Leaf‐Inspired Flexible Thermoelectric Generators with High Temperature Difference Utilization Ratio and Output Power in Ambient Air

Abstract

The inherently small temperature difference in air environment restricts the applications of thermoelectric generation in the field of Internet of Things and wearable electronics. Here, a leaf‐inspired flexible thermoelectric generator (leaf‐TEG) that makes maximum use of temperature difference by vertically aligning poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate and constantan thin films is demonstrated. Analytical formulae of the performance scales, i.e., temperature difference utilization ratio (φth) and maximum output power (Pmax), are derived to optimize the leaf‐TEG dimensions. In an air duct (substrate: 36 °C, air: 6 °C, air flowing: 1 m s−1), the 10‐leaf‐TEG shows a φth of 73% and Pmax of 0.38 µW per leaf. A proof‐of‐concept wearable 100‐leaf‐TEG (60 cm2) generates 11 µW on an arm at room temperature. Furthermore, the leaf‐TEG is flexible and durable that is confirmed by bending and brushing over 1000 times. The proposed leaf‐TEG is very appropriate for air convection scenarios with limited temperature differences.

3D Hierarchical Electrodes Boosting Ultrahigh Power Output for Gelatin‐KCl‐FeCN4−/3− Ionic Thermoelectric Cells

“…As a power source, both the output voltage and power density are essential for meeting the needs of IoT sensors. [3] Thermodynamically, the thermoelectric voltage serves as a counterforce to balance the driving force of the temperature gradient. The thermopower (or Seebeck This work aims to increase the instantaneous and continuous output power performances of the quasi-solid-state gelatin-KCl-FeCN 4-/3i-TE cells.…”

Operation of Wearable Thermoelectric Generators Using Dual Sources of Heat and Light

“…Compared with other reported lateral or vertical types of flexible WTEGs under actual operating conditions, our WTEG obtains high power at all ambient temperatures due to the additional heat stemming from sunlight absorption (Figure 5b ). [ 15 , 25 , 32 , 33 , 34 , 36 , 37 , 48 , 49 , 50 ] The decrease in power as the ambient temperature approaches 35 °C is mainly caused by the low Δ T between the body and ambient temperatures. The Δ T from body heat almost disappears, but the Δ T from sunlight absorption remains constant when the ambient temperature is 35 °C.…”

“…WTEG can be divided into lateral and vertical structures depending on the shape of the thermoelectric (TE) leg. Lateral type WTEGs with the TE legs arranged laterally along the substrate are fabricated by printing, [ 2 , 3 , 4 , 5 ] coating, [ 6 , 7 , 8 , 9 , 10 ] or depositing [ 11 , 12 ] flexible organic TE materials such as Poly(3,4‐ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS), [ 6 , 13 , 14 , 15 , 16 ] carbon nanotube (CNT) composites, [ 17 , 18 , 19 , 20 , 21 ] fullerene derivatives, [ 22 , 23 , 24 ] or TE inks made of rigid inorganic TE nanoparticles on flexible substrates. [ 11 , 12 ] Lateral type WTEGs with long and thin TE legs have high Δ T .…”

Multifunctional Wearable Thermoelectrics for Personal Thermal Management

“…The output voltage can be boosted by using voltage step-up converter to deliver sufficient power-supply for thermoelectric PTM. After proper flexibility design, bulk-based thermoelectric PTM can realize a power output of around 100 µW, [32,114,116] the thin film-based thermoelectric PTM can generally generate the power output of about 10 µW, [119,122,123] and the fiber-based PTM can realize a power output of around 5 µW through harvesting human body waste heat. [7,128,134] These wearable thermoelectric PTM can provide reliable and continuous power-supply for electronics by integrating with voltage step-up converter and other elements.…”

“…Such a vertical TED can efficiently utilize the ΔT between human skin and ambient environment. When subjected to wearing output performance test (Figure 10i), [123] the wearable film-based TED can generate an output voltage of 52 and 64 mV under the standing and walking conditions, with a corresponding power output of 7.2 and 11 µW, [123] respectively. Wu et al [122] designed a wearable film-based TED by pasting allinorganic hybrid films (n-type reduced graphene oxide (RGO)/ Bi 2 Te 3 composite and p-type SWCNT/Sb 2 Te 3 composite) on the polyimide substrate.…”