Electronic (bio)sensors using FET as the transducer

Part One is about FET fundamentals, different types of FETs, and how to use the EmStat Pico to characterize them.

Part two is more focused on advanced FETs, for example, graphene as the semiconductor, the concepts of organic electrochemical FETs, etc.

Field Effect Transistors (FET) are common electronic components, but they are also suitable to build chemical (bio)sensors with in-built signal amplification. Electrochemists are hesitant to explore the possibilities of FET-based sensors, due to the hurdle of investment costs for characterization tools. This webinar aims to change that.

Two Presenters:
Dr. Lutz Stratmann (PalmSens) will discuss with FET expert Dr. Marcin Szymon Filipiak (Institute of Physical Chemistry, Polish Academy of Sciences) the basic principles of FET-based sensors, how they are characterized, what instruments to use, and some application examples.

EmStat Pico Dev Kit App note - FET Characterization

Chapters in video: quickly jump to your favorite topic

Chapters in webinar Electronic (bio)sensors using FET as the transducer – part 1

  • 0:00 Introduction of speakers
  • 2:00 Bipotentiostat to measure FETs
  • 5:05 Cooperation for validation with Institute of physical chemistry
  • 6:20 Introduction Marcin Szymon Filipiak
  • 9:06 What are Field-effect transistors?
  • 11:36 Two approaches to connect bipotentiostat to FET
  • 15:00 Benchmarking of EmStat Pico
  • 17:18 Three architectures for biosensing application
  • 20:47 Extended-gate measurements with EmStat Pico
  • 29:14 Advantage and challenge for FET-based biosensing
  • 32:43 Receptor size in immunoFETs, surface engineering and PEG
  • 40:50 Example measurement TSH spiked horse serum
  • 44:10 Conclusion
  • 47:18 Question 1: Is it possible to measure transconductance, using EIS with a PalmSens potentiostat?
  • 48:30 Question 2: What is PEG’s role? What is the sensing mechanism? Are you sensing the analyte’s charge?
  • 48:38 Question 3: Does 10nA make sense in bio-wearables in reality?
  • 51:21 Question 4:
  • 51:20 Can I use the PalmSens4 for measuring using FETs?
  • 54:10 Question 5: How to connect a bipotentiostat to a FET?
  • 57:12 Question 6: Why is the counter and reference electrode connected to each other?
  • 58:55 Question 7: Can the EmStat Pico measure all three types of FET architectures for biosensing?
  • 1:03:46 Question 8: How does PEG spacer enhance sensitivity and may it also contribute some charges?
  • 1:05:58 Question 9: What are the crucial parameters when choosing your FET for a biosensor application?


Chapters in webinar Electronic (bio)sensors using FET as the transducer – part 2

  • 0:00 Introduction of the speakers
  • 0:30 Summary Electronic biosensors using Field-effect transistor as the transducer – part 1
  • 3:20 Introduction Marcin Szymon Filipiak
  • 4:55 Chapter 1 – Miniaturized multiplexed bipotentiostat for field-effect transistor based biosensing
  • 5:06 Chapter 1 – Proof-of-concepts studies using EmStat Pico MUX16
  • 16:20 Chapter 1 – Conclusion
  • 16:52 Chapter 2 – Single-sheet CVD grown graphene
  • 20:40 Chapter 2 – MOSFET vs Electrolyte-gate FET
  • 21:50 Chapter 2 – GFET measurement setup using the EmStat Pico Development Kit
  • 28:02 Chapter 2 – Conclusion
  • 29:05 Chapter 3 – Organic Electrochemical Transistor (OECT)
  • 31:30 Chapter 3 – conclusions
  • 34:35 Question 1 – Is the gate the gold electrode, and is it grounded as well?
  • 35:23 Question 2 – What is the thickness of the gold layer?
  • 36:00 Question 3 – What is the noise on the end of the graph?
  • 37:57 Question 4 – Why are you putting the FETs in a Faraday cage while it appears you have long and unshielded cables?
  • 40:46 Question 5 – Why do 16 MOSFETS of the same type show 16 different results?
  • 42:43 Question 6 – Is the GFET stable of time? Or is the leackage current increasing in time?
  • 45:22 Question 7 – Why do you need as many as 16 transistors for multiplexing? Wouldn’t just one transistor suffice?
  • 48:03 Question 8 – What is the difference between the EmStat Pico Development Kit and the EmStat Pico MUX16?
  • 50:19 Question 9 – What is the thiol chemical that you are using and what is the chain length?
  • 51:10 Question 10 – Why not use Carbon Nanotubes FETs that have a higher on/off ratio then FET?

Frequently asked Questions about FET measurements

Which instrument do I need for FET characterization?

For FET characterization two different potentials are controlled, VSD and VG, the source-drain current ISD is recorded, and optionally the gate current IG is recorded. A single-channel potentiostat won’t be able to perform these measurements. A bipotentiostat, two single-channel potentiostats or a multi-channel instrument are required.

Instrument needed for FET characterization

A bipotentiostat, two single-channel potentiostats or a multi-channel instrument are required.

An EmStat Pico has 2 WEs, 2 RE, and 2 CE connections because it has 2 channels. When switched to the bipotentiostat mode it has effectively 2 WEs, 1 RE, and 1 CE. The first WE can be used to control a variable potential and the second WE for applying a constant potential, while both electrodes record at the same time currents.

Using a single device with perfect synchronized potential control and current recording for the measurement is practical and cost-effective. An advantage of the EmStat Pico is the MethodSCRIPT capability. It allows effectively to have auto-ranging on both working electrodes. Standard bipotentiostat measurements allow the current range at the first WE to be optimized (auto-ranging), but the current range at the second WE is fixed. The MethodSCRIPT code for this application note (see Annex 4.1) includes a loop that optimizes the current range for the second WE, too.

Start with the EmStat Pico Dev Kit

Can I use PalmSens4 for this experiment?

Yes, the PalmSens4 Bipotentiostat is capable of performing these experiments, but there will be no auto-ranging for the second working electrodes. A good way to overcome this limitation is to split of the sweep in multiple measurements. This is conveniently done in PSTrace’s scripting window.

Discover the PalmSens4 with Bipotentiostat

Why did you combine CE1 and RE1 on the EmStat Pico?

We just need to control the potential as in a 2-electrode system. We don’t need the 3-electrode system. Therefore we combine CE1 and RE1.

More about 2- and 3-electrode systems

How is the WE1 potential is manipulated without reference RE1?

The EmStat Pico is used as a bipotentiostat instead of two separate channels. This means the WE0 and WE1 share both the same RE and CE.

More about Bipotentiostats

How does MethodSCRIPT work?

MethodSCRIPT is the language the latest generation of PalmSens potentiostats speak. MethodSCRIPT gives you full control over the instrument or potentiostat module. MethodSCRIPT allows you to customize and combine measurement techniques and perform actions including using on-board storage, data analysis and controlling external peripherals. The EmStat Pico for example, supports MethodSCRIPT.

Use MethodSCRIPT on the EmStat Pico Dev Kit

Read the app note - FET Characterization

Read more about MethodSCRIPT



Is the code shown to perform FET measurements available?

Yes, the code is described in the corresponding application note and available as download in the Knowledge Base, together with the app note on how to use the code:

MethodSCRIPT to perform FET measurements

Read the app note - FET Characterization

Hoe does the PGE spacer helps to improve the sensitivity?

PEG – Polyethylene glycol is bio-repulsive and reduces the amount of unspecific adsorption.

How does a partnership with PalmSens works, given a FET biosensor platform is provided by a partner?

PalmSens does not provide contract research. PalmSens would be the supplier of the instruments and you would characterize your FET biosensor platform.

Can you keep source-drain current constant and measure the drain-voltage change during a gate sweep?

Keeping the source-drain current constant is used often for graphene FETs. The EmStat Pico is not a galvanostat, so at the moment, this isn’t possible. The PalmSens4 is capable of keeping the current constant.

Discover the PalmSens4 with Bipotentiostat

Does an extended gate FET based sensor amplify the signal in the same way as an on-board FET of the potentiostat used in the potentiostatic mode?

Question continues: Thus, wouldn’t it be safer/more reliable to rely on the onboard FETs or even add an extra onboard FET for signal amplification if needed?

Answer: The principles should be the same. The advantage of choosing your own FET is that you can choose the parameters that match your measurement principle and probe best. Extended Gate FETs are a good example to demonstrate the operation principle of other chemical FET types (ISFET, GFET), so for educational purposes, it is the best choice.