Bubble energy generator

Abstract

Bubbles have been extensively explored as energy carriers ranging from boiling heat transfer and targeted cancer diagnosis. Yet, despite notable progress, the kinetic energy inherent in small bubbles remains difficult to harvest. Here, we develop a transistor-inspired bubble energy generator for directly and efficiently harvesting energy from small bubbles. The key points lie in designing dielectric surface with high-density electric charges and tailored surface wettability as well as transistor-inspired electrode configuration. The synergy between these features facilitates fast bubble spreading and subsequent departure, transforms the initial liquid/solid interface into gas/solid interface under the gating of bubble, and yields an output at least one order of magnitude higher than existing studies. We also show that the output can be further enhanced through rapid bubble collapse at the air/liquid interface and multiple bubbles synchronization. We envision that our design will pave the way for small bubble-based energy harvesting in liquid media.

Fig. 1.. Design and performances of TBENG.

(A) Schematic comparison of the structural characteristics of TBENG and control design without the use of two-electrode design. (B) Photography of an as-fabricated TBENG. (C to E) Comparisons of the open-circuit voltage, short-circuit current, and transferred charge of TBENG with those of the control device, respectively. (F) A bubble impacting on a TBENG can light up the “CITYU” logo consisting of 35 light-emitting diodes (LEDs). The power necessary to light a single LED is 0.12 μW.

Fig. 2.. Working mechanism.

(A) Time-dependent voltage response V and the mapping of voltage with the time-dependent change rate of bubble/PTFE contact area dA_GS/dt. (B and C) Comparison of the interaction between the bubble and the PTFE surface with a BCA of 65° and 135°. (D) Voltage output of TBENG with varying BCAs. (E) Charge density and gas/solid interaction energy under varying BCAs. (F) Linear relationship between V_p and σ(θ_d³ − θ₀³)γ/μ.

Fig. 3.. Energy generation from multiple bubbles and air/water interface.

(A) Bubble dynamics and schematic explanation of bubbles under synchronic mode (I) and nonsynchronic mode (II), respectively. (B) Schematic plots showing the distinct voltage output from synchronic mode and nonsynchronic mode. The red and blue dashed lines denote the voltage output of each individual bubble, respectively. (C) Voltage outputs generated from the TBENG under synchronic mode and nonsynchronic mode, respectively. (D) The accelerated bubble contact, expansion, and collapse dynamics in the air. (E) Output voltage of TBENG with an individual bubble in air reaches up to 70 V. (F) Comparison of electric outputs from tiny bubbles between our work and existing ones (, , , –36).

Fig. 4.. Applications.

(A) Charging capability of TBENG under various capacitors. (B) Electric energy generated from a TBENG can be collected to power a multifunctional sensor for temperature, humidity, and time monitoring. (C) A bubble energy generator device successfully powers a wireless monitoring system for measuring, processing, and transmitting the real-time temperature information to a receiver. (D) Charging and discharging behaviors of a 15-μF capacitor driven by TBENG when powering the wireless temperature monitoring system.