5.1 Application of screen printed electrode - electrochemical detection product design - Micro, single use, calibration-free pH electrode

With the rapid development of various detection technologies, it is exciting and challenging to develop new products to meet new requirement. We will introduce this micro ,disposable and calibration-free pH test electrode(humming probe) as an example to show “How to develop a electrochemical sensor? “. We invite UltraE founder ,B.C Hsieh, to share with us about every stage of electrochemical product design which including research on market demand and competitors, design protoype from conception, how to highlight the unique of products and expanding the field of application.

• 5.1.1 How to establish the design specification of new electrochemical detection products？ Three steps: Discover, invent and perform

  Discover stage: demand discovery, market research, demand screening

  The key themes of the discovery stage include both exploring and screening requirements. By observing and collect a large number of unmet test need and according to various application scenarios, business model and market characteristics and other information, we will select and propose a few feasible and promising program .
  
  Based on the functionality design of humming probe pH sensor, pH measurements were often used pH electrode when preparing buffer soltution , controlling synthesis process or sample pretreatment in our previous work in the laboratory. The traditional glass electrode is most commonly used in the laboratory. But there are many instructions needing attention in the use of glass electrode.

  
  


• User pain points：
  

  When using traditional glass pH electrode, firstly you need to remove the glass electrode from the storage solution (saturated KCl solution), check whether there is crack , bubbles on the surface or in the electrode. If everything is OK for appearance, we should use distilled water or the sample liquid to rinse the salt off from the electrode surface, blot dry and ready for use. Every week or when precise testing is required, we need to purchase the standard solution to calibration system with two or three points according to the instructions before starting the experiment. In addition to these calibration steps, it is also necessary to pay attention to whether the plug on the glass electrode is opened, or whether the temperature inside the electrode is consistent with the sample temperature when measuring the sample higher or lower than room temperature. Usually, the pH glass electrode is shared in a lab. When some newcomers without fully training operate pH analyzer not correctly,or using the glass electrode to measure some samples which will contaminate electrode surface (such as some oily, protein or lipid samples). These incorrect operations will result in the pH glass electrode can not get accurate measurement. In this case, it should takes some effort and time to clean or fix it and sometimes it has to buy a new one. The worst thing is to use the pH glass electrode without knowing it has deviation, it will cause many problems in the subsequent research work.

  • 1 Frequent calibaration is required, and many consumables and time are needed for calibation.
  • 2.The electrode needs to be properly stored and mantained , otherwise it will affect the accuracy and precision of pH test.
  • 3.The electrode will be contaminated or difficult to clean after measuring some samples.
  


Research on competitive product:


According to the above, our product prototype design are start from these disadvantages of glass pH electrode and the pain points of users. At the beginning of the product concept, we do an extensive screening of the entire market need, which we call demand discovery. pH value measurement includes colorimetric method (pH test paper and cuvette) and potential method. Colorimetric methods are the simplest but do not provide a precise measurement. The core theory of potentiometry is Nernst equation which can obtain accurate and reproducible pH values. There are a variety of pH electrodes on the market (e.g. glass electrode, plastic electrode, planar electrode, solid electrode, etc.), each of which has its own applicable sample and pH range. So it would be a good idea to have an electrode that could be suitable to as many condition and requirements as possible.

pH Electrode / Available Application	Routine glass electrode	Solid / polymer filled electrode	Micro electrode	Surface electrode	Single use electrode	Low membrance resistance electrode	Humming Probe
Almost All aqueous sample	✓	✓	✓	✓	✓	✓	✓
Water solution	✓	✓	✓	✓	✓	✓	✓
Strong alkaline sample	▲						✓
Polluted waste water		✓			✓		✓
Suitable for dye/soil/food,etc. (plastic shell to protect against electrode damage)		✓					✓
Contain suspended solids		✓					✓
Contain protein		✓					✓
Contain some organic substance	▲						✓
Designed for measurements in small tubes. like Eppendorf and NMR		✓					✓
Costly DNA sample			✓				✓
Suitable for high viscosity samples/Such as homey/jam/hair dye, etc							✓
Available for sterilization Suitable for biochemical laboratory					✓		▲
Small or flat samples(Sweat)			✓	✓			✓
Suitable for surface of Skin /Blood/Agar plate				✓			▲
Ion-weak-samples like pure water						✓	✓
Gas sample							✓




Our team began to think about if there has a pH electrode that could meet the needs of as many samples as possible, easy to maintain, and be able to achieve accurate and reliable measurements even for people without training.



5.1.2 Invent stage：original and unique product features

Product positioning:

In this stage, some specifications of "you have, I have" were established according to the market demand and users' pain points. However, to establish new products and brands in the business sea, it is necessary to have product features and unique specifications that can be recognized. Therefore, the humming bird probe products are positioned in the following three points:




• 1.Calibration-free
• 2. Available for micro samples
• 3.Single use design and maintenance-free



Product design:

According to such product positioning requirements, we have proposed many possible ways to achieve it. Accurate pH measurement is based on the electrochemical Nernst equation, so electrode design is core point. After trying many kinds of electrodes, we finally decided to use the screen-printed electrode as the basic architecture to achieve the feature positioning of our products. Screen printing electrode (Screen printed electrodes, SPE), the carbon or other conductive ink can be printed on the surface of polypropylene with the linewidth around 100 μm to several millimeters and the thickness around 10 μm. And it has been the greatest platform to the development of point of care sensors such as glucose sensor for diabetes care which is the biggest health care market in the globe. Moreover, the production cost of the screen-printed electrode is much lower than that of the complex glass electrode, so we designed to let the user use the pH electrode in a disposable way, which can solve the problem of electrode maintenance and electrode contamination.

Finally, how to solve the problem of calibration. The pH electrode needs to be frequent calibrated because the effective ion exchange area on the electrode surface would be changed due to blocked or scraped. Therefore, it is necessary to use standard solution to make two to three points of correction before the measurement. For the screen-printed electrode, as long as we can stabilize the production of low batch difference, high quality screen printed electrode, we can finish calibration step in the factory by finite sampling correction. Therefore ,the user does not need to purchase additional standard solution and spend time on calibration, take out our electrode and it can be directly used.



Finally, how to solve the problem of calibration. The pH electrode needs to be frequent calibrated because the effective ion exchange area on the electrode surface would be changed due to blocked or scraped. Therefore, it is necessary to use standard solution to make two to three points of correction before the measurement. For the screen-printed electrode, as long as we can stabilize the production of low batch difference, high quality screen printed electrode .Based on above we can finish calibration step in the factory by finite sampling correction. Therefore ,the user does not need to purchase additional standard solution and spend time on calibration, take out our electrode and it can be directly used.




Partners

There are many manufacturers of instrument and electrodes for electrochemical research all over the world. But each has its own characteristics, some will focus on the research laboratory development stage that will provide more advanced products. And some will focus on mass production contract manufacturing. We selected Zensor R&D to participate in our co-development discussion. Because it has rich experience in electrochemical product design. Zensor's team is composed of senior electrochemical research scholars and have rich industrial experience in biosensor product development filed. Therefore, Zensor gave us many opinions from the customized electrode design, electrode cost control and high quality electrode maximum production planning. Beside positioning of Hummingbird probes, they helped UltraE solve the core product development problems together, such as:

• - How to establish a cost-effective electrode architecture that can be mass-produced at a low cost and has good electrochemical performance？
• - How to mass produce electrodes with low batch difference? How to embed temperature sensing elements to achieve senior temperature compensation?
• - How to use screen printing technology to design a long life stable reference electrode (discarded salt-bridge electrode) for long time detection?
• - How to import automation to improve quality and control cost?

Thinking these problems at the beginning of product design will reduce a lot of time and cost in development process. A good partners will also can follow your growth, not only to provide professional advice, but also to provide software and hardware integration service to you with an one-stop service from concept design , prototype design, pilot production, scale-up producton.



5.1.3 Perform stage: Open a new business model to provide customized services for micro pH sensors

Because using high precision screen printing technology, we can make the disposable pH sensing element very small and can get the detection accuracy to 0.1pH. Therefore, we can provide customized service (OEM/ODM) of embedding pH sensor to customers’ system. So in addition to setting our own brand and we will also bring a new business model to the pH acid-alkali detection market. We can continuously provide the pH strip at low unit price to the user in or outside the web. Furthermore , We will become an execellent partner vender to provide high-quality customized services which depend on our patented technology.


Some picture are refer UlraE Co. website： www.ultraehp.com/EN/index.html