Glasmembranet

Glasmembranet refers to a thin layer of glass that forms a barrier or functional interface in a range of technical devices. It can be dense and nonporous, serving as a protective or barrier surface, or porous, functioning as a membrane that allows selective transport of liquids or ions. In Swedish technical usage, glasmembranet is closely associated with the glass membrane of pH sensors and other ion-selective electrodes.

Composition and structure: Most glasmembranes are made from silica-based glasses, such as borosilicate or soda-lime compositions. Nonporous glass membranes rely on surface chemistry for ion exchange and signal generation, while porous glass membranes contain a network of pores that enable filtration or selective diffusion. The pore size and surface properties determine the selectivity and flow characteristics.

Fabrication and processing: Manufacturing includes forming thin glass sheets or coatings on supports, thinning and polishing to the desired thickness, and, for porous versions, methods such as phase separation or etching to create pore networks. Glass membranes can be integrated with microfluidic chips, electrodes, or solid supports through bonding techniques to form stable, functional interfaces.

Properties and limitations: Glass membranes offer high chemical and thermal stability, optical transparency, and good mechanical strength, but they can be brittle and susceptible to fracture. In sensing applications, performance depends on surface composition, thickness, and aging effects such as ion exchange or leaching, which can cause drift over time.

Applications: The primary use is in pH measurement, where the glass membrane forms the sensing interface of pH electrodes. They are also employed in ion-selective membranes, microfluidic devices, filtration systems, and protective layers for various sensors.

History: The concept emerged with the development of the pH glass electrode in the early 20th century, with ongoing advancements expanding the role of glass membranes in analytical chemistry and microfabrication.