# Further Reading > We demonstrate a low-cost battery-free rapidly deployable and disposable patch for electrophysiological monitoring. This was performed by printing a stretchable AgInGa circuit over a temporary tattoo paper that is then transferred to a volunteer’s chest. The disposable patch BOM cost is less than 1$US, and can be rapidly customized with the presented printing technique. We showed that the electrodes printed with this method provide low skin-electrode impedance and excellent signal to noise ratio. The patch is then interfaced with a battery-free circuit for data acquisition, processing and communication via Bluetooth (Alberto et al., 2020). Alberto, J., Leal, C., Fernandes, C. *et al.* (2020). Fully Untethered Battery-free Biomonitoring Electronic Tattoo with Wireless Energy Harvesting. *Sci Rep* *10*\*\*,\*\* 5539. > Historically this has been a large and bulky technology, restricted to the monitoring of subjects in a lab or clinic while they are stationary. Over the last decade much research effort has been put into the creation of “wearable EEG” which overcomes these limitations and allows the long term non-invasive recording of brain signals while people are out of the lab and moving about. Casson A. J. (2019). Wearable EEG and beyond. *Biomedical engineering letters*, *9*(1), 53–71. > Researchers at Graz University of Technology in Styria, Austria have come up with a more subtle, user-friendly device for measuring brain activity: wafer-thin "tattoo" electrodes that are barely detectable on the skin (Linder, 2020). Linder, C. (2020). Electrode Tattoo Can Record Your Brain Waves, Make You Feel Like a Cyborg. Popular Mechanics \[online]. Available at: --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.lynx.phas3.io/further-information/further-reading.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.