Manufacturing Processes of Electrochemical Strips

Manufacturing Processes of Electrochemical Strips

A glucose test strip is a thin stack of layers. At the bottom sits an electrode layer, above it an adhesive spacer, and on top a hydrophilic (water-attracting) cover [1]. Strip makers pattern the electrodes in one of two main ways. Screen Printing pushes conductive ink, usually carbon-based, through a patterned mesh, while Laser Ablation starts with a thin metal film such as gold and uses a laser to cut away everything that isn't electrode [2]. Screen printing is what brought the cost of each strip down; laser ablation is used where a maker wants tight control over electrode dimensions [3]. The sources we checked don't say which method a given brand uses, so we don't pair either one with a company here. For a side-by-side look, see our article on screen-printing vs. laser ablation manufacturing.

Key Production Stages

Most strips pass through four stages, though each manufacturer runs its own version of the line.

• Electrode Patterning: The electrodes are formed on a plastic base such as PET (polyethylene terephthalate). Printing and cutting low-cost plastics and conductive pastes is how disposable strips are made at large scale [1].
• Reagent Deposition: An enzyme and an electron mediator are applied over the working electrode. The enzyme is glucose oxidase (GOx) or a glucose dehydrogenase (GDH) [1][3]. The mediator, a chemical such as ferricyanide, carries electrons from the glucose reaction to the electrode [1].
• Capillary Assembly: The adhesive spacer and the hydrophilic cover go on top. The spacer layer forms the tiny chamber, really a miniature electrochemical cell, that the blood sample fills [1].
• Calibration: During manufacturing, makers set calibration factors for the strip reagents, often by checking them against a laboratory glucose analyzer [4]. Some meters then ask the user to enter a code tied to the strip lot. Here's what surprised us: in a study the review describes, some miscoded meter and strip combinations put more than 90% of results in error-grid zones that would lead to a different clinical action, while meters with automatic calibration or No Coding didn't show those errors [4]. For more on how coding changed, see our article on the evolution of calibration coding.

Industry Shift

Strips have shrunk a lot. Over the decades, the blood needed for one test fell from 25 µL to as little as 0.3 µL, and the wait dropped from about 2 minutes to about 5 seconds [3]. Thin-Film metal electrodes patterned by laser ablation are part of that story, because they let makers control electrode size precisely [3]. What we couldn't confirm is the bigger claim: we found no source showing that the industry as a whole has moved to thin-film metals, or crediting the smaller samples to that switch alone. Screen printing is still described as the way to mass-produce strips at low cost [1].

Whichever method a maker picks, the finished system has to be accurate. ISO 15197:2013, the international standard for home blood glucose monitoring systems, requires 95% of results to fall within ±15 mg/dL below 100 mg/dL, or within ±15% at 100 mg/dL and above [3]. That depends on the whole system, including how the meter is calibrated and coded, and not only on how the electrodes were made [4].