1. D.S.H. Charrier Dimitri S.H. Charrier

2. D.S.H. Charrier 1 Long term project. SKPM potentiometry. STM potentiometry. A detour… PEDOT:PSS. Giant actuation. Memory. Process partially explained… Drying effect. Sorbitol. 23 } on high performance organics

3. D.S.H. Charrier 1 Long term project. SKPM potentiometry. STM potentiometry. A detour... PEDOT:PSS. Giant actuation. Memory. Process partially explained… Drying effect. Sorbitol. 23

4. D.S.H. Charrier patterned in clean room simulated with COMSOL and MatLab dielectric source gate tip drain active layer lever Our results on test devices L. Bürgi et al, Synthetic Metals, 146, 297 (2004) P3HT T = 165 K D. Charrier et al, submitted

5. D.S.H. Charrier electronic control UHV chamber STM head Home built

6. D.S.H. Charrier before fieldafter field Typical polymer used for organic actuation, polypyrrole = PPy. Largest Strain (elongation) = 36.7 % Redox reactions involveld, PPy↔PPy +. Anionic counter ions to maintain charge neutrality. A huge height increase = 230 nm PEDOT:PSS as active layer (thickness: 60-70 nm) S. Hara et al, Synthetic Metals, 156, 351 (2006) PEDOT PSS

7. D.S.H. Charrier 1 Long term project. SKPM potentiometry. STM potentiometry. A detour... PEDOT:PSS. Giant actuation. Memory. Process partially explained… Drying effect. Sorbitol. 23

8. D.S.H. Charrier SiO 2 Au saturation +- Before field (pristine) After field Initial thickness of PEDOT:PSS = 60-80 nm Spin-coated on glass or on SiO 2 A height increase of about 400% !!!

9. D.S.H. Charrier Saturation (non reversible) + 3.70- 3.7 V Reversible…

10. D.S.H. Charrier Reversible cycles > 12 Switching the bias +/- 4 V Reversible height increase of about 50% +4 0 -4 0 zoom

11. D.S.H. Charrier Best ratio we got On/Off = 466 Optimal organic memory On/Off > 10 000 Hint: electrochemical alteration? + 4 0.5 -4 0.5 V

12. D.S.H. Charrier 1 Long term project. SKPM potentiometry. STM potentiometry. A detour... PEDOT:PSS. Giant actuation. Memory. Process partially explained… Drying effect. Sorbitol. 23

13. D.S.H. Charrier PEDOT:PSS is hygroscopic… At 40-60 % of H 2 0 in air, motion for > 3.5 V At 20 % motion for > 50 V At 13 % no motion visible ‘dry’ ‘wet’ 2 remarks: 2 bumps at around +/-2 V Indication for ionic current ‘wet’ ‘dry’

14. D.S.H. Charrier before after thickness = 90-100 nm + -- sorbitol+anneal: more compact morphology. (sub)conclusion: Other actuation mechanism + - no sorbitol

15. D.S.H. Charrier At positive electrode 2 reactions may occur: PEDOT + PSS - → PEDOT + (PSS - ) + e- (1) Charge neutrality requires movement of PSS - to + electrode. Large volume increase at + electrode Requires mobile PSS (‘large size’)… PEDOT(PSS Na) → PEDOT + (PSS - ) + Na + + e- (2) Charge neutrality requires movement of Na + away from + electrode. Smaller volume change, sign can be + or - Requires mobile Na (‘small size’) Adapted from: Elisabeth Smela, Adv. Mater. 2003, 15, 481. (Review) ‘Wet’ ‘Dry’ ‘Sorbitol’

16. D.S.H. Charrier all images: 500  500 nm 2,  z = 20 nm, done by Alex Nardes anneal at 200  C k B T ~ 40 meV F  L char = (4 V/4  m)  40 nm~ 40 meV (voltage/channel length  ~particle size) Can the field move any material?

17. D.S.H. Charrier Color changing ? Before fieldAfter/during field +- Electrochromic devices Electrochemical reaction at + electrode or PEDOT + moving to anode… ? ‘bluish’ Sorbitol case ‘brownish’

18. D.S.H. Charrier Reaction ? www.baytron.com PEDOT to + ? ?

19. D.S.H. Charrier Prediction of SKPM response via 3D modeling STM as alternative to SKPM: in progress Giant actuation based on PEDOT:PSS Organic memory based on PEDOT:PSS encouraging Actuation partially explained by ionic current and mass transport Activation energy explains the motion Optical changes visible PEDOT + PSS - → PEDOT + (PSS - ) + e- PEDOT(PSS Na) → PEDOT + (PSS - ) + Na + + e-

20. D.S.H. Charrier M2N / TU/e Lukáš Břínek Martijn Kemerink Alex Nardes René Janssen Gérard Wijers OED / TU/e Barry Smalbrugge Tjibbe de Vries