(84×48 pixels)

PowerManagement

Figure 2 (a). Functional Block Diagram of e-jacket hardware.(b). Local host side RF-to-USB bridge.

2.4GHz RFTransceiver

ARM7MCU

USB-UARTBridge

USBport

(a)

(b)

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Figure 4. A telemedicine scheme.

nurse may login to the jacket remotely and visualize thedata.

The SPI bus is shared among the RF transceiver and LCD,and thus a reconfiguration routine activates every time whilethe controller switches among the mentioned peripherals.The process is absolutely transparent to the user duringnormal operation of the jacket. The temperature sensorLM92 is interfaced through I2C bus in slave mode.

Software power management technique is utilized mainlyfor RF and PPG setup. The RF transceiver is switched offafter each radio transaction. The PPG LEDs are turned offwhile the oximetry is not required.

Interrupt based software architecture is used to realizethreaded operation among the given pool of tasks.

III. OPERATION

A smart garment must be easy to operate, yet facilitateintelligent features at minimal overhead to the user. Thesubject should wear the e-jacket and ECG electrodes must bestrapped at the indicated locations. PPG probes need to beplaced on the fingertip of either hand. The accelerometer andthe temperature sensor require no additional adjustment. Aspecific command is issued from RS232 or RF link to startrecording of the bioparameters.

The temperature sensor senses the skin temperature at eachsecond and is triggered by the real time clock interrupt. I2Cstart condition is sent to the LM92 sensor and the successiveinterrupts are serviced. The command-based approachcontrols recording, streaming and other calibrationadjustments, and the wearer may not be aware of alloperational details.

A custom data format is used to wirelessly transmit andsegregate each jacket wearer through a coded identificationnumber. Thus, in a clinical environment, it is easy to networkseveral subjects wearing similar jackets. This is incorporatedto create a mass medical database generation for diagnosticapplications.

Physical switches are avoided to free the wearer from anyadditional learning requirements. Rather, a nurse in a clinicor caretaker at home may start the operation, in case thesubject is terribly sick and requires continuous monitoring. Acustom graphical user interface on Visual Basic platform hasbeen developed to display the acquired waveforms on apersonal computer screen.

IV. DESIGN ISUUES

The e-jacket is intended to be used in variedenvironmental conditions. Embedded design in the jacketfaces a trade-off between low power, low cost and highperformance features. The presented design selects a highperformance and low cost microcontroller with a reasonablygood mixed signal peripheral set and a large on-boardmemory. DSP algorithms are expected to run in the core ofthe successive versions.

Unlicensed industrial scientific and medical (ISM) bandRF communication is chosen for easy adaptability and easyimplementation.

A. Telemedicine Approach

The e-jacket is supported by a set of smart features fortelemedical functionality. The RS232 port may be pluggedinto an ultra-small modem for remote link using the existingpublic networks. The medical personnel may monitor thesubject remotely and upload the physiological informationfor analysis. Since the accelerometer provides the orientationinformation of the wearer, the software interface may beprogrammed with multimedia graphics to animate thewearer’s physical posture, which is lying, sitting or walking.

An RS232 link is good while the subject is stationary, orwhile he/she is near the host computer or base station,whereas, the wireless link provides an advantage of mobilityto the wearer. The RF link is set at 15.6 kbps and it issufficient to pass any one ECG channel, three-axis tilt oracceleration information along with oximetry data. The localhost must be equipped with the physical layer connectivity tothe remote server. The remote computer may contain adatabase manager to upload and store detailed medicalinformation. The e-jacket does not contain a large storagespace, in order to reduce the overall cost. The acquiredsignals may be stored in the local host’s mass storage system.Figure 4 shows a possible telemedicine network with anaffordable infrastructure.

B. Comfort Analysis

The circuit has been designed to be concealed in the fabricof the jacket and must be removed while washing. The sizeand location matters for a comfortable experience by thewearer. Comfort Rating Scale [2] measures wearable comfortin six dimensions, namely, emotion, attachment, harm,perceived change, movement and anxiety. Considering thesepoints in mind the hardware must be placed at a strategiclocation, such as in the left side front pocket of the woolenjacket. The temperature sensor and ECG electrodes arepassed out through the inner side hole of the pocket. Thewires and cables are kept thin so as to avoid inconvenience

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TABLE ISPECIFICATIONS

Bio-parameter Sensor Feature BandwidthSampling

RateInterface

with MCUSupplyCurrent

Electrocardiogram Conductingelectrodes andgel based straps

Ch 1 [LI, LII, LIII]

Ch 2 [aVL, aVR , aVF, LII]Ch 3 [V (V1 - V6)]

0.05Hz to 106 Hz 256sps Analog 2.65mA

Pulse Oximetry PPG probe �R= 650nm, �IR= 850nm, 0.5Hz to 5Hz 40sps Analog 15 mA, 33 mATilt/ Acceleration Accelerometer

IC (MMA7260)3 axes 0Hz to 40Hz 100sps Analog 0.5 mA

Skin Temperature Temp. SensorIC (LM92)

Accuracy = ±0.33 degreeCelsius

---- 1sps Digital (I2C) 0.6 mA

Figure 5. Acquired waveforms using e-jacket.

TEMPERATURE Vs TIME

due to unnecessary body contact. As shown in figure 1b thewires for the temperature sensor is stitched inside the liningof the jacket. The ECG electrodes are kept short.Lightweight and thin shielded cables with micro miniatureconnector are utilized.

The oximeter probe comes out from the front side of thepocket and may be kept inside while not in use.

V. RESULT

The presented jacket targets tropical climate dwellers,therefore industrial grade components have been used in thesystem. The physiological waveforms from the e-jacket areshown in figure 5. Sample ECG signals for lead I, aVL andV5 are shown. The limb lead LI and augmented lead aVL arethe frontal plane measurement and V5 is a V-lead intransverse plane. In all cases, the low amplitude P-wave isvisible in addition to QRS complex and T-wave.

The accelerometer data is shown in a group ofsimultaneously acquired three axes of x, y and z, at threedifferent physical postures. PPG waveform for red andinfrared response is also shown in the same figure. Areasonably good quality in measured waveforms is achieved.A little 50Hz noise is seen riding over the signals, and maybe corrected using digital filters and shielding. The data issufficiently reliable for medical monitoring purposes. Aspecification chart is shown in Table I.

The wireless link works seamlessly in the jacket. This willaid in motion artifact related studies for ambulatory subjects,in addition to convenience during measurements.

Power-performance optimization [3] technique isimportant in wearable computers and has been achievedthrough iterative designs and intelligent processingtechniques. The patient specific calibration and tuning of thesensors is possible only in software [4]. A basicdemonstration of the smart garment in a telemedical scenariohas been demonstrated through this research.

VI. FUTURE WORK

The e-jacket has room for enhancement. Bioparameterssuch as blood pressure, respiration, EMG will be added inthe future versions. Micro SD card based storage facilitymay be added and thus the system will be ready for longduration recordings, such as with field workers. Removal ofmotion artifact is important to enhance the usability in

challenging conditions. The standard RF communicationprotocols such as Bluetooth or Zigbee may replace theexisting wireless connectivity with increased softwareoverhead.

Incorporation of real time (RT) Linux based operatingsystem architecture in the e-jacket will move a step ahead in

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complicated task management. On board TCP/IP stack willaid stand-alone solution for remote data link. Intensivehospital trials are required. The jacket must satisfy IECspecifications for patient safety and reliability.

ACKNOWLEDGMENT

The authors would like to thank Ashrut Ambastha,Maryam Shojaei Baghini, Shameek Bose for usefuldiscussions, and Sohrab Wadia for providing the graphicaluser interface.

REFERENCES

[1]. Yong-sheng Yan, Carmen CY Poon and Yuan-ting Zhang, “Reductionof motion artifact in pulse oximetry by smoothed pseudo Wigner-Ville distribution”, Journal of NeuroEngineering and Rehabilitation,2005, 2:3 doi:10.1186/1743-0003-2-3.

[2]. Knight, J.F.; Baber, C.; Schwirtz, A.; Bristow, H.W., “The comfortassessment of wearable computers”, International Symposium onWearable Computers, 2002. (ISWC2002), Proceedings, Sixth 7-10Oct. 2002 Page(s):65 – 72.

[3]. Smailagic, A.; Siewiorek, D.P.; Ettus, M., “System design of low-energy wearable computers with wireless networking”, Proceedings,IEEE Computer Society Workshop on VLSI, 19-20 April 2001Page(s):25 – 29.

[4]. Emil Jovanov, Aleksandar Milenkovic, Chris Otto and Piet C deGroen, “A wireless body area network of intelligent motion sensorsfor computer assisted physical rehabilitation”, Journal ofNeuroEngineering and Rehabilitation, 2005, 2:6 doi:10.1186/1743-0003-2-6.

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