# Qibing Pei

PROFESSOR / VICE CHAIR FOR UNDERGRADUATE EDUCATION
MATERIALS SCIENCE AND ENGINEERING
MECHANICAL AND AEROSPACE ENGINEERING

3111 Engineering V

Email: qpei@seas.ucla.edu
Phone: (310) 825-4217
Fax: (310) 206-7353

Websites

- Qibing Pei

##### RESEARCH AND INTERESTS

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.

##### NOTABLE PUBLICATIONS

- 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).

##### IN THE NEWS

- Scientists Create Artificial Muscle That’s Stronger Than Human Muscle | WebMD, July 2022
- New material could lead to big leap in artificial muscles | Materials Today, July 2022
- New artificial muscle material could help in robotics | Materials Today, July 2022
- Artificial Muscles are Stronger and More Flexible than Real Muscle | Medgadget, July 2022
- Scientists Develop Artificial Muscles That Are Stronger Than Their Biological Counterparts | Next Big What, July 2022
- Thin Bionic Materials Developed to a Stronger, Flexible Artificial Muscle | The Science Times, July 2022
- A New Artificial Muscle is Stronger, More Flexible Than Natural Ones | Interesting Engineering, July 2022

- Developed a Durable Material for Flexible and Strong Artificial Muscles |Hardware News (Turkey), July 2022
- UCLA Could Give Nerds Muscles | Fudzilla, July 2022
- New Durable Material for Flexible Artificial Muscle | Tech Explorist, July 2022
- UCLA Scientists have created a new kind of artificial muscle for machines | KNX-AM (Los Angeles) - Radio, July 2022
- An Artificial Muscle for Machines, Even Stronger and More Flexible Than the Real Thing | KBOI (Boise, ID) News at 10, July 2022
- UCLA Scientists Have Created a New Kind of Artificial Muscle for Machines | KOVR-TV (Sacramento, CA) | CBS 13 News at 5:30pm, July 2022
- Scientists Develop Durable Material for Flexible Artificial Muscles | Knowridge Science Report, July 2022
- Scientists Develop Durable Material for Flexible Artificial Muscles | Health Tech World (UK), July 2022
- Scientists Develop Durable Material for Flexible Artificial Muscles | Phys.org, July 2022
- UCLA Scientists Have Created a New Kind of Artificial Muscle | Action News at 6am (broadcast), July 2022
- New Material for Artificial Muscles Called Stronger, More Flexible Than What's in Body | United Press International, July 2022
- UCLA Researchers Develop New Hydrogel Material for Soft Robots | Daily Bruin, October 2021
- Soft Focus: A Flexible Future for Robots | UCLA Newsroom, June 2021
- Breakthrough in electronic display fabrics could help pave the way for smart clothing | ABC News, March 2021