2. Abstract
1. Overview of Philips and Philips Research
2. Project aims and objectives
3. Methodology and experimental procedures
4. Results and Discussion
5. Personal experiences
3. Company Overview
• Koninklijke Philips N. V. = Royal Philips
• Dutch technology company focused on electronics
• Founded in 1891 by Gerard and Frederik Philips
• 1892: First introduced carbon-filament lamps in their 1st
factory in Eindhoven
• 1918: Introduced medical X-ray tube
• Present: Focus on Healthcare, Consumer Lifestyle and
Lighting
Philips Headquarters, Amsterdam, The Netherlands
4. Philips Research
Philips Research Headquarters, HTC, Eindhoven, The
Netherlands
• Located in the High Tech Campus, Eindhoven
• 1998: Philips HTC for all international R&D
activities
• 2003: Opened the campus to other tech companies
• 2012: Philips sold HTC to Ramphastos
Investments
• Smartest square km in The Netherlands
5. Philips Logo
• Stars: Sparks of innovation
• Waves: Radio waves and how the company has
digitally connected lives
• Circle: Lives of people touched around the
world
6. My Department & Project Motivation
• “Smart Interfaces and Modules” department
• “Emotion Measurement Platform for Daily Life Situations” project
• Purpose: Link psychophysiological measures to an emotional state by unobtrusive sensing
methods in a daily life setting – insight on the user’s tension patterns
• Main markets: Consumer Lifestyle and Healthcare
7. Project Scope
• Discreet Tension Indicator (DTI)
• Novel wireless multi sensor bracelet – measures skin conductance
(SC) in µSiemens
• Features an embedded assessment of the measured SC – detects
episodes of high arousal and signals this to the user
• Consists of 2 SC electrodes (minimum) - dry electrodes
• Wristband – non-permeable to gas/liquid – allows a microclimate
of sweat to exist
8. Research Purpose
Study the electrochemical stability of SC electrodes (metal &
polymer) by conducting laboratory experiments to:
• Understand their current carrying capacity
• Analyse current-voltage (I-V) characteristics
• Identify changes in pH and possible leachate products
9. Main Hypothesis
1. SC electrodes in current DTI:
Platinum-coated brass electrodes
• Possibility of Zn2+ ions from the brass electrodes to
leach out through Pt thin film – causes sweat
microclimate to become more basic from formation
of Zn(OH)2
• May cause skin irritations to the user
10. Main Hypothesis
Elements Copper Zinc Lead Titanium Platinum
Ions Cu2+ Zn2+ Pb2+ Ti4+ Pt+
Ionic Radius/
Angstrom (Å)
0.73 0.74 1.19 0.605 0.625
11. Main Hypothesis
2. Biocompatible hydrophilic conductive silicone
• New innovation to replace metal electrodes –
improve user comfort
• Addition of soap beads – Sodium xylenesulphonate
(SXS) – gives hydrophilic nature BUT may decrease
the acidity of the sweat microclimate
• May cause skin irritations to the user
12. Experimental Methods
1. Cyclic Voltammetry (CV)
• A fixed potential range is selected – voltage is scanned from lower to upper
limit – reaches upper limit, scan is reversed and voltage is swept back to the
lower limit.
• Obtain I-V characteristic curves – shows relationship between the current
flowing through the electrodes (metal & polymer) and the applied voltage
across its terminals.
15. CV Experiments
For this study:
• All working electrodes are characterised in-vitro in dilute HCl acid solutions
through CV using LabVIEW
• Test solution: approx. 4.5-pH ≈ human eccrine sweat
• Test conditions: -3V – 3V potential window with 10mV step size
• 30 cycles of CV – approx. 7.5 hours of electrode use
16. Mass of Reacted Ions
Determine a means of calculating the mass of Pt-ions involved in the
electrochemical reaction using LabVIEW:
1. Take current on the rising/declining cycle and multiply by step time to
obtain amount of charge (C)
2. Divide charge value by Faraday’s constant (96485.3 C mol-1) to obtain
rising/declining moles of Pt-ions
3. Multiply moles of Pt-ions with its molecular mass (195.084 g/mol) to
obtain actual mass of Pt-ions involved
17. Results & Discussion
General observations:
• Shape of curves were relatively similar
throughout the 30 cycles
• The peaks of the curves gradually increased
as no. of cycles increased - electrodes
experiencing higher activation – decreasing
resistance
• Less hysteresis of the curves as no. of
cycles increased – electrode becoming stable
18. CV Results
• Drop in current carrying capacity
from 11th to 12th cycle (yellow to
black)
• Peak current remained the same
• Drop corresponds to the pH change
in the next figure
19. pH Results
• Drop in current carrying capacity and
pH increase – due to slight
evaporation of test solution overnight
• Maybe temperature changes in gas
chamber led to this
• 11th to 30th cycle - +0.3-pH change in
50mL of test solution
20. pH Results
The pH change can be translated with a scale factor to represent the pH change
in the actual sweat climate:
1. Total area of (2) SC electrodes = 0.0002 m2
2. Separation of sweat from electrodes (hair/skin contour) = 250 µm
3. 1 Litre = 0.001 m3
4. Approx. volume of actual sweat climate = 0.0002 * 0.00025 * 1000 = 50 µL
21. pH Results
5. pH = - log10[H+]
6. This 0.3-pH change in 50 ml test solution translates to 3-pH change in
50µL of sweat due to a scale factor of 1000 from the equation in 5.
Therefore, the actual approx. increase in pH for 50 µL of sweat would be from
4.5 to 7.5.
22. Mass of Reacted Ions
• Mass of Pt-ions during upward cycle –
relatively steady throughout CV –
average of 14.5µg
• Drop in mass from 11th to 12th cycle
relates to drop in current carrying
capacity and pH increase
23. Mass of Reacted Ions
An approximation of the % loss of Pt from the electrode during the electrochemical
reaction after 30 cycles of CV can be calculated:
1. Thickness of sputtered Pt layer ≈ 4 µm
2. Total mass of sputtered Pt layer
= area*thickness*specific weight of Pt
= 1 cm2 * 4 µm * 21.4 g/cm3 =8.56 mg of Pt
3. % loss of Pt = (14.5µg/8.56mg)* 100 = 0.17% Pt loss after 7.5 hours CV
Therefore, it would take about 184 days for the Pt layer to disappear.
24. Conclusion & Recommendations
Conclusion:
Limited results, no CV in artificial sweat and unproven implications but methods and
results deemed appropriate for future research
Recommendations:
• Use thermostated cell and vacuum chamber for electrode setup and CV
• Conduct electrode experiments with artificial sweat followed by human testing
• Longer durations of CV for life-cycle analysis of electrodes
SXS – hydrotropes – increase the ability of water to dissolve other molecules – gives shampoo the gel like feel
Explain like after initial experimentation you came up with final parameters
Limited labview knowledge – programs created by supervisor martin ouwerkerk
