Electrochemical sensing at Acreo- electrochemistry and impedance

Anatol Krozer, Sensor Systems, Göteborg

Kista, Stockholm (Optical Fibers R&D, Nano, SiC) …Norrköping (Printed electronics)

Hudiksvall (Optical fibers, R&D and production)

Göteborg,Sensor Systems

Acreo, Sensor Systems - people involved

Lei Ye, Keichii Yoshimatsu, … - Applied Biochemistry, Lund UnivKristina Reimhult, Lu Sun, …

Cristina Rusu

Fredrik Ahrentorp

Jakob Blomgren

Christer Johansson

Kristina Fogel

Dag Ilver

Andrea Astalan

TorbjörnPettersson

Boris Stoev

John Rösvall

AK

Fluid response to variable voltage - global vs local

𝑉 (𝜔)𝐼 (𝜔)

=𝑍 (𝜔 )=𝑍 ′ (𝜔 )+𝑖 𝑍 ′ ′ (𝜔 )=|𝑍 (𝜔)|{𝑐𝑜𝑠 𝜃+𝑖𝑠𝑖𝑛𝜃 }

VAC

IAC

• Mobile ions/charged particles in a liquid act to screen away an external electric field → charge separation → charge pile up close to electrodes. At most ionic concentrations of interest the electric field, E, inside the liquid is ≈ 0 in equilibrium.

• Typical screening distances at ionic strengths of interest here are < µm. The ion excess at electrodes (the double layer) induces capacitances µF.

• Ionic current in a fluid, I, is given by:

– concentration, – effective ion charge and – ion mobility.• Variable external voltage → I response lags behind V due to size effects.

Contribution due to ionic/particle motion decreases with frequency.

𝐼 (𝜔)𝑉 (𝜔)

=𝑌 (𝜔 )=𝑌 ′ (𝜔 )+𝑌 ′ ′ (𝜔)

Local (at electrodes): artificial biofilm – self assembled pH sensitive peptide monolayer

𝑉 (𝜔)𝐼 (𝜔)

=𝑍 (𝜔 )=𝑍 ′ (𝜔 )+𝑖 𝑍 ′ ′ (𝜔 )=|𝑍 (𝜔)|{𝑐𝑜𝑠 𝜃+𝑖𝑠𝑖𝑛𝜃 }𝐼 (𝜔)𝑉 (𝜔)

=𝑌 (𝜔 )=𝑌 ′ (𝜔 )+𝑌 ′ ′ (𝜔)

Designed, pH sensitive, thiol terminated peptides well known adsorption properties on the gold surface dense and insulating monolayer is formedC linear = CKHEYKHEYKHEYKHEYKEHEHEHH (-COOH)E - Glutamic acid; C - Cystein; K - Lysine; H - Histidine; Y – Tyrosine

Peptide layer thickness < 50nm

• Thickness changes of few nm can be detected• Detection of small changes of ion concentration• Quantitative detection by data fitting

-7

2

11

20

2 4 6 8 10pH

Net

Cha

rge

0

5

10

15

20

Δε

(M-1

cm-1

)

Δε at 225nm in Fig 6.3 (a)

Calculated C linear net charge

(b)

pH response

Global: aging of lubricants for cutting tools at Volvo Skövde plant

Planparallel electrodes Planar coil

Adding lubrication oil

Lubricant

Two approaches: • plane electrodes: f < 1MHz• Planar coil: f 5MHz

Vinnova grant – water quality monitoring ”Sensation”

Local: Biofouling - capacitive detectionSimilar principle applies for planar electrodes facing each other (see previous slide), for the interdigitated finger configuration or for planar coils as shown here.

Planar electrodes: Sensing depth is of the order of electrode – electrode distance.

MIPMIPMIP

Passive polymer matrix

MIP

+Si wafer/glas

+ -

Buffer

MIPMIPMIP

Passive polymer matrix

MIP

Si wafer/glas

-+

Example: Milk handling - biofilm

Molecularly imprinted polymers on microelectrodes- Polymers with molecular ”memory”

”artificial antibodies”- Applicable mainly to molecules < kDa but

imprints of peptides, proteins and even microorganisms are under development

- Robust (shelf life – years)

• Toxins, eg., marine toxins or volatile mould products• Narcotics• Chemical warfare agents• Explosives• Peptides• Pharmaceutical waste• Tannins, coffeines• Sugars, (sorbitol, glucose)

0

100

200

ImZ

DL-propranolol

Atenolol

0

100

200

300

400

0 200 400 600

Re

Z

Concentration (µM)

0

100

200

ImZ

DL-propranolol

Atenolol

0

100

200

ImZ

DL-propranolol

Atenolol

0

100

200

300

400

0 200 400 600

Re

Z

Concentration (µM)

0

100

200

300

400

0 200 400 600

Re

Z

Concentration (µM)

AFM

170nm S-MIP in PET

2,4µm S-MIP particles in PET

SECURITY - Emergency Support System no: 217951

to PCWatersupply

Zephyr - measuring ion content and moisture of earth

Results compared with the commercially available sensor

Drawbacks (lack of electronics for field conditions)• measures only Impedance amplitude! Phase info is lost (but Kramers-Krönig relations

are often applicable)• Measures only at descrete number of frequencies (here at 2 frequencies)→ requires extensive calibrations & modelling

Electronics underway (see eg., http://sciospec.de/cms/home)

Similar results for fits with less datapoints

Grant ENV.2012.6.3-1: ZEPHYR no: 308313

Zephyr - Improved model for soil measurements

Grant ENV.2012.6.3-1: ZEPHYR no: 308313

Coil as an electric component

R

LC

Frequency

R0

f < f0 Inductor

f > f0

Capacitancef << f0 resistor

R= (R0 + 2p fL0’’)

• ’ and ’’ – in-phase and out-of-phase electric susceptibilities (polarisabilities) of the of the surrounding media

• is the coupling coefficient to the measured media (eddy currents)• Eddy currents (Garcia-Martin etal., Sensors (2011) vol. 11, pp. 2525-2565) → R f2; L f2

• Typical skin depth is 0.2 m at 1 MHz and resistivity of 0.5 m (urine or physiological buffers) → in practice full penetration at most geometries

• Impedance in liquids → substitute C by constant phase element, CPE

L=L0 (1+ ’)

𝑓 0

𝑄∝𝑅=(𝑅0+𝛿 𝑓

2 ) , 𝛿∝𝜎 ; 1𝑓 0❑2 ∝𝐿𝐶∝𝜀

Molecularly imprinted polymers - MIPs

Coils covered with a dense ML of imprinted & non-imprinted beads using mussel adhesive proteins as a ”glue” (patent pending)

Dose response – target: propranolol

Use of planar coils to follow the kinetics of chemical binding (patent pending)

Fit quality!

SECURITY - Emergency Support System no: 217951

Practical implementation – battery-powered autonomous system

Temperature stabilisation

SECURITY - Emergency Support System no: 217951

Fully automatised and energized Wheatstone bridge configurationto detect changes of abs(ZMIP) – abs(ZNIP)

MIP NIP

R1R2

Vac

+-

Anatol Krozer /20090121/

Film adhesion & MIP performance• Insufficient Au surface cleanness• Film stability• Poor sensitivity of impedance measurements →

Use Imego designed microelectrodes

Home-made electrochemical cell with an option for surface plasmon resonance detection

• Clean electrodes: H2O2/HNO3/H2O, UV-ozone & CV in 1M sulphuric acid

• Polymerisation in 10 mM acetate with monomer (54 ml 100 mg/ml) and 5 mM sorbitol• Deposit polymer by CV. Low current implies the formation of a continuous MIP film.

The effect of Au cleannesson MIP deposition

5 min

60 min

Monomer solution,Electropolymerisation delayed by:

0 0,1 0,2 0,3 0,40

0,05

0,10

0,15

Time (Hours)

Q [

Ase

c/cm

2 ]

Film preparation

MIP performance by electrochemical impedance

MIPdeposition

sorbitol20mM

wash

sorbitol5mM

wash

2nd MIPdeposition 3rd MIP

deposition

sorbitol5mM

wash(sonication) wash

washwash

Au

200

600

1000

|Z|

Molecular Imprinting of sugars (sorbitol)– cyclic voltammetry (CV)

Q [A

sec/

cm2]

MIP deterioration upon template cycling 1st

2nd

3rd

0 0,1 0,2 0,30

0,05

0,10

Time (Hours)

MIP deposition

0

0.001

0.002

0 0.2 0.4 0.6 0.8Voltage (V)

MIP deposition

0

0.001

0.002

0 0.2 0.4 0.6 0.8Voltage (V)

0

0.001

0.002

0 0.2 0.4 0.6 0.8Voltage (V)

MIP deposition

Integrated printed disposable biosensor – Acreo Printed Electronics

First demonstrator

Current status

Finalgoal

Printed battery

Chip

Printed circuitry

Printeddisplay

Printed biosensor

Demonstrated with glucose sensing

On-board signal processing

Amperometry, potentiometry or impedance

Acreo Printed Electronics – manufacturing greenhouse

• 500 m2

– 6 Printing machines screen, flexo, (2 R2R)– Equipment for test and inspection– Equipment for ink development – Offices– Meeting places

• Manufacturing processes– 5 R2R single component processes– 4 sheet integrated systems processes– 1 R2R integrated system process (under development)

• Activities– Prototype design– Product development – Production– Technology transfer– Workshops

Collaboration with the Linköping University

The end!

• Impedance is by far not the only area of our interest! Please contact me for further information about our other activities. These include: – MEMS and their signal analysis - MEMS systems– Magnetism & magnetic nanoparticles– Optical sensors – fluctuations, fluorescense, FRET, etc.

• We apply these to:– Inertial navigation– e-health and e-sports– Immunoassay platforms– Water quality monitoring (raw water, industrial waste, urban water systems, etc.)– Bacteria detection and living sensors– Agriculture and cattle

– You name it!• We aim at cheap but fully automatized systems• We gladly welcome industrial and academia cont(R)acts and collaborations,

and common funding applications!

Additional activities

Zephyr measuring ion and water content using wrapped coils

Grant ENV.2012.6.3-1: ZEPHYR no: 308313

• Both inductance and capacitance changes

• It is possible to extract conductivity ( ion content) and capacitance ( water content)

Urea in tap water

103

104

105

106

|Z|

10-1

100

101

102

103

104

105

106

-100

-50

0

Frequency (Hz)th

eta

MQ 2Tap water 1 Tap + 5% urea

Tap water 2MQ 3

0 2000 4000 6000 8000

-2000

-1000

0

Z'

Z''

0 2,5 5

-27

-2 x104

Requires Differential Impedance Analysis

Our collaborators in Bulgaria – differential impedance analysis

• Construction of a continuous, virtually care-free and self-calibrating equipment is possible

• Although we presented data only up to 1 MHz we do have experience with experiments up to few tens of GHz. The latter may allow

– remote sensing– ”chemical specificity”

• Use of several narrow frequency measurement intervalls decreases equipment cost and enhances specificity

• Software development and signal analysis are important

• Water-in-oil

• Oil ageing• Urea

Waste from the waste treatment plant at Borås

Beaker with sedimented waste (after 0,5h) and electrodes 0 10000

-28000

-18000

-8000

Z'

Z''102

103

104

|Z|

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

TS = 8,4% utspädningx0 x2 x4 x8

0 10000

-28000

-18000

-8000

Z'

Z''

0 10000

-28000

-18000

-8000

Z'

Z''102

103

104

|Z|

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

TS = 8,4% utspädningx0 x2 x4 x8

102

103

104

|Z|

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

TS = 8,4% utspädningx0 x2 x4 x8

102

103

104

|Z|

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

x8x8separation x0

homogen x0

102

103

104

|Z|

102

103

104

|Z|

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

100 102 104

-75

-50

-25

0

Frequency (Hz)

thet

a

x8x8separation x0

homogen x0 x8x8separation x0

homogen x0x8separation x0

homogen x0

Monitoring fluid level

Coil area: 50mm x 50mmMid open area: 10mm x 10mmPitch = line width = 0,2mm

• Probe depth ≈ width of the (pitch + current line)• Similar sensitivity for 3-dim coil and for coils wrapped around

the polymer chamber from the outside. • Resonance damping (quality, Q-factor, decrease) depends on

the ionic concentration. For naked coil wires and ionic strengths typical of urine Q is low, Q 1

• Damping decreases considerably when the coil is covered by thin but dense insulating layer

COILS

Planparallella elektroder

1

9

8

Två olika representationer av mätdata

Ny vätske”batch”

• Slutsatser: det går att mäta något större (?) skillnader mellan de olika skärvätskorna även för den nya batchen jämfört med skillnadetr vid högre frekvenser

• Modellering behövs

𝑍=𝑅

1+( 𝑗2𝜋 𝑓𝑅𝐶 )∝

0

20

40

60

80

100

105 107

Abs

(Z

) (O

hm)

f (Hz)

Value102R

3.1188e-8RC 0.99199 a

Conductivity ion content

200

400

600

800

Z'(O

hm @

10

kHz)

Capacitans water content

0

100

200

0 40 80 120Cap

acita

ns (

pF @

3M

Hz)

Water content (ml)