Pingyu Wang

All Publications

• Thermal Processing Creates Water-Stable PEDOT:PSS Films for Bioelectronics. Advanced materials (Deerfield Beach, Fla.) Doshi, S., Forner, M. O., Wang, P., Hadwe, S. E., Jin, A. T., Dijk, G., Brinson, K., Lim, J., Dominguez-Alfaro, A., Lim, C. Y., Salleo, A., Barone, D. G., Hong, G., Brongersma, M. L., Melosh, N. A., Malliaras, G. G., Keene, S. T. 2025: e2415827

  Abstract

  Organic mixed ionic-electronic conductors have emerged as a key material for the development of bioelectronic devices due to their soft mechanical properties, biocompatibility, and high volumetric capacitance. In particular, PEDOT:PSS has become a choice material because it is highly conductive, easily processible, and commercially available. However, PEDOT:PSS is dispersible in water, leading to delamination of films when exposed to biological environments. For this reason, chemical cross-linking agents such as (3-glycidyloxypropyl)trimethoxysilane (GOPS) are used to stabilize PEDOT:PSS films in water, but at the cost of decreased electrical performance. Here, it is shown that PEDOT:PSS thin films become water-stable by simply baking at high temperatures (>150 °C) for a short time (≈ 2 min). It is shown that heat-treated PEDOT:PSS films are as stable as their chemically-cross-linked counterparts, with their performance maintained for >20 days both in vitro and in vivo. The heat-treated films eliminate electrically insulating cross-linkers, resulting in a 3× increase in volumetric capacitance. Applying thermal energy using a focused femtosecond laser enables direct patterning of 3D PEDOT:PSS microstructures. The thermal treatment method is compatible with a wide range of substrates and is readily substituted into existing workflows for manufacturing devices, enabling its rapid adoption in the field of bioelectronics.

  View details for DOI 10.1002/adma.202415827

  View details for PubMedID 40025942

• Direct-Print 3D Electrodes for Large-Scale, High-Density, and Customizable Neural Interfaces. Advanced science (Weinheim, Baden-Wurttemberg, Germany) Wang, P., Wu, E. G., Uluşan, H., Zhao, E. T., Phillips, A. J., Kling, A., Hays, M. R., Vasireddy, P. K., Madugula, S., Vilkhu, R., Hierlemann, A., Hong, G., Chichilnisky, E. J., Melosh, N. A. 2024: e2408602

  Abstract

  Silicon-based microelectronics can scalably record and modulate neural activity at high spatiotemporal resolution, but their planar form factor poses challenges in targeting 3D neural structures. A method for fabricating tissue-penetrating 3D microelectrodes directly onto planar microelectronics using high-resolution 3D printing via 2-photon polymerization and scalable microfabrication technologies are presented. This approach enables customizable electrode shape, height, and positioning for precise targeting of neuron populations distributed in 3D. The effectiveness of this approach is demonstrated in tackling the critical challenge of interfacing with the retina-specifically, selectively targeting retinal ganglion cell (RGC) somas while avoiding the axon bundle layer. 6,600-microelectrode, 35 µm pitch, tissue-penetrating arrays are fabricated to obtain high-fidelity, high-resolution, and large-scale retinal recording that reveals little axonal interference, a capability previously undemonstrated. Confocal microscopy further confirms the precise placement of the microelectrodes. This technology can be a versatile solution for interfacing silicon microelectronics with neural structures at a large scale and cellular resolution.

  View details for DOI 10.1002/advs.202408602

  View details for PubMedID 39588825

• Enhanced Thin-Film Encapsulation Through Micron-Scale Anchors ADVANCED FUNCTIONAL MATERIALS Hemed, N., Pham, A., Zhao, E. T., Wang, P., Melosh, N. A. 2024

  View details for DOI 10.1002/adfm.202402661

  View details for Web of Science ID 001216273400001

• A 1024-Channel 268 nW/pixel 36×36 μm2/channel Data-Compressive Neural Recording IC for High-Bandwidth Brain-Computer Interfaces. IEEE journal of solid-state circuits Jang, M., Hays, M., Yu, W. H., Lee, C., Caragiulo, P., Ramkaj, A., Wang, P., Phillips, A. J., Vitale, N., Tandon, P., Yan, P., Mak, P. I., Chae, Y., Chichilnisky, E. J., Murmann, B., Muratore, D. G. 2024; 59 (4): 1123-1136

  Abstract

  This paper presents a data-compressive neural recording IC for single-cell resolution high-bandwidth brain-computer interfaces. The IC features wired-OR lossy compression during digitization, thus preventing data deluge and massive data movement. By discarding unwanted baseline samples of the neural signals, the output data rate is reduced by 146× on average while allowing the reconstruction of spike samples. The recording array consists of pulse position modulation-based active digital pixels with a global single-slope analog-to-digital conversion scheme, which enables a low-power and compact pixel design with significantly simple routing and low array readout energy. Fabricated in a 28-nm CMOS process, the neural recording IC features 1024 channels (i.e., 32 × 32 array) with a pixel pitch of 36 μm that can be directly matched to a high-density microelectrode array. The pixel achieves 7.4 μVrms input-referred noise with a -3 dB bandwidth of 300-Hz to 5-kHz while consuming only 268 nW from a single 1-V supply. The IC achieves the smallest area per channel (36 × 36 μm2) and the highest energy efficiency among the state-of-the-art neural recording ICs published to date.

  View details for DOI 10.1109/jssc.2023.3344798

  View details for PubMedID 39391047

  View details for PubMedCentralID PMC11463976

• A 1024-Channel 268-nW/Pixel 36 x 36 μm<SUP>2</SUP>/Channel Data-Compressive Neural Recording IC for High-Bandwidth Brain-Computer Interfaces IEEE JOURNAL OF SOLID-STATE CIRCUITS Jang, M., Hays, M., Yu, W., Lee, C., Caragiulo, P., Ramkaj, A. T., Wang, P., Phillips, A. J., Vitale, N., Tandon, P., Yan, P., Mak, P., Chae, Y., Chichilnisky, E. J., Murmann, B., Muratore, D. G. 2023

  View details for DOI 10.1109/JSSC.2023.3344798

  View details for Web of Science ID 001137386500001

• A CMOS-based highly scalable flexible neural electrode interface. Science advances Zhao, E. T., Hull, J. M., Mintz Hemed, N., Uluşan, H., Bartram, J., Zhang, A., Wang, P., Pham, A., Ronchi, S., Huguenard, J. R., Hierlemann, A., Melosh, N. A. 2023; 9 (23): eadf9524

  Abstract

  Perception, thoughts, and actions are encoded by the coordinated activity of large neuronal populations spread over large areas. However, existing electrophysiological devices are limited by their scalability in capturing this cortex-wide activity. Here, we developed an electrode connector based on an ultra-conformable thin-film electrode array that self-assembles onto silicon microelectrode arrays enabling multithousand channel counts at a millimeter scale. The interconnects are formed using microfabricated electrode pads suspended by thin support arms, termed Flex2Chip. Capillary-assisted assembly drives the pads to deform toward the chip surface, and van der Waals forces maintain this deformation, establishing Ohmic contact. Flex2Chip arrays successfully measured extracellular action potentials ex vivo and resolved micrometer scale seizure propagation trajectories in epileptic mice. We find that seizure dynamics in absence epilepsy in the Scn8a+/- model do not have constant propagation trajectories.

  View details for DOI 10.1126/sciadv.adf9524

  View details for PubMedID 37285436

  View details for PubMedCentralID PMC10246892

• Direct-print three-dimensional electrodes for large- scale, high-density, and customizable neural inter- faces. bioRxiv : the preprint server for biology Wang, P., Wu, E. G., Uluşan, H., Phillips, A. J., Rose Hays, M., Kling, A., Zhao, E. T., Madugula, S., Vilkhu, R. S., Vasireddy, P. K., Hier-Lemann, A., Hong, G., Chichilnisky, E. J., Melosh, N. A. 2023

  Abstract

  Silicon-based planar microelectronics is a powerful tool for scalably recording and modulating neural activity at high spatiotemporal resolution, but it remains challenging to target neural structures in three dimensions (3D). We present a method for directly fabricating 3D arrays of tissue-penetrating microelectrodes onto silicon microelectronics. Leveraging a high-resolution 3D printing technology based on 2-photon polymerization and scalable microfabrication processes, we fabricated arrays of 6,600 microelectrodes 10-130 μm tall and at 35-μm pitch onto a planar silicon-based microelectrode array. The process enables customizable electrode shape, height and positioning for precise targeting of neuron populations distributed in 3D. As a proof of concept, we addressed the challenge of specifically targeting retinal ganglion cell (RGC) somas when interfacing with the retina. The array was customized for insertion into the retina and recording from somas while avoiding the axon layer. We verified locations of the microelectrodes with confocal microscopy and recorded high-resolution spontaneous RGC activity at cellular resolution. This revealed strong somatic and dendritic components with little axon contribution, unlike recordings with planar microelectrode arrays. The technology could be a versatile solution for interfacing silicon microelectronics with neural structures and modulating neural activity at large scale with single-cell resolution.

  View details for DOI 10.1101/2023.05.30.542925

  View details for PubMedID 37398164

  View details for PubMedCentralID PMC10312573

• Automated and Wireless Accelerated Heat Soak Testing System to Assess Hermetic Failure Mechanism of Inductively Powered Implantable Medical Applications ADVANCED MATERIALS TECHNOLOGIES Yeon, P., Kim, M., Wang, P., Kim, C., Brand, O., Ghovanloo, M. 2023

  View details for DOI 10.1002/admt.202201973

  View details for Web of Science ID 000962992900001

• A scalable bonding technique for the development of next-generation brain-machine interfaces Wang, P., Goh, T., Hemed, N., Melosh, N., IEEE IEEE. 2019: 863–66

  View details for Web of Science ID 000469933200210

• Direct microfabrication of oxide patterns by local electrodeposition of precisely positioned electrolyte: the case of Cu2O SCIENTIFIC REPORTS Wang, P., Roberts, R. C., Ngan, A. W. 2016; 6: 27423

  Abstract

  An efficient technique for writing 2D oxide patterns on conductive substrates is proposed and demonstrated in this paper. The technique concerns a novel concept for selective electrodeposition, in which a minimum quantity of liquid electrolyte, through an extrusion nozzle, is delivered and manipulated into the desired shape on the substrate, meanwhile being electrodeposited into the product by an applied voltage across the nozzle and substrate. Patterns of primarily Cu2O with 80~90% molar fraction are successfully fabricated on stainless steel substrates using this method. A key factor that allows the solid product to be primarily oxide Cu2O instead of metal Cu - the product predicted by the equilibrium Pourbaix diagram given the unusually large absolute deposition voltage used in this method, is the non-equilibrium condition involved in the process due to the short deposition time. Other factors including the motion of the extrusion nozzle relative to the substrate and the surface profile of the substrate that influence the electrodeposition performance are also discussed.

  View details for DOI 10.1038/srep27423

  View details for Web of Science ID 000377011300001

  View details for PubMedID 27255188

  View details for PubMedCentralID PMC4891777