Biological Optical-to-Chemical Signal Conversion Interface: A Small-scale Modulator for Molecular Communications

TL;DR

This paper introduces a biological microscale modulator that converts optical signals into chemical signals using engineered bacteria, enabling molecular communication at microscale with potential applications in bioengineering.

Contribution

The work presents a novel biological interface that translates optical signals into chemical signals via bacteria, demonstrating a functional microscale modulator for molecular communications.

Findings

Successfully converts optical signals to chemical signals at 1 bit/min

Developed an analytical model linking optical input to pH change

Validated the system with experimental data and pH sensing

Abstract

Although many exciting applications of molecular communication (MC) systems are envisioned to be at microscale, the available MC testbeds reported in the literature so far are mostly at macroscale. This may partially be due to the fact that controlling an MC system at microscale is quite challenging. To link the macroworld to the microworld, we propose a biological signal conversion interface that can also be seen as a microscale modulator. This interface translates an optical signal, which can be easily controlled using a light-emitting diode (LED), into a chemical signal by changing the pH of the environment. The modulator is realized using \textit{Escherichia coli} bacteria that express the light-driven proton pump gloeorhodopsin from \textit{Gloeobacter violaceus}. Upon inducing external light stimuli, these bacteria can locally change their surrounding pH level by exporting protons into the environment. Based on measurement data from a testbed, we develop an analytical model for the induced chemical signal as a function of the applied optical signal. Finally, using a pH sensor as detector, we show for an example scenario that the proposed setup is able to successfully convert an optical signal representing a sequence of binary symbols into a chemical signal with a bit rate of $1$~bit/min.