1 DEMONSTRATION OF CORTICAL RECORDING AND REDUCED INFLAMMATORY RESPONSE USING FLEXIBLE POLYMER NEURAL PROBES LIGA and Biophotonics Lab André Mercanzini, Karen Cheung, Derek Buhl, Marc Boers, Anne Maillard, Philippe, Colin, Jean-Charles Bensadoun, Arnaud Bertsch, Alan Carleton and Philippe Renaud Ecole Polytechnique Fédérale de Lausanne, EPFL, Switzerland University of British Columbia, Vancouver, Canada Massachusetts Institute of Technology, USA NTHU Institute of NanoEngineering and MicroSystem Speaker ： Wen Cheng Yang

2 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion LIGA and Biophotonics Lab

3 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion

4 Introduction Neural interfaces currently help neuroscientists in their study of the brain’s functions and promise to introduce new solutions for conditions such as Parkinson’s and paralysis. In order to decrease this response, flexible probes have been designed by several groups in order to comply with brain tissue motion. Polyimide probes and parylene probes have been developed in order to decrease brain- device compliance mismatch.

5 Introduction Ref ： Leigh R. Hochberg, Mijail D. Serruya, Gerhard M. Friehs, Jon A. Mukand, Maryam Saleh,Abraham H. Caplan, Almut Branner, David Chen, Richard D. Penn & John P. Donoghue. “Neuronal ensemble control of prosthetic devices by a human with tetraplegia”. Nature Vol July 2006

6 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion LIGA and Biophotonics Lab

7 Device fabrication LIGA and Biophotonics Lab Step 1 ： A 500 nm TiW and a 1000 nm sacrificial aluminum layer are deposited on a silicon wafer. Step 2 ： Polyimide is spun to a thickness of 15 µm Step 3 ： Ti/Pt/Ti metal sandwich is deposited at thicknesses of 50nm/200nm/50nm respectively.

8 Device fabrication LIGA and Biophotonics Lab Step 4 ： A second polyimide layer is spun to a thickness of 2 µm Step 5 ： A second polyimide Ti/Pt/Ti sandwich is then deposited and etched thus defining the second layer of electrodes. The final polyimide layer is spun to a thickness of 2um

9 Device fabrication LIGA and Biophotonics Lab Step 6 ： The three layers of polyimide are then etched in an O 2 plasma using the Ti and sacrificial Al as etch stops. The oxide hard mask is dry etched and the wafer is ready for packaging and device release

10 Outline LIGA and Biophotonics Lab SEM image of the fabricated device.

11 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion LIGA and Biophotonics Lab

12 Device packaging LIGA and Biophotonics Lab Microscope image demonstrating crossover of metal layers and electrode sites. A packaged flexible neural probe device

13 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion LIGA and Biophotonics Lab

14 Electrical characterization LIGA and Biophotonics Lab Impedance magnitude and phase for one electrode site Figure shows the typical impedance spectrum of devices.There was no apparent difference in impedance between the bottom and top metal layers.

15 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion

16 Acute recordings EEG recordings from 16 electrode sites distinguishing 2 single units Demonstrates local field potential recordings identifying two single units in the mouse cortex. All 16 electrode sites were active.

17 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion

18 Histology General staining for cells with DAPI Staining for microglia, CD11b (green) and astrocytes, GFAP (red).

19 Outline Introduction Device fabrication Device packaging Electrical characterization Acute recordings Histology Conclusion

20 Conclusion Due to the smaller neural probe size, and brain-probe compliance match, we have demonstrated reduced insertion and chronic damage using polyimide microfabricated probes.

21 LIGA and Biophotonics Lab Thanks for your attendance.