Transepithelial/endothelial resistance (TER) measurement is a non-invasive method to assess the integrity of tight junctions in model cells such as the intestinal epithelium and the blood-brain barrier. This technique is essential for experiments on drug kinetics and tissue damage, but commercial devices have many limitations. Additionally, the high-grade analyzers for long-term measurements are prohibitively expensive, raising barriers to entry into this research field. 
The open source-based experimental equipment has advantages such as cost reduction and high versatility. There have been reports of TER instruments using 'open-source way' methods, but some of these have reproducibility problems. 
We propose OpTER, a reproducible, and inexpensive TER measurement method. An Arduino-based measuring circuit can be created for less than 10,000 yen. Our method enables the recording of results equivalent to those of a commercially available product. Along with homemade electrodes made of biocompatible metals, this enables continuous measurement of TER in an incubator.
The circuits and program will be available, and its simple mechanism, which can be assembled by non-experts in electrical engineering, can easily be modified to suit the researcher's objectives. This idea is a new 'OpTion' for both amateurs and professionals.