1. Flexible Sodium Ion
Selective Electrodes for
Biological Application
By
Shan Jafri

2. Objective
 Developed means to generate large scale arrays of
silicon micro-electrodes from bulk wafers
 Tested the sensitivity of ion selective electrodes (ISE)
for targeted ions.

3. Technical Approach
 For biological application, soft and stretchable
platforms were used to offer high degrees of
mechanical flexibility.
 For a higher concentration gradient, a larger electrode
spatial layout was used.

4. Technical Accomplishments
• 150nm thin gold plated electrodes from bulk silicon
wafers were created with an electron beam deposition.
• An array of thin micro-electrodes were fabricated
followed by transfer printing on silicone surfaces.
tape
stamp
Source
wafer
Pick and
place
microelectrodes Receiving stretchable
substrate

5. Technical Accomplishment
 A spin coater distributed even surface of
polydimethylsiloxane(PDMS) and photoresist.
 A mask aligning created complex patterns on gold
coated silicon wafers.

6. Technical Accomplishment
 The change in potential was measured after each
successive increase in Na+ concentration.

7. Represented Results
 The ISE were designed for Na+ as the target ion and
sensitivity of the ISE was tested with K+, a non-
targeting ion.
 100μL of 1M NaCl was added four times, consecutively,
in 1L of standard solution. Next, 100μL of 1M of KCl
was added three times consecutively.

8. Represented Results
Slope = 0.0542V/M
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0
Avg.ChangeVoltage(V)
Log[Na+] (M)
NaCL Sensitivity

9. Represented Results
Slope = 0.0163V/M
0.0575
0.058
0.0585
0.059
0.0595
0.06
0.0605
0.061
-2.32 -2.3 -2.28 -2.26 -2.24 -2.22 -2.2 -2.18 -2.16 -2.14
Avg.ChangeVoltage(V)
Log(K+) (M)
KCl Sensitivity

10. Conclusion
 The results showed that ISE could detected Na+ ions at
low concentration however, when K+ was present there
was some interference in the potential.