Professor Qibing Pei
Tel. (310) 825-4217
FAX (310) 206-7353
Our Soft Materials Research Laboratory studies electroactive polymers and nanostructured hybrid materials. The research focuses on molecular synthesis and nanofabrication for the development of new polymers and nanostructures with desired electronic, photonic, and/or mechanical properties. The applications of these materials are many folds, including flexible electronics, artificial muscles, photovoltaics, wind energy generation, radiation detection and protection, and biologically-inspired systems to name a few. Current activities include:
Artificial Muscles: These are based on dielectric elastomers exhibiting electrically-induced strains as high as 300%. The polymer transducers have such advantages as high energy and power densities, quietness, mechanical compliancy (for shock resistance and impedance matching), high efficiency, lightweight, and low cost. To improve the device performance and reliability, interpenetrating polymer networks are being studied as a new generation of electroelastomers. Fault tolerance is being introduced as a means to prolong operation lifetime. Our projects involve mechanical design, fabrication, and testing of polymer actuators and generators. Bistable electroactive polymer has been introduced for large-strain, rigid-to-rigid actuation. This material is being employed to fabricate Braille electronic readers.
Flexible electronics: We are developing electronic devices that are flexible and stretchable. A key component is stretchable transparent electrodes based on composites of carbon nanotubes and silver nanowires. The composites electrodes have sheet resistance and transmission of visible light comparable to indium tin oxide coated on PET and glass. Polymer light emitting diodes and solar cells fabricated on the composite electrodes perform as well as or better than control devices on ITO/glass. Using the composite electrodes, we have demonstrated polymer LEDs wherein the active area is stretchable.
Nanostructured hybrid materials: Composites of inorganic compounds and conjugated polymers are prepared with controlled nanostructures for photovoltaics or radiation detection. We synthesized CdS nanorod arrays by electrochemical self-assembly, and CdS thin coating by chemical bath deposition. High-Z nanoparticle polymer composites are studied for gamma and X-ray scintillation.
Synthesis of conjugated polymers: The band gap, band edges (electron affinity and ionization potential), optical absorption, photoluminescence color and quantum efficiency, and carrier mobility can be modulated through the conjugated backbone or side chains, structural regularity, molecular weight, purity, and molecular ordering. We can thus tailor conjugated polymers for different applications such as light emitting diodes, solar cells, thin film transistors, and sensors. We fabricate semiconductor devices (LEDs, solar cells) using the selected polymers.
Electronic polymer synthesis, electroactive polymer artificial muscles, polymer actuators, polymer electronic devices.
Prospective graduate students and postdoctoral researchers with the following specialties are welcome to apply: synthesis of conjugated polymers; solution-based nanofabrication; polymer processing; thin film electronic devices; organic synthesis; actuators and sensors.
We anticipate multiple postdoctoral openings to develop dielectric elastomers for muscle-like actuation, stretchable polymer electronics, and solution-based coating of polymeric and nanomaterials. Candidates with strong hands-on experience in at least three of these fields are encouraged to apply: synthesis of nanocomposites (e.g. graphene nanocomposites), synthesis of conjugated polymers, nanomaterials processing, polymer coating, solution processing of carbon nanotubes and graphene, slot die coating, soft polymer actuator fabrication, high thermal conductive materials, characterization of thermal conductivity.
C. Murray, D. McCoul, E. Sollier, T. Ruggiero, X. Niu, Q. Pei, D. Di Carlo, “Electro-adaptive microfluidics for active tuning of channel geometry using polymer actuators”, Microfluidics and Nanofluidics, 14(1), 345-358 (2013).
H. Stoyanov, P. Brochu, X. Niu, C. Lai, S. Yun and Q. Pei, “Long lifetime, fault-tolerant freestanding actuators based on a silicone dielectric elastomer and self-clearing carbon nanotube compliant electrodes,” RSC Advances, 3 (7), 2272 – 2278 (2013).
X. Niu, H. Stoyanov, W. Hu, R. Leo, P. Brochu, Q. Pei, “Synthesizing a New Dielectric Elastomer Exhibiting Large Actuation Strain and Suppressed Electromechanical Instability without Prestretching”, J. Polymer Science, Part B: Polymer Physics, 51, 197–206 (2013).
L. Li, J. Liu, Z. Yu, Q. Pei, “Efficient White Polymer Light-Emitting Diodes Employing a Silver Nanowire-Polymer Composite Electrode”, Phys. Chem. Chem. Phys., 14 (41), 14249 – 14254 (2012).
W. Hu, X. Niu, L. Li, S. Yun, Z. Yu, and Q. Pei, “Intrinsically stretchable transparent electrodes based on silver-nanowire–crosslinked-polyacrylate composites”, Nanotechnology 23, 344002 (2012).
H. Stoyanov, P. Brochu, X, Niu, E.D. Gaspera, Q. Pei, “Dielectric elastomer transducers with enhanced force output and work density”, Applied Physics Letters, 100, 262902 (2012).
S. Yun, X. Niu, Z. Yu, W. Hu, P. Brochu, Q. Pei, “Compliant Silver Nanowire-Polymer Composite Electrodes for Bistable Large Strain Actuation”, Advanced Materials, 24, 1321-1327 (2012).
L. Li, Z. Yu, W. Hu, C.-H. Chang, Q. Chen and Q. Pei, “Efficient Flexible Phosphorescent Polymer Light-Emitting Diodes Based on Silver Nanowire-Polymer Composite Electrode”, Advanced Materials, 23(46), 5563–5567 (2011).
Z. Yu, L. Li, Q. Zhang, W. Hu, Q. Pei, “Silver Nanowire-Polymer Composite Electrodes for Efficient Polymer Solar Cells”, Adv Mater. 23(38), 4453-4457 (2011).
Z. Yu, X. Niu, Z. Liu, Q. Pei, “Intrinsically Stretchable Polymer Light-Emitting Devices Using Carbon Nanotube-Polymer Composite Electrodes”, Adv. Mater. 23 (34), 2011, 3989–3994 (2011).
J. Liu, L. Li, C. Gong, Z. Yu, Q. Pei, “An Ambipolar Poly(Meta-Phenylene) Copolymer with High Triplet Energy to Host Blue and Green Electrophosphorescence”, J. Mater. Chem., 21, 9772-9777 (2011).
L. Li, J. Liu, Z. Yu, and Q. Pei, “Highly Efficient Blue Phosphorescent Polymer Light-Emitting Diodes by Using Interfacial Modification”, Appl. Phys. Lett. 98 (20), Article No: 201110 (May 2011).
L. Li, J. Liu, Z. Yu, and Q. Pei, “Highly Efficient Blue Phosphorescent Polymer Light-Emitting Diodes by Using Interfacial Modification”, Appl. Phys. Lett. 98 (20), Article No: 201110 (2011).
J. Liu, L. Li, Q. Pei, “Conjugated Polymer as Host for High Efficiency Blue and White Electrophosphorescence”, Macromolecules 44 (8), 2451-2456 (2011).
Z. Yu, M. Wang, G. Lei, J. Liu, L. Li, Q. Pei, “Stabilizing the Dynamic p-i-n Junction in Polymer Light-Emitting Electrochemical Cells”, J. Phys. Chem. Lett. 2, 367-372 (2011).
Z. Yu, Q. Zhang , L. Li , Q. Chen , X. Niu , J. Liu , and Q. Pei, “Highly Flexible Silver Nanowire Electrodes for Shape-Memory Polymer Light-Emitting Diodes,” Adv Mater. 23, 664-668 (2011).
J. Liu, Q. Pei, “Poly(m-phenylene): Conjugated Polymer Host with High Triplet Energy for Efficient Blue Electrophosphorescence,” Macromolecules, 43, 9608-9612 (2010).
J. Liu, Q. Pei, “Electrophosphorescent Polymers for High-Efficiency Light-Emitting Diodes,” Current Org. Chem. 14, 2133-2144 (2010).
W. Yuan, H. Li, P. Brochu, X. Niu and Q. Pei, “Fault-tolerant silicone dielectric elastomers”, International J. Smart and Nano Materials, Vol. 1, No. 1, pp 40–52 (2010).
H. Zhang, L. Düring, G. Kovacs, W. Yuan, X. Niu, Q. Pei, “Interpenetrating polymer networks based on acrylic elastomers and plasticizers with improved actuation temperature range”, Polymer International, 59, 384-390 (2010.
P. Brochu, Q. Pei, “Advances in Dielectric Elastomers for Actuators and Artificial Muscles,” Macromol. Rapid Commun. 2010, 31, 10-36 (2010).
Z. Yu, W. Yuan, P. Brochu, B. Chen, Z. Liu, Q. Pei, “Large-strain, Rigid-to-rigid Deformation of Bistable Electroactive Polymers”, Appl. Phys. Lett. 95, 192904 (2009).
Z. Yu, L. Hu, Z. Liu, M. Sun, M. Wang, G. Grüner, Q. Pei, “Fully Bendable Polymer Light Emitting Devices with Carbon Nanotubes as Cathode and Anode,” Appl. Phys. Lett. Vol. 95, #203304, pp 1-3 (2009).
W. Yuan, P. Brochu, S.M. Ha, Q. Pei, “Dielectric Oil Coated Single-walled Carbon Nanotube Electrodes for Stable, Large-strain Actuation with Dielectric Elastomers”, Sensors and Actuators A: Physical, Vol. 155, pp 278–284 (2009).
Q. Pei, “Forward”, Iontronics: Ionic Carriers in Organic Electronic Materials and Devices. Editor(s): J. Leger, M. Berggren, S. Carter, CRC Press. Published Oct. 14, 2010.
Y. Li, Q. Pei, “Electrochemistry of Conjugated Polymers”, Iontronics: Ionic Carriers in Organic Electronic Materials and Devices. Editor(s): J. Leger, M. Berggren, S. Carter, CRC Press. Published Oct. 14, 2010.
S.M. Ha, Q. Pei, R. Pelrine, S. Stanford, “Interpenetrating Polymer Networks as High Performance Dielectric Elastomers,” in “Dielectric Elastomers as Electromechanical Transducers: Fundamentals, materials, devices, models & applications of an emerging electroactive polymer technology.” Eds. F. Carpi, D. DeRossi, R. Kornbluh, R. Pelrine, P. Sommer-Larsen, Chapter 5. Publisher: Elsevier, January 2008.
M. Rosenthal, Q. Pei, “Multiple-degrees-of-freedom Roll Actuators,” in “Dielectric Elastomers as Electromechanical Transducers: Fundamentals, materials, devices, models & applications of an emerging electroactive polymer technology.” Eds. F. Carpi, D. DeRossi, R. Kornbluh, R. Pelrine, P. Sommer-Larsen, Chapter 9. Publisher: Elsevier, January 2008.
Scientific Advisory Board, Annual Conferences of Electroactive Polymer Actuators and Materials, since 2006.
Scientific Committee member, International Conference on Smart Materials and Nanotechnology in Engineering, since 2008.
Member, California NanoSystems Institute, UCLA, since 2006.
Faculty member, Materials Creation Training Program, UCLA, since 2006.
Members of MRS and ACS
Fellow of SPIE.
Research Group/Lab: http://www.peigroup.seas.ucla.edu/
MSE 104 Science of Engineering Materials
MSE 150 Introduction to Polymers
MSE 251 Chemistry of Soft Materials
MSE 252 Organic Polymer Electronic Materials
3121-H Engineering V
UCLA, HSSEAS School of Engineering & Applied Sciences
Department of Materials Science and Engineering
410 Westwood Plaza
3111 Engineering V
Los Angeles, CA 90095-1595