Now Playing
Hardware
The primary objective of this project is to design and implement an integrated algae tank system capable of supporting wet-lab experiments with real-time monitoring and control. By combining hardware modules (audio, sensor, and power) with software integration, we aim to optimize algae growth conditions and collect reproducible data.
Ultimately, the long-term vision is to use the harvested algae biomass for carbon fixation applications and downstream conversion into biodiesel and bioconcrete, contributing to sustainable energy and environmental solutions.
In recent years, audible sound stimulation has emerged as a promising physico-stimulant for enhancing microalgal growth and metabolite production. Several studies have demonstrated that specific sound frequencies or music patterns can significantly influence the physiological performance, photosynthetic efficiency, and accumulation of high-value pigments in microalgae.
A notable study on the halotolerant green microalga Dunaliella salina investigated the effects of audible sound frequencies of 100, 200, 500, and 1000 Hz (sine waves at an intensity of approximately 90 ± 2 dB) under both nitrogen-sufficient and nitrogen-deficient conditions [1]. The results showed that 200 Hz stimulation enhanced dry cell weight and cell division by up to 50% compared with the control. Under nitrogen deficiency, the same frequency not only promoted cell growth but also increased β-carotene accumulation by 37%, whereas nitrogen deficiency alone resulted in only an 18% increase. Conversely, high-frequency stimulation at 1000 Hz suppressed algal growth, suggesting that resonance frequency plays a critical role in regulating algal metabolism.
Similarly, another study focused on Haematococcus pluvialis, a microalga known for its high capacity to produce astaxanthin, a potent antioxidant carotenoid. The algae were cultivated in a 60 L photobioreactor at 25 °C, under 20.3 μmol/m²/s white LED illumination, with daily 8-hour sound treatments for 22 consecutive days [2]. The treatments included two specific pieces of music, Blues for Elle and Far and Wide, with average frequencies of 0.24–0.28 kHz at 60 dB. The results revealed that the Blues for Elle treatment achieved the highest growth rate (0.03 day⁻¹), representing a 58% increase compared with the control. Biomass productivity also reached 3.467 × 10² cells/mL/day, significantly higher than the control (2.297 × 10² cells/mL/day) and the Far and Wide treatment. Kinetic modeling further confirmed these findings, showing that the apparent rate constant (kapp) for Blues for Elle was 0.078 day⁻¹, with a shortened half-life (t₁/₂ = 8.89 days) compared to the control (14.44 days), indicating that sound stimulation accelerated biomass accumulation.
Taken together, these studies demonstrate that both specific pure-tone frequencies (e.g., 200 Hz) and structured music stimuli (e.g., Blues for Elle) can substantially enhance microalgal growth and secondary metabolite production [1], [2]. While the underlying mechanisms may involve improved photosynthetic efficiency, enhanced cell division, and modulation of stress responses, these findings provide compelling evidence that audible sound can serve as a novel, scalable, and low-cost approach to optimize microalgal cultivation. Such strategies hold great promise for the production of high-value pigments (β-carotene, astaxanthin), functional food ingredients, and bioenergy feedstocks.
Emiliania huxleyi is a marine coccolithophore and one of the most significant phytoplankton species in global ocean ecosystems. Because it forms an external shell of calcium carbonate plates (coccoliths), it plays a crucial role in the marine carbon cycle and global climate change research. Consequently, its cultivation methods are well-established [7].
The culture medium provides the essential nutrients for EHUX growth. The most widely used standard media are f/2 Medium and L1 Medium. Both are prepared using a base of filtered and sterilized natural or artificial seawater, which is then enriched with concentrated nutrient salts, trace metals, and vitamins.
Collected from open ocean areas with low pollution, filtered (typically through a 0.22 µm membrane), and sterilized via autoclaving to remove bacteria and other organisms.
Prepared by dissolving commercial sea salts (e.g., Instant Ocean®) in purified water (Milli-Q or RO water) to a specific salinity. This also requires sterilization.
Includes Fe, Mn, Zn, Cu, Co, Mo, chelated with EDTA.
Figure 1: Full System Architecture
The experimental platform was designed as a modular system centered on a custom-built algae cultivation tank integrated with environmental control, sensing, and data acquisition components. Illumination was provided by a programmable LED array, temperature regulation was achieved using a thermoelectric cooling chip, and acoustic stimulation was enabled through an embedded microphone–speaker module.
The system employed three ESP32 microcontrollers to distribute functionalities across monitoring, audio control, and power management subsystems. All ESP32 modules were equipped with Wi-Fi connectivity, enabling real-time data transmission via the IFTTT protocol to a centralized cloud spreadsheet. Local redundancy was achieved through SD card storage, ensuring robustness against network instability.
The operating workflow followed a closed-loop cycle: (1) external stimuli—including light exposure, temperature regulation, and acoustic signals—were applied to the algae culture; (2) sensors continuously measured culture conditions such as temperature, turbidity, and light intensity, while the microphone collected acoustic feedback; (3) ESP32 modules processed and time-stamped the sensor data, displayed the results on OLED screens, and uploaded them to cloud storage; and (4) aggregated datasets were analyzed remotely to correlate environmental conditions with algal growth responses.
Figure 2: Audio module circuit diagram
The audio subsystem comprised a microphone, speaker, MP3 player, volume control, OLED display, and an ESP32 microcontroller. It performed two primary functions:
This module enabled precise acoustic stimulation experiments while providing feedback on energy demands.
Figure 3: Algae tank sensor module circuit diagram
The sensor subsystem functioned as the central hub for environmental data acquisition and included a light intensity sensor (GY-30), thermometer, turbidimeter, time module (DS1302), SD memory card, and OLED display, all managed by the ESP32 microcontroller.
This module ensured robust acquisition of key environmental and biological parameters essential for long-term algal monitoring.
Figure 4: Power module circuit diagram
The power subsystem provided stable energy distribution to the experimental platform. Using an INA3221 current–voltage monitoring sensor, the system measured voltage, current, and power consumption across connected devices in real time, with results displayed on an OLED screen.
Power was supplied through a regulated 12 V source, providing VDD (positive terminal) and GND (negative terminal) lines to all devices. Correct wiring of these terminals was critical, as misconnection could result in irreversible system failure. This module not only supported stable operation but also enabled quantification of energy demands from high-consumption devices such as LEDs and audio components.
The modular algae monitoring system presented in this study offers several distinct advantages. First, the design is low-cost and modular, relying on widely available ESP32 microcontrollers and off-the-shelf sensors, making it suitable for rapid prototyping and replication across laboratories. Second, the architecture supports scalability and redundancy: independent ESP32 units dedicated to monitoring, audio control, and power distribution enable fault isolation and straightforward integration of additional subsystems. Third, the incorporation of real-time cloud synchronization through IFTTT and redundant SD card storage ensures data accessibility, long-term record keeping, and resilience against network instability. Finally, the inclusion of audio stimulation and feedback monitoring provides a novel platform for exploring bioacoustic responses in algae, expanding experimental possibilities beyond conventional light and nutrient regulation.
Despite these strengths, several limitations should be acknowledged. The accuracy and stability of sensors (e.g., turbidity probes and low-cost thermometers) may be affected by environmental conditions such as water salinity, biofouling, and air bubble interference, requiring periodic calibration and protective modifications (e.g., epoxy sealing of the turbidimeter). The reliance on Wi-Fi connectivity introduces potential issues in environments with weak or unstable signals, which may compromise real-time monitoring. Furthermore, the system’s power supply sensitivity poses a risk: incorrect wiring of VDD and GND can result in permanent hardware failure, highlighting the need for strict adherence to electrical safety protocols. Lastly, while the system provides high versatility for experimental control, its compact tank design may not fully replicate large-scale cultivation dynamics, limiting direct extrapolation to industrial settings.
Overall, the system demonstrates strong potential as a flexible and cost-effective research tool, while further refinements in sensor robustness, network reliability, and scale-up strategies are necessary to enhance its applicability in long-term or industrial algal cultivation studies.
Figure 5: system-topview
Figure 6: system-sideview