@article{qiang_artoni_seo_culaclii_hogan_zhao_zhong_han_wang_lo_et al._2018, title={Transparent arrays of bilayer-nanomesh microelectrodes for simultaneous electrophysiology and two-photon imaging in the brain}, volume={4}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.aat0626}, abstractNote={We report a transparent, bilayer-nanomesh microelectrode array for concurrent electrophysiology recording and two-photon imaging. Transparent microelectrode arrays have emerged as increasingly important tools for neuroscience by allowing simultaneous coupling of big and time-resolved electrophysiology data with optically measured, spatially and type resolved single neuron activity. Scaling down transparent electrodes to the length scale of a single neuron is challenging since conventional transparent conductors are limited by their capacitive electrode/electrolyte interface. In this study, we establish transparent microelectrode arrays with high performance, great biocompatibility, and comprehensive in vivo validations from a recently developed, bilayer-nanomesh material composite, where a metal layer and a low-impedance faradaic interfacial layer are stacked reliably together in a same transparent nanomesh pattern. Specifically, flexible arrays from 32 bilayer-nanomesh microelectrodes demonstrated near-unity yield with high uniformity, excellent biocompatibility, and great compatibility with state-of-the-art wireless recording and real-time artifact rejection system. The electrodes are highly scalable, with 130 kilohms at 1 kHz at 20 μm in diameter, comparable to the performance of microelectrodes in nontransparent Michigan arrays. The highly transparent, bilayer-nanomesh microelectrode arrays allowed in vivo two-photon imaging of single neurons in layer 2/3 of the visual cortex of awake mice, along with high-fidelity, simultaneous electrical recordings of visual-evoked activity, both in the multi-unit activity band and at lower frequencies by measuring the visual-evoked potential in the time domain. Together, these advances reveal the great potential of transparent arrays from bilayer-nanomesh microelectrodes for a broad range of utility in neuroscience and medical practices.}, number={9}, journal={SCIENCE ADVANCES}, author={Qiang, Yi and Artoni, Pietro and Seo, Kyung Jin and Culaclii, Stanislav and Hogan, Victoria and Zhao, Xuanyi and Zhong, Yiding and Han, Xun and Wang, Po-Min and Lo, Yi-Kai and et al.}, year={2018}, month={Sep} }
 @misc{integrated circuit devices having on-chip adaptive bandwidth buses and related methods_2006, volume={7,110,420}, publisher={Washington, DC: U.S. Patent and Trademark Office}, year={2006} }
 @article{yuce_liu_2005, title={A low-power multirate differential PSK receiver for space applications}, volume={54}, ISSN={["1939-9359"]}, DOI={10.1109/TVT.2005.858196}, abstractNote={Wireless communication for deep-space and satellite applications needs to accommodate the Doppler shift caused by the movement of the space vehicle and should consume low power to conserve the onboard power. A low-power phase-shift keying (PSK) receiver has been designed for such applications. The receiver employs double differential detection to be robust against Doppler shift and uses subsampling with a 1-bit A/D converter and digital decimation architecture at the front end to achieve low-power consumption. The receiver is also designed to be programmable to operate using single-stage differential detection instead of double-stage differential detection at low Doppler rates to obtain optimum performance. Furthermore, the baseband can be employed in either direct subsampling or intermediate frequency (IF)-sampling front ends. Both front ends offer minimal power consumption and differ from traditional types by replacing some conventional analog components such as a voltage-controlled oscillator, mixer, or phase-locked loop with their digital counterparts. This eliminates problems due to dc offset, dc voltage drifts, and low-frequency (LF) noise. The paper also includes a brief discussion of the nonidealities existing in real applications. The proposed phase shift keying (PSK) receiver supports a wide range of data rates from 0.1-100 Kbps and has been implemented in a CMOS process.}, number={6}, journal={IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY}, author={Yuce, MR and Liu, WT}, year={2005}, month={Nov}, pages={2074–2084} }
 @misc{nishida_liu_2005, title={Interpolating sense amplifier circuits and methods of operating the same}, volume={6850096}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Nishida, Y. and Liu, W.}, year={2005} }
 @article{bashirullah_liu_cavin_edwards_2004, title={A hybrid current/voltage mode on-chip signaling scheme with adaptive bandwidth capability}, volume={12}, ISSN={["1557-9999"]}, DOI={10.1109/tvlsi.2004.831481}, abstractNote={This brief describes an adaptive bandwidth bus architecture based on hybrid current/voltage mode repeaters for long global RC interconnect static busses that achieves high-data rates while minimizing the static power dissipation associated with current-mode (CM) signaling. An experimental adaptive bandwidth bus test chip fabricated in AMI 1.6-/spl mu/m Bulk CMOS indicates a reduction in power dissipation of approximately 62% over CM sensing and an increase in maximum data rate of 40% over voltage-mode signaling.}, number={8}, journal={IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS}, author={Bashirullah, R and Liu, WT and Cavin, R and Edwards, D}, year={2004}, month={Aug}, pages={876–880} }
 @article{demarco_liu_singh_lazzi_humayun_weiland_2003, title={An arbitrary waveform stimulus circuit for visual prostheses using a low-area multibias DAC}, volume={38}, ISSN={["0018-9200"]}, DOI={10.1109/JSSC.2003.817264}, abstractNote={Attempts are underway to construct a retinal prosthesis to recover limited vision for blind patients with retinitis pigmentosa using implantable electronic devices. These microchips provide electrical stimulation to damaged retinal tissues using an array of stimulus circuits. This paper describes improvements to conventional circuit designs with significantly decreased implementation area and the ability to support arbitrary stimulus waveforms where an array of such stimulus circuits is required. This yields greater spatial resolution in stimulation owing to more stimulus circuits per chip area. Also introduced are digital-to-analog converter gain prescalar and dc-offset circuits which tune the stimulus circuits to an optimally effective range due to variation in retinal degradation. The prototype chip was fabricated by MOSIS in 1.2-/spl mu/m CMOS technology.}, number={10}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={DeMarco, SC and Liu, WT and Singh, PR and Lazzi, G and Humayun, MS and Weiland, JD}, year={2003}, month={Oct}, pages={1679–1690} }
 @article{demarco_lazzi_liu_weiland_humayun_2003, title={Computed SAR and thermal elevation in a 0.25-mm 2-D model of the human eye and head in response to an implanted retinal stimulator - Part I: Models and methods}, volume={51}, ISSN={["1558-2221"]}, DOI={10.1109/TAP.2003.816395}, abstractNote={Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Attempts are under way to construct a visual prosthesis to recover a limited sense of vision for these patients with the aid of implantable electronic devices. The function of these microchips is to provide electrical stimulation to existing viable retinal tissues - living ganglion and bipolar cells - using an array of on-chip stimulus circuits, while the dominant mechanism for power and data communication for these implanted devices has been wireless inductive telemetry using coils. This paper describes methods and models used to estimate the heating induced in the human eye and surrounding head tissues subject to the operation of this retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model has been developed with the aid of a new semiautomatic graphical segmentation algorithm. Finite-difference-based numerical methods for both electromagnetic and thermal modeling have been used to determine the influence of the specific absorption rate (associated with 2-MHz inductive coupling to the implant) and of stimulator integrated circuit (IC) power on tissue heating under different operational conditions and different hypothesis on choroidal blood flow and properties of the complex implanted circuitry. Results, provided in Part II of this paper, show that temperature increases of approximately 0.6 and 0.4/spl deg/C are induced in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, for a 60-electrode retinal prosthesis chip. Correspondent temperature rises of approximately 0.19 and 0.004/spl deg/C on the retina are obtained for these cases. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={DeMarco, SC and Lazzi, G and Liu, WT and Weiland, JD and Humayun, MS}, year={2003}, month={Sep}, pages={2274–2285} }
 @article{lazzi_demarco_liu_weiland_humayun_2003, title={Computed SAR and thermal elevation in a 0.25-mm 2-D model of the human eye and head in response to an implanted retinal stimulator - Part II: Results}, volume={51}, ISSN={["0018-926X"]}, DOI={10.1109/TAP.2003.816394}, abstractNote={Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Attempts are under way to construct a visual prosthesis to recover a limited sense of vision for these patients with the aid of implantable electronic devices. The function of these microchips is to provide electrical stimulation to existing viable retinal tissues—living ganglion and bipolar cells—using an array of on-chip stimulus circuits, while the dominant mechanism for power and data communication for these implanted devices has been wireless inductive telemetry using coils. This paper describes methods and models used to estimate the heating induced in the human eye and surrounding head tissues subject to the operation of this retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model has been developed with the aid of a new semiautomatic graphical segmentation algorithm. Finite-difference-based numerical methods for both electromagnetic and thermal modeling have been used to determine the influence of the specific absorption rate (associated with 2-MHz inductive coupling to the implant) and of stimulator integrated circuit (IC) power on tissue heating under different operational conditions and different hypothesis on choroidal blood flow and properties of the complex implanted circuitry. Results, provided in Part II of this paper, show that temperature increases of approximately 0.6 and 0.4 C are induced in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, for a 60-electrode retinal prosthesis chip. Correspondent temperature rises of approximately 0.19 and 0.004C on the retina are obtained for these cases. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.}, number={9}, journal={IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION}, author={Lazzi, G and DeMarco, SC and Liu, WT and Weiland, JD and Humayun, MS}, year={2003}, month={Sep}, pages={2286–2295} }
 @article{liu_sivaprakasam_singh_bashirullah_wang_2003, title={Electronic visual prosthesis}, volume={27}, ISSN={["1525-1594"]}, DOI={10.1046/j.1525-1594.2003.07306.x}, abstractNote={Abstract:  Retinitis pigmentosa (RP) and age‐related macular degeneration (AMD) are incurable diseases that result in profound vision loss due to degeneration of the light sensing photoreceptors. However, the discovery that direct electrical stimulation of the retinal neurons creates visual sensation has inspired prosthetic devices aimed to restore useful vision in RP/AMD patients. The approach to one such electronic visual prosthesis is described in this article. The prosthesis consists of an external unit and an internal unit. The communication link has three components—power and data transfer from the external to the internal unit, and data transfer from the internal to the external unit. A novel method of integrating power transfer and back telemetry is described here. The goal is to design a stimulator chip with a small area with low power consumption. This chip, capable of stimulating 60 dedicated electrodes, is fabricated using AMI 1.2 µm process technology and the results are presented. Improvements in the design to increase the number of outputs to 1,000 have been discussed. The new circuit is aimed at increasing the circuit density, reducing power per stimulus, and meeting the requirements more closely than the previous designs. The results of the designed  chip  are presented.}, number={11}, journal={ARTIFICIAL ORGANS}, author={Liu, WT and Sivaprakasam, M and Singh, PR and Bashirullah, RS and Wang, GX}, year={2003}, month={Nov}, pages={986–995} }
 @article{bashirullah_liu_2002, title={Raised cosine approximation signalling technique for reduced simultaneous switching noise}, volume={38}, ISSN={["1350-911X"]}, DOI={10.1049/el:20020852}, abstractNote={A new technique for reducing noise crosstalk due to inductive effects in high-speed switching environments is presented. A signalling scheme based on raised cosine approximation (RCA) pulses is used to achieve gradual buffer turn on without any speed penalties. A new current-mode RCA line driver is proposed and incorporated in a 16 bit 1 Gbit/s off-chip transmitter. Simulation results based on TSMC 0.25 /spl mu/m show ground bounce noise reduction greater than 40%.}, number={21}, journal={ELECTRONICS LETTERS}, author={Bashirullah, R and Liu, W}, year={2002}, month={Oct}, pages={1256–1258} }
 @article{margalit_maia_weiland_greenberg_fujii_torres_piyathaisere_o'hearn_liu_lazzi_et al._2002, title={Retinal prosthesis for the blind}, volume={47}, DOI={10.1016/S0039-6257(02)00311-9}, abstractNote={Most of current concepts for a visual prosthesis are based on neuronal electrical stimulation at different locations along the visual pathways within the central nervous system. The different designs of visual prostheses are named according to their locations (i.e., cortical, optic nerve, subretinal, and epiretinal). Visual loss caused by outer retinal degeneration in diseases such as retinitis pigmentosa or age-related macular degeneration can be reversed by electrical stimulation of the retina or the optic nerve (retinal or optic nerve prostheses, respectively). On the other hand, visual loss caused by inner or whole thickness retinal diseases, eye loss, optic nerve diseases (tumors, ischemia, inflammatory processes etc.), or diseases of the central nervous system (not including diseases of the primary and secondary visual cortices) can be reversed by a cortical visual prosthesis. The intent of this article is to provide an overview of current and future concepts of retinal and optic nerve prostheses. This article will begin with general considerations that are related to all or most of visual prostheses and then concentrate on the retinal and optic nerve designs. The authors believe that the field has grown beyond the scope of a single article so cortical prostheses will be described only because of their direct effect on the concept and technical development of the other prostheses, and this will be done in a more general and historic perspective..}, number={4}, journal={Survey of Ophthalmology}, author={Margalit, E. and Maia, M. and Weiland, J. D. and Greenberg, R. J. and Fujii, G. Y. and Torres, G. and Piyathaisere, D. V. and O'Hearn, T. M. and Liu, W. T. and Lazzi, G. and et al.}, year={2002}, pages={335–356} }
 @article{liu_vichienchom_clements_demarco_hughes_mcgucken_humayun_juan_weiland_greenberg_2000, title={A neuro-stimulus chip with telemetry unit for retinal prosthetic device}, volume={35}, ISSN={["1558-173X"]}, DOI={10.1109/4.871327}, abstractNote={In this retinal prosthesis project, a rehabilitative device is designed to replace the functionality of defective photoreceptors in patients suffering from retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The device consists of an extraocular and an intraocular unit. The implantable component receives power and a data signal via a telemetric inductive link between the two units. The extraocular unit includes a video camera and video processing board, a telemetry protocol encoder chip, and an RF amplifier and primary coil. The intraocular unit consists of a secondary coil, a rectifier and regulator, a retinal chip with a telemetry protocol decoder, a stimulus signal generator, and an electrode array. This paper focuses on the design, fabrication, and testing of a microchip which serves as the telemetry protocol decoder and stimulus signal generator. It is fabricated by MOSIS with 1.2-mm CMOS technology and was demonstrated to provide the desired biphasic current stimulus pulses for an array of 100 retinal electrodes at video frame rates.}, number={10}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={Liu, WT and Vichienchom, K and Clements, M and DeMarco, SC and Hughes, C and McGucken, E and Humayun, MS and Juan, E and Weiland, JD and Greenberg, R}, year={2000}, month={Oct}, pages={1487–1497} }
 @misc{hall_clements_liu_bilbro_2000, title={Integrated circuits having cooperative ring oscillator clock circuits therein to minimize clock skew}, volume={6,104,253}, number={2000 Aug. 15}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Hall, L. C. and Clements, S. M. and Liu, W.-T. and Bilbro, G. L.}, year={2000} }
 @article{hsieh_liu_calvin_2000, title={Integrated parametric timing optimization of digital systems}, volume={19}, ISSN={["0278-0070"]}, DOI={10.1109/43.838997}, abstractNote={Clock skew optimization is a timing technique to improve system performance by employing scheduled skews at flip-flops. The integrated framework presented here includes a new linear programming (LP) formulation for the clock skew optimization problem. In this work, we use the concept of a global time frame, instead of a local one, to find a set of optimal skews to minimize system cycle time. The framework provides a firm theoretical foundation for scheduling skews into existing designs. Furthermore, we extend the LP formulation to accommodate retiming in the optimization process. Our framework allows for concurrent timing optimization of a design by retiming the circuit and scheduling clock skews at flip-flops. It is shown that this optimization can be formulated as a mixed-integer linear program and significantly reduce the clock period.}, number={4}, journal={IEEE TRANSACTIONS ON COMPUTER-AIDED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS}, author={Hsieh, HY and Liu, WT and Calvin, R}, year={2000}, month={Apr}, pages={482–489} }
 @article{bilbro_hall_clements_liu_1999, title={Convolution, deconvolution, and mean field annealing suitable for analog VLSI}, volume={46}, ISSN={["1057-7130"]}, DOI={10.1109/82.752912}, abstractNote={We formulate several standard digital image processing operations as circuits suitable for implementation in real-time analog VLSI, including nonlinear piecewise-constant image restoration using mean field annealing as a global optimization technique. We report test results from an imaging chip that performs user-controlled convolution of the image. We use simulated results for mean field annealing (MFA) in SPICE to show that deconvolution could be implemented by rearranging the subcircuits that perform the corresponding convolution. We report the results of realizing deconvolution in this way on a printed circuit board.}, number={2}, journal={IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-ANALOG AND DIGITAL SIGNAL PROCESSING}, author={Bilbro, GL and Hall, LC and Clements, M and Liu, WT}, year={1999}, month={Feb}, pages={120–128} }
 @article{burleson_ciesielski_klass_liu_1998, title={Wave-pipelining: A tutorial and research survey}, volume={6}, ISSN={["1063-8210"]}, DOI={10.1109/92.711317}, abstractNote={Wave-pipelining is a method of high-performance circuit design which implements pipelining in logic without the use of intermediate latches or registers. The combination of high-performance integrated circuit (IC) technologies, pipelined architectures, and sophisticated computer-aided design (CAD) tools has converted wave-pipelining from a theoretical oddity into a realistic, although challenging, VLSI design method. This paper presents a tutorial of the principles of wave-pipelining and a survey of wave-pipelined VLSI chips and CAD tools for the synthesis and analysis of wave-pipelined circuits.}, number={3}, journal={IEEE TRANSACTIONS ON VERY LARGE SCALE INTEGRATION (VLSI) SYSTEMS}, author={Burleson, WP and Ciesielski, M and Klass, F and Liu, WT}, year={1998}, month={Sep}, pages={464–474} }
 @article{kang_liu_cavin_1997, title={A CMOS high-speed data recovery circuit using the matched delay sampling technique}, volume={32}, ISSN={["0018-9200"]}, DOI={10.1109/4.634670}, abstractNote={This paper presents a scheme and circuitry for demultiplexing and synchronizing high-speed serial data using the matched delay sampling technique. By simultaneously propagating data and clock signals through two different delay taps, the sampler achieves a very fine sampling resolution which is determined by the difference between the data and clock delays. This high resolution sampling capability of the matched delay sampler can be used in the oversampling data recovery circuit. A data recovery circuit using the matched delay sampling technique has been designed and fabricated in 1.2-/spl mu/m CMOS technology. The chip has been tested at 417 Mb/s [2.4 ns nonreturn to zero (NRZ)] input data and demultiplexes serial input data into four 104 Mb/s (9.6 ns NRZ) output streams with 800 mW power consumption at 4 V power supply. While recovering data, the sampling clock running at 1/4 of the data frequency is phase-tracking with the input data based on information extracted from a digital phase control circuit.}, number={10}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={Kang, JK and Liu, WT and Cavin, RK}, year={1997}, month={Oct}, pages={1588–1596} }
 @article{hsieh_liu_franzon_cavin_1997, title={Clocking optimization and distribution in digital systems with scheduled skews}, volume={16}, ISSN={["0922-5773"]}, DOI={10.1023/A:1007934922990}, number={2-3}, journal={JOURNAL OF VLSI SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY}, author={Hsieh, HY and Liu, WT and Franzon, P and Cavin, R}, year={1997}, pages={131–147} }
 @article{yang_schlesser_wolden_liu_davis_sitar_prater_1997, title={Control of diamond heteroepitaxy on nickel by optical reflectance}, volume={70}, ISSN={["0003-6951"]}, DOI={10.1063/1.118756}, abstractNote={Real time in situ laser reflectometry was used to investigate changes in surface morphology observed during the nucleation of oriented diamond on Ni in a hot filament chemical vapor deposition reactor. Characteristic features observed in the intensities of reflected and scattered light were interpreted by comparison with scanning electron micrographs of the diamond seeded substrates quenched at sequential stages of the process. Based on this analysis, a process was developed in which the scattered light signal was used as a steering parameter. Using this process, oriented nucleation and growth of diamond on Ni can be repeatedly achieved.}, number={22}, journal={APPLIED PHYSICS LETTERS}, author={Yang, PC and Schlesser, R and Wolden, CA and Liu, W and Davis, RF and Sitar, Z and Prater, JT}, year={1997}, month={Jun}, pages={2960–2962} }
 @article{moyer_clements_liu_schaffer_cavin_1997, title={The delay vernier pattern generation technique}, volume={32}, ISSN={["0018-9200"]}, DOI={10.1109/4.563677}, abstractNote={The authors describe a new technique for generating an arbitrary digital data stream with very fine timing resolution. Note that this timing resolution specifies the output edge placement precision, not the bit rate. The resolution is determined by the difference between two propagation delays rather than by an absolute delay. Because this difference can be made very small, the circuit, called the delay vernier generator, can achieve unprecedented timing resolution in a particular circuit technology. Also, this very precise timing is obtained without requiring an extremely high speed clock. The generator architecture includes delay-locked loop calibration mechanisms to compensate for process and temperature variations. A prototype chip was fabricated in a 1.2-/spl mu/m CMOS technology, and measurements confirmed that resolutions as fine as 100 ps can be achieved reliably.}, number={4}, journal={IEEE JOURNAL OF SOLID-STATE CIRCUITS}, author={Moyer, GC and Clements, M and Liu, WT and Schaffer, T and Cavin, RK}, year={1997}, month={Apr}, pages={551–562} }