Thermocapillary micromotor

Matrix context

D = disequilibrium row · C = coupling family column. A cell reads the state of the atlas for that pair.

D.01 × C.34 · Temperature gradient × Marangonifamily: Marangoni

Measured or reported performance

1. rotation rateup to 300 r.p.m.device2015
   microfabricated asymmetric gears on a liquid–air interface under wide-field incoherent illumination; the temperature gradient that drives the thermocapillary flow is produced by the light the gear absorbs — rotational work against viscous drag; no load other than the fluid was measured
   refs [3]

Typed bounds on this route

Every limit the atlas holds for this route, as constraint records: reached through bounded_by claims on the route's own entities. Hard bounds (an upper bound or a formula) decide the thermodynamic-bound check above; benchmarks, constitutive relations and resource limits are listed and never decisive. No prose limit exists anywhere (pass 42).

• Carnot limit · formula-bound · hard, applies to this route
  η ≤ 1 − T_c/T_h for any heat engine between reservoirs at T_h and T_c

Steps

1. 01
   Temperature gradient —drives→ Marangoni effectestablishedclaim record

   thermal → kinetic · loss to thermal

   • thermocapillary case: surface tension falls with temperature, so a temperature gradient along the interface drives flow toward the cold side

   liquid · temperature gradient required

   refs [1] [2]
2. 02
   Marangoni effect —produces→ Mechanical motionreplicatedclaim record

   kinetic → mechanical · loss to thermal

   • a floating or interface-bound body whose asymmetry (shape, or where it emits a surfactant or absorbs heat) leaves a net surface-tension force or torque on it
   • the body must be free to move on the interface; a rigid wall only sets up a flow

   liquid

   Two independent groups: thermocapillary microgears (Maggi et al. 2015, light-heated, up to 300 r.p.m.) and solutocapillary camphor rotors carrying magnets past a coil (Frenkel et al. 2019, 10–20 h). Distinct from Marangoni flow turning a rotor: here the Marangoni stress acts on the moving body directly.

   refs [3] [4]
3. 03
   Mechanical motion —converts into→ Mechanical workestablishedclaim record

   mechanical → mechanical · loss to thermal

   refs [5]

Evidence for the complete composition · 1

1. [3]
   C. Maggi et al.. Micromotors with asymmetric shape that efficiently convert light into work by thermocapillary effects (2015)

   Nature Communications 6, 7855 · doi:10.1038/ncomms8855 · record

Evidence for the constituent relations · 5

1. [1]
   L. E. Scriven, C. V. Sternling. The Marangoni Effects (1960)

   Nature 187, 186-188 · doi:10.1038/187186a0 · crossref ✓ 2026-09-20 · record
2. [2]
   Q. Dai et al.. Directional interfacial motion of liquids: Fundamentals, evaluations, and manipulation strategies (2021)

   Tribology International 154, 106749 · doi:10.1016/j.triboint.2020.106749 · crossref ✓ 2026-09-20 · record
3. [3]
   C. Maggi et al.. Micromotors with asymmetric shape that efficiently convert light into work by thermocapillary effects (2015)

   Nature Communications 6, 7855 · doi:10.1038/ncomms8855 · record
4. [4]
   M. Frenkel et al.. Mini-Generator of Electrical Power Exploiting the Marangoni Flow Inspired Self-Propulsion (2019)

   ACS Omega 4, 15265–15268 · doi:10.1021/acsomega.9b02257 · record
5. [5]
   A. Bejan. Advanced Engineering Thermodynamics (4th ed.) (2016)

   Wiley · doi:10.1002/9781119245964 · crossref ✓ 2026-09-19 · record