In this letter, we investigate diffusion-based molecular communication between two mobile nano-machines. We derive a closed-form expression for the first hitting time distribution by characterizing the motion of the information particles and the nano-machines via Brownian motion. We validate the derived expression through a particle-based simulation. For the information transfer we consider single particles of different types, where transposition errors are the dominant source of errors. We derive an analytical expression for the expected bit error probability and evaluate the error performance for the static and the mobile case by means of computer simulations.

In multi-cellular organisms, molecular signaling spans multiple distance scales and is essential to tissue structure and functionality. Molecular communications is increasingly researched and developed as a key subsystem in the Internet-of-Nano-Things paradigm. While short range microscopic diffusion communications is well understood, longer range channels can be inefficient and unreliable. Static and mobile relays have been proposed in both conventional wireless systems and molecular communication contexts. In this paper, our main contribution is to analyze the information delivery energy efficiency of bacteria mobile relays. We discover that these mobile relays offer superior energy efficiency compared with pure diffusion information transfer over long diffusion distances. This paper has widespread implications ranging from understanding biological processes to designing new efficient synthetic biology communication systems.

Motivated by the numerous healthcare applications of molecular communication within Internet of Bio-Nano Things (IoBNT) paradigm, this work addresses the problem of abnormality detection in a blood vessel using multiple biological embedded computing devices called cooperative biological nanomachines (CNs), and a common receiver called the fusion center (FC). Due to blood flow inside a vessel, each CN and the FC are assumed to be mobile. In this work, each CN performs abnormality detection with certain probabilities of detection and false alarm. The CNs report their local decisions to a FC over a diffusion-advection blood flow channel using different types of molecules in the presence of inter-symbol interference, multi-source interference, and counting errors. The FC employs the OR and AND logic based fusion rules to make the final decision after decoding the local decisions using the sub-optimal detectors based on the approximation of the log-likelihood ratio. For the aforementioned system, probabilities of detection and false alarm at the FC are derived. Finally, simulation results are presented to validate the derived analytical results, which provide important insights.

In this work, we present a novel portable, flexible and easy-to-use experimental setup for investigating salinity-based information transmission in microfluidic channels. At the receiver, the different salinity-levels are detected by a customized electronic circuit, which measures electrical conductivity via electrodes in the microfluidic channel. We provide a detailed description of the setup, including the microfluidic chip fabrication. Moreover, we develop a rigorous mathematical model of each testbed component and an end-to-end model of the system, which we have verified through experiments. Finally, we analyzed the error performance of the setup using optimum and sub-optimum detection algorithms, such as the Viterbi algorithm and threshold detection.

The paper presents the significance of microfluidic technology in advancing Molecular Communications (MC). It highlights the transition from theoretical MC models to practical applications, emphasizing the role of microfluidics in validating and advancing MC concepts. The paper covers various aspects including theoretical principles, simulation tools, practical realizations, and envisioned applications. We also present various microfluidic testbeds, detailing their design, capabilities, and applications in advancing MC. To bridge the gap between theoretical models and practical outcomes in MC, this work demonstrates the potential of microfluidics in the practical realization of MC systems.

This work investigates the problem of flow-induced diffusive molecular communication under various mobility conditions such as (i) both transmitter (TX) and receiver (RX) nanomachines are mobile, (ii) TX is mobile and RX is fixed, and (iii) TX is fixed and RX is mobile. In particular, a one-dimensional environment with a point TX and a fully-absorbing point RX is considered. Closed-form expressions for the probability density function (PDF) of the first hitting time under the aforementioned mobile scenarios are derived, by characterizing the movement of the nanomachines and information molecules using Brownian motion with positive drift. The derived PDF expressions are validated through particle-based simulations. Based on these results, the performance of molecular communication with on-off keying (OOK) modulation in flow-induced diffusive channels is investigated. In particular, closed-form expressions for the probabilities of detection and false alarm with Likelihood ratio test (LRT) based decision rule, probability of error, and the achievable rate in the presence of inter-symbol interference, counting errors, and noise from the other sources are derived. Simulation results are presented to verify the theoretical results and to yield insights into the system performance for different mobility conditions.