Photothermal-Electric Excited Droplet Multibehavioral Manipulation

The light-excited droplet manipulation is crucial in diverse industrial and health domains, owning to the merits of real-time control and noncontact operation. However, strong driving forces and high-precision maneuverability for splitting or mixing are still the challenges. Here a novel concept of configurating pyroelectric crystal surface is put forward to carry out multifunctional manipulation of the droplet by optical-thermal-electrical effect. Dipole-like electric charge distribution is excited around the light spot to generate sharper inversion of electric field gradient and 10-fold stronger dielectrophoretic （DEP） force than conventional photopyroelectric approaches. Both the stable mode and metastable-oscillation mode are found and can be positively used to make on-demand sliding and inside mixing of droplets. Especially, various droplets with the surface tension ranging from 25.7 to 85.4 mN m⁻¹ can be split by light. The present droplet manipulation technique demonstrates its promising applications in cargo transportation, combinatorial chemistry and biomedical analysis.