Philipp Dominik Häfliger

• Roy, Avisek; Azadmehr, Mehdi; Häfliger, Philipp; Ta, Bao Quoc & Aasmundtveit, Knut Eilif (2019). Direct Synthesis of Carbon Nanotubes in CMOS-Layout of Micro-heaters. IEEE International Conference on Nanotechnology.  ISSN 1944-9399.  2018-July, s 1- 4 . doi: 10.1109/NANO.2018.8626363 Vis sammendrag

  Direct integration of Carbon Nanotubes (CNTs) in CMOS is important for commercially manufacturing low-cost CNT-based sensors. In such compact sensors, CNTs would act as sensing element, and CMOS circuits would process relevant signals from the CNTs. CNTs can be directly synthesized and integrated into CMOS by local thermal chemical vapor deposition (CVD), where a hot spot of 900 °C can be generated by CMOS micro-heaters. However, a sufficient thermal gradient between the micro-heaters and nearest CMOS devices is a prerequisite to ensure non-destructive temperature (<300 °C) in the electronic circuit regions. Our previous works have shown modelling and simulation of various CMOS micro-heaters that are promising for fulfilling these temperature requirements. In this paper, we investigate the layout designs of different metal and polysilicon micro-heaters using AMS 0.35μm CMOS process. Optical micrographs of the fabricated micro-heaters are also presented.

• Roy, Avisek; Azadmehr, Mehdi; Ta, Bao Quoc; Häfliger, Philipp & Aasmundtveit, Knut (2019). Design and fabrication of CMOS microstructures to locally synthesize carbon nanotubes for gas sensing. Sensors.  ISSN 1424-8220.  19(19) . doi: 10.3390/s19194340 Vis sammendrag

  Carbon nanotubes (CNTs) can be grown locally on custom-designed CMOS microstructures to use them as a sensing material for manufacturing low-cost gas sensors, where CMOS readout circuits are directly integrated. Such a local CNT synthesis process using thermal chemical vapor deposition (CVD) requires temperatures near 900 °C, which is destructive for CMOS circuits. Therefore, it is necessary to ensure a high thermal gradient around the CNT growth structures to maintain CMOS-compatible temperature (below 300 °C) on the bulk part of the chip, where readout circuits are placed. This paper presents several promising designs of CNT growth microstructures and their thermomechanical analyses (by ANSYS Multiphysics software) to check the feasibility of local CNT synthesis in CMOS. Standard CMOS processes have several conductive interconnecting metal and polysilicon layers, both being suitable to serve as microheaters for local resistive heating to achieve the CNT growth temperature. Most of these microheaters need to be partially or fully suspended to produce the required thermal isolation for CMOS compatibility. Necessary CMOS post-processing steps to realize CNT growth structures are discussed. Layout designs of the microstructures, along with some of the microstructures fabricated in a standard AMS 350 nm CMOS process, are also presented in this paper.

• Buccino, Alessio Paolo; Hagen, Espen; Einevoll, Gaute; Häfliger, Philipp & Cauwenberghs, Gert (2018). Independent Component Analysis for Fully Automated Multi-Electrode Array Spike Sorting, In Nigel Lovell (ed.),  Annual Conference of the IEEE Engineering in Medicine and Biology Society.  IEEE conference proceedings.  ISBN 9781538636473.  paper.  s 2627 - 2630
• Buccino, Alessio Paolo; Kordovan, Michael; Ness, Torbjørn V; Merkt, Benjamin; Häfliger, Philipp; Fyhn, Marianne; Cauwenberghs, Gert; Rotter, Stefan & Einevoll, Gaute (2018). Combining biophysical modeling and deep learning for multielectrode array neuron localization and classification. Journal of Neurophysiology.  ISSN 0022-3077.  120(3), s 1212- 1232 . doi: 10.1152/jn.00210.2018 Fulltekst i vitenarkiv.
• Buccino, Alessio Paolo; Lepperød, Mikkel Elle; Dragly, Svenn-Arne; Häfliger, Philipp; Fyhn, Marianne & Hafting, Torkel (2018). Open source modules for tracking animal behavior and closed-loop stimulation based on Open Ephys and Bonsai. Journal of Neural Engineering.  ISSN 1741-2560.  15, s 1- 12 . doi: 10.1088/1741-2552/aacf45 Fulltekst i vitenarkiv.
• Buccino, Alessio Paolo; Ness, Torbjørn V; Einevoll, Gaute; Cauwenberghs, Gert & Häfliger, Philipp (2018). A Deep Learning Approach for the Classification of Neuronal Cell Types, In Nigel Lovell (ed.),  Annual Conference of the IEEE Engineering in Medicine and Biology Society.  IEEE conference proceedings.  ISBN 9781538636473.  paper.  s 999 - 1002
• Farian, Lukasz; Bardallo, Juan Antonio Lenero & Häfliger, Philipp (2018). Live Demonstration: A Miniaturized Two-Axis Low Latency and Low-Power Sun Sensor for Attitude Determination of Sounding Rockets, In Gianluca Setti & Franco Maloberti (ed.),  International Symposium on Circuits and Systems.  IEEE conference proceedings.  ISBN 9781538648827.  live demonstration.
• Farian, Lukasz; Häfliger, Philipp & Leñero-Bardallo, Juan Antonio (2018). A Miniaturized Two-Axis Ultra Low Latency and Low-Power Sun Sensor for Attitude Determination of Micro Space Probes. IEEE Transactions on Circuits and Systems Part 1: Regular Papers.  ISSN 1549-8328.  65(5), s 1543- 1554 . doi: 10.1109/TCSI.2017.2763990
• Buccino, Alessio Paolo; Ness, Torbjørn Vefferstad; Einevoll, Gaute; Cauwenberghs, Gert & Häfliger, Philipp (2017). Localizing neuronal somata from Multi-Electrode Array in-vivo recordings using deep learning. IEEE Engineering in Medicine and Biology Society. Conference Proceedings.  ISSN 1557-170X.  s 974- 977 . doi: 10.1109/EMBC.2017.8036988 Fulltekst i vitenarkiv. Vis sammendrag

  With the latest development in the design and fabrication of high-density Multi-Electrode Arrays (MEA) for in-vivo neural recordings, the spatiotemporal information in the recorded signals allows for refined estimation of a neuron’s location around the probe. In parallel, advances in computational models for neural activity enables simulation of recordings from neurons with detailed morphology. Our approach uses deep learning algorithms on a large set of such simulation data to extract the 3D position of the neuronal somata. Multi-compartment models from 13 different neural morphologies in layer 5 (L5) of the rat’s neocortex are placed at random locations and with different alignments with respect to the MEA. The sodium trough and repolarisation peak images on the MEA serve as input features for a Convolutional Neural Network (CNN), which predicts the neural location robustly and with low error rates. The forward modeling/machine learning approach yields very accurate results for the different morphologies and is able to cope with different neuron alignments.

• Greco, Jordan A.; Fernandes, Andre Lourenco; Wagner, Nicole L.; Azadmehr, Mehdi; Häfliger, Philipp; Johannessen, Erik Andrew & Birge, Robert R. (2017). Pixel characterization of a protein-based retinal implant using a microfabricated sensor array. International Journal of High Speed Electronics and Systems.  ISSN 0129-1564.  26(3), s 1- 20 . doi: 10.1142/S0129156417400122
• Fernandes, Andre Lourenco; Azadmehr, Mehdi; Johannessen, Erik Andrew & Häfliger, Philipp (2016). An osmotic pressure sensor for monitoring the level of hydration in biological fluids. IEEE Sensors Journal.  ISSN 1530-437X.  16(11), s 4331- 4337 . doi: 10.1109/JSEN.2016.2548361 Vis sammendrag

  A miniaturized hydration sensor that records the electrolyte balance in biological fluids and that translates this quantity into an osmotic pressure signal has been developed. The sensor measures 16 mm x 8 mm and integrates a semipermeable membrane, a piezoresistive pressure transducer, and an electronic readout platform. The dynamic measurement range of 220-340 mOsm L-1 (280 ± 60 mOsm L-1) covers a serious state of dehydration to a serious state of overhydration (represented by a Ahydration = ±20%). Ion exchange membranes were found to be the best candidates for integration with the hydration sensor. Reverse osmosis membranes with physical pores (zero Da molecular cutoff) had high ionic leakage rates, in contrast to gas permeable membranes, which proved to be almost impermeable to water vapor. Consequently, the use of a Nafion NR211 membrane facilitated a sensor response with a time constant of 2.5 h, which conforms to the slow change in osmotic pressure associated with hydration. The low-power front-end circuit architecture is based on an analog pressure-to-frequency converter, consuming only 39.4 μW, and capable of recording changes in hydration with a resolution of 5.71 bits (ENOBSNR). The small size of the sensor components, combined with the interface low-power architecture, renders it suitable for further miniaturization required for implantation into the human body.

• Häfliger, Philipp; Nabovati, G.; Sawan, M.; Wagner, N.; Greco, J. & Birge, R. R. (2016). Combined optical and chemical asynchronous event pixel array. Proceedings - IEEE International Symposium on Cicuits and Systems.  ISSN 0271-4310.  2016-July, s 317- 320 . doi: 10.1109/ISCAS.2016.7527234
• Leñero Bardallo, Juan Antonio; Häfliger, Philipp; Carmona-Galán, R. & Rodríguez-Vázquez, Angel (2016). A Bio-Inspired Vision Sensor With Dual Operation and Readout Modes. IEEE Sensors Journal.  ISSN 1530-437X.  16(2), s 317- 330 . doi: 10.1109/JSEN.2015.2483898
• Farian, Lukasz; Häfliger, Philipp & Bardallo, Juan Antonio Lenero (2015). Miniaturized Sun sensor with in-pixel processing for Attitude Determination of micro space probes, In Jorge Fernandes & Wouter Serdjin (ed.),  Proceedings of the IEEE International Symposium on Circuits and Systems.  IEEE conference proceedings.  ISBN 9781479983926.  paper.
• Farian, Lukasz; Leñero-Bardallo, Juan Antonio & Häfliger, Philipp (2015). A Bio-Inspired AER Temporal Tri-Color Differentiator Pixel Array. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  9(5), s 686- 698 . doi: 10.1109/TBCAS.2015.2492460
• Lee, Kin Keung; Lande, Tor Sverre & Häfliger, Philipp (2015). A sub-µW bandgap reference circuit with an inherent curvature-compensation property. IEEE Transactions on Circuits and Systems Part 1: Regular Papers.  ISSN 1549-8328.  62(1), s 1- 9 . doi: 10.1109/TCSI.2014.2340553 Vis sammendrag

  A new current-mode bandgap reference circuit (BGR) which is capable of generating sub-1-V output voltage is presented. It has not only the lowest theoretical minimum current consumption among published current-mode BGRs, but also additional advantages of an inherent curvature-compensation function and not requiring NPN BJTs. The curvature-compensation is achieved by utilizing the exponential behavior of sub-threshold CMOS transistors to compensate the BJT base-emitter voltage high-order temperature dependence. By taking advantages of the continuing development of CMOS technology, sub-µW power consumption is achieved with a reasonable core area. Related design considerations and challenges are discussed and analyzed. The proposed BGR is realized in a TSMC 90 nm process. Measurement results shows a temperature coefficient without trimming as low as 10.1 ppm/°C over a temperature range of 70°C because of the proposed curvature-compensation technique. The average value is 32.6 ppm/°C which could be improved by trimming resistor ratios. The average power consumption at room temperature is 576 nW, with a core area of only 0.028 mm².

• Nguyen, Thanh Trung & Häfliger, Philipp (2015). A Sub-micro Watt Implantable Capacitive Sensor System for Biomedical Applications. IEEE Transactions on Circuits and Systems - II - Express Briefs.  ISSN 1549-7747.  62(2), s 209- 213 . doi: 10.1109/TCSII.2014.2368260 Vis sammendrag

  This paper presents a sub-micro Watt, offset-free and implantable system for a biomedical capacitive sensor. The system is powered by a 13.56-MHz radio frequency (RF) signal and performs sensor signal amplification, analog-to-digital conversion (ADC) and load-shift keying (LSK) uplink data transmission within 640 µs. An ultra-low-power capacitance-to-digital converter (CDC) is designed by replacing a power hungry operational amplifier (Opamp) with a subthreshold inverter in a switched-capacitor amplifier (SC-amp). A fast response gain compensation method is employed to reduce the gain error of the SC-amp while achieving a high energy efficiency for the CDC. To eliminate the offset, a two-step auto calibration is applied. The application-specific integrated circuit (ASIC) is implemented in the TSMC 90-nm CMOS technology and the whole system achieves an 8.02 effective number of bits (ENOB) with 9-bit linearity while consuming only 5.5 µW.

• Zaher, Ali; Særsten, Joar D; Nguyen, Thanh Trung & Häfliger, Philipp (2015). Integrated electronic system for implantable sensory NFC tag, In  37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC).  IEEE conference proceedings.  ISBN 978-1-4244-9271-8.  paper.  s 7119 - 7122
• Farian, Lukasz; Leñero-Bardallo, Juan Antonio & Häfliger, Philipp (2014). A bio-inspired AER temporal tri-color differentiator, In  Biomedical Circuits and Systems Conference (BioCAS), 2014 IEEE.  IEEE conference proceedings.  ISBN 978-1-4799-2346-5.  paper.  s 524 - 527
• Fernandes, Andre Lourenco; Azadmehr, Mehdi; Johannessen, Erik Andrew & Häfliger, Philipp (2014). Low power integrated electronics system for the operation of a miniaturized hydration sensor, In  2014 IEEE 12th International New Circuits and Systems Conference (NEWCAS).  IEEE conference proceedings.  ISBN 978-1-4799-4885-7.  Paper.  s 17 - 20 Vis sammendrag

  The application of MEMS devices with integrated electronics are paving the way for a new generation of miniaturized biomedical sensors with the potential of monitoring physiological parameters in the body. This article presents an application-specific integrated circuit (ASIC) that has been designed for integration in a biomedical sensor capable of detecting events associated with the dehydration and overhydration in the body and presents measurement results from a sensor prototype. The sensor converts the hydration level into an osmotic pressure which in turn is translated into a frequency modulated asynchronous digital signal with a 5.71 bit resolution (ENOB). The ASIC was designed and fabricated using the TSMC90nm CMOS processing technology and is based on a low power architecture with a simulated power consumption of 39.4 μW. The circuit layout has a footprint of 565×265 μm2 and the linear temperature dependent node of the voltage bandgap reference is used to monitor the temperature.

• Leñero-Bardallo, Juan Antonio; Bryn, Dag Halfdan & Häfliger, Philipp (2014). Bio-inspired asynchronous pixel event tricolor vision sensor. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  8(3), s 345- 357 . doi: 10.1109/TBCAS.2013.2271382
• Leñero-Bardallo, Juan Antonio & Häfliger, Philipp (2014). A dual-operation-mode bio-inspired pixel. IEEE Transactions on Circuits and Systems - II - Express Briefs.  ISSN 1549-7747.  61(11), s 855- 859 . doi: 10.1109/TCSII.2014.2350352
• Nguyen, Thanh Trung; Fernandes, Andre Lourenco & Häfliger, Philipp (2014). An energy-efficient implantable transponder for biomedical piezo-resistance pressure sensors. IEEE Sensors Journal.  ISSN 1530-437X.  14(6), s 1836- 1843 . doi: 10.1109/JSEN.2014.2304566
• Nguyen, Thanh Trung & Häfliger, Philipp (2014). A 9.4-bit, 28.8-mV Range Inverter Based Readout Circuit for Implantable Pressure Bridge Piezo-resistive Sensor, In  International Symposium on Circuits and Systems (ISCAS), 2014 IEEE.  IEEE conference proceedings.  ISBN 978-1-4799-3431-7.  Circuits for Bio-sensing.  s 2377 - 2380 Vis sammendrag

  This paper presents an energy efficient inverter based readout circuit for implantable pressure bridge piezo-resistive sensor which can achieve 9 bit resolution with 28.8-mV input voltage range. Only one bridge branch is utilized with interchanging supply voltage to achieve net differential input voltage range, hence reducing the power consumption by a half. A gain compensated technique is applied for inverter based switched capacitor amplifier to achieve both power efficiency and high resolution. A two-step auto calibration is applied to eliminate the offset from non-ideal effects of the switched-capacitor amplifier (SC-amp) and comparator delay. The readout system is implemented and simulated in TSMC 90 nm CMOS technology. With supply voltage of 1.2 V, simulation results show that the circuit can achieve 9.4 bit resolution while consuming only 35 µW during 320 µs conversion time. The digital output code has little sensitivity to temperature variation.

• Nguyen, Thanh Trung; Häfliger, Philipp; Tao, Feng & Chakrabartty, Shantanu (2014). Hybrid CMOS Rectifier based on Synergistic RF-Piezoelectric Energy Scavenging. IEEE Transactions on Circuits and Systems Part 1: Regular Papers.  ISSN 1549-8328.  61(12), s 3330- 3338 . doi: 10.1109/TCSI.2014.2334972
• Zaher, Ali; Häfliger, Philipp; Carrara, Sandro; Puppo, Francesca & De Micheli, Giovanni (2014). Novel Readout Circuit for Memristive Biosensors in Cancer Detection, In  Biomedical Circuits and Systems Conference (BioCAS), 2014 IEEE.  IEEE conference proceedings.  ISBN 978-1-4799-2346-5.  134.  s 448 - 451
• Bryn, Dag Halfdan; Häfliger, Philipp & Leñero-Bardallo, Juan Antonio (2013). Bio-Inspired Asynchronous Pixel Event Tricolor Vision Sensor. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545. . doi: 10.1109/TBCAS.2013.2271382
• Fernandes, Andre Lourenco; Häfliger, Philipp; Azadmehr, Mehdi & Johannessen, Erik (2013). Design and characterization of an osmotic sensor for the detection of events associated with dehydration and overhydration. IEEE Journal of Translational Engineering in Health and Medicine.  ISSN 2168-2372.  1 . doi: 10.1109/JTEHM.2013.2279105 Vis sammendrag

  The level of hydration in the human body is carefully adjusted to control the electrolyte balance that governs the biochemical processes that sustain life. An electrolyte deficiency caused by de- or overhydration will not only limit human performance, but can also lead to serious health problems and death if left untreated. Because humans can withstand a change in hydration of only ±20%, frequent monitoring should be performed in risk groups. This paper presents an osmotic hydration sensor that can record the level of hydration as a function of osmotic pressure in phosphate buffered saline or sodium-chloride solutions that simulate the interstitial fluid in the body. The osmotic pressure is recorded with the aid of an ion-exchange membrane that facilitates the migration of water and cations, in favor of reverse osmosis or gas separation membranes. The hydration sensor is designed to be coupled to an inductively powered readout circuit designed for integration in a micro-implant that has previously been shown to consume only 76 μW of power. The dynamic range spans a state of serious overhydration (220 mOsm L-1) to a serious state of dehydration (340 mOsm L-1) with a response time of ~ 7 h (for a variation of hydration of 20%).

• Häfliger, Philipp & Leñero-Bardallo, Juan Antonio (2013). A dual operation mode bio-inspired vision sensor, In Wouter A. Serdijn (ed.),  Proceedings of the IEEE conference on Biomedical Circuits and Systems.  IEEE conference proceedings.  ISBN 9781479914708.  paper.
• Leñero-Bardallo, Juan Antonio; Bryn, Dag Halfdan & Häfliger, Philipp (2013). Flame monitoring with an AER color vision sensor, In Chang Wen Chen; Wen Gao & Joos Vandewalle (ed.),  2013 IEEE International Symposium on Circuits and Systems (ISCAS).  IEEE conference proceedings.  ISBN 978-1-4673-5760-9.  paper.  s 2404 - 2407
• Nguyen, Thanh Trung & Häfliger, Philipp (2013). An energy efficient inverter based readout circuit for capacitive sensor, In Firat Yazicioglu (ed.),  Biomedical Circuits and Systems Conference (BioCAS), 2013 IEEE.  IEEE conference proceedings.  ISBN 978-1-4799-1469-2.  chapter.  s 326 - 329
• Nguyen, Thanh Trung & Häfliger, Philipp (2013). An energy-efficient implant transponder for continuous glucose monitoring, In  Advanced Technologies for Communications (ATC), 2013 International Conference on.  IEEE conference proceedings.  ISBN 978-1-4799-1086-1.  chapter.  s 345 - 350
• Zaher, Ali & Häfliger, Philipp (2013). Single poly non-volatile memory cells for miniaturized sensors in 90nm CMOS technology, In Ivan Ring Nielsen (ed.),  Proceedings of NORCHIP.  IEEE conference proceedings.  ISBN 978-1-4799-1647-4.  paper.
• Leñero-Bardallo, Juan Antonio; Bryn, Dag Halfdan & Häfliger, Philipp (2012). Live Demonstration: A Bio-inspired Asynchronous Pixel Event Tri-color Vision Sensor. IEEE International Symposium on Circuits and Systems proceedings.  ISSN 0271-4302.  s 726- 726
• Leñero-Bardallo, Juan Antonio; Bryn, Dag Halfdan & Häfliger, Philipp (2012). Live demonstration: A bio-inspired asynchronous pixel event tri-color vision sensor, In  IEEE International Symposium on Circuits and Systems.  IEEE Press.  ISBN 978-1-4673-0219-7.  arikkel.  s 726 - 726
• Nguyen, Thanh Trung & Häfliger, Philipp (2012). Inverter Based Readout Circuit for Implanted Glucose Sensor, In Huang-Te Li; Hsiang-Cheh Huang & Kea-Tiong Tang (ed.),  Biomedical Circuits and Systems Conference (BioCAS), 2012 IEEE.  IEEE conference proceedings.  ISBN 978-1-4673-2293-5.  KAPITTEL.  s 252 - 255
• Trung, NT & Häfliger, Philipp (2012). Inverter Based Readout Circuit for Implanted Glucose Sensor. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  s 252- 255
• Drazen, David Adam; Lichtsteiner, Patrick; Häfliger, Philipp; Delbrück, Tobi & Jensen, Atle (2011). Toward real-time particle tracking using an event-based dynamic vision sensor. Experiments in Fluids.  ISSN 0723-4864.  51(5), s 1465- 1469 . doi: 10.1007/s00348-011-1207-y
• Indiveri, Giacomo; Linares-Barranco, Bernabé; Hamilton, Tara Julia; van Schaik, André; Etienne-Cummings, Ralph; Delbrück, Tobi; Liu, Shi-Chii; Dudek, Piotr; Häfliger, Philipp; Renaud, Sylvie; Schemmel, Johannes; Cauwenberghs, Gert; Arthur, John; Hynna, Kai; Folowosele, Fopefolu; Saighi, Sylvain; Serrano-Gotarredona, Teresa; Wijekoon, Jayawan; Wang, Yingxue & Boahen, Kwabena (2011). Neuromorphic silicon neuron circuits. Frontiers in Neuroscience.  ISSN 1662-4548.  5 . doi: 10.3389/fnins.2011.00073
• Nguyen, Thanh Trung & Häfliger, Philipp (2011). 250Mb/s to 3Gb/s unilateral continuous rate CDR using precise frequency detector and 1/5-rate linear phase detector, In Marcelo Lubaszewski; ISCAS IEEE (ed.),  Proc. 2011 IEEE International Symposium on Circuits and Systems.  IEEE conference proceedings.  ISBN 978-1-4244-9472-9.  10.1109/ISCAS.2011.5937531.  s 181 - 184
• Nguyen, Thanh Trung & Häfliger, Philipp (2011). Time domain ADC for blood glucose implant. Electronics Letters.  ISSN 0013-5194.  47(26), s S18- S20 . doi: 10.1049/el.2011.2685
• Häfliger, Philipp (2010). Live demonstration: inductive power and telemetry for micro-implant. IEEE International Symposium on Circuits and Systems proceedings.  ISSN 0271-4302.  s 2775- 2775
• Häfliger, Philipp (2010). Live demonstration: inductive power and telemetry for micro-implant, In Amara Amara (ed.),  Proceedings of the IEEE international symposium on circuits and systems 2010.  IEEE conference proceedings.  ISBN 978-1-4244-5309-2.  live demonstration description.  s 2775 - 2775
• Johannessen, Erik; Krushinitskaya, Olga; Sokolov, Andrey; Häfliger, Philipp; Hoogerwerf, Arno; Hinderling, Christian; Kautio, Kari; Lenkkeri, Jaakko; Strömmer, Esko; Kondratyev, Vasily; Tønnessen, Tor Inge; Mollnes, Tom Eirik; Jakobsen, Henrik; Zimmer, Even & Akselsen, Bengt (2010). Toward an injectable continuous osmotic glucose sensor. Journal of Diabetes Science and Technology.  ISSN 1932-2968.  4(4), s 882- 892 Vis sammendrag

  BACKGROUND: The growing pandemic of diabetes mellitus places a stringent social and economic burden on the society. A tight glycemic control circumvents the detrimental effects, but the prerogative is the development of new more effective tools capable of longterm tracking of blood glucose (BG) in vivo. Such discontinuous sensor technologies will benefit from an unprecedented marked potential as well as reducing the current life expectancy gap of eight years as part of a therapeutic regime. METHOD: A sensor technology based on osmotic pressure incorporates a reversible competitive affinity assay performing glucose-specific recognition. An absolute change in particles generates a pressure that is proportional to the glucose concentration. An integrated pressure transducer and components developed from the silicon micro- and nanofabrication industry translate this pressure into BG data. RESULTS: An in vitro model based on a 3.6 x 8.7 mm large pill-shaped implant is equipped with a nanoporous membrane holding 4-6 nm large pores. The affinity assay offers a dynamic range of 36-720 mg/dl with a resolution of +/-16 mg/dl. An integrated 1 x 1 mm(2) large control chip samples the sensor signals for data processing and transmission back to the reader at a total power consumption of 76 microW. CONCLUSIONS: Current studies have demonstrated the design, layout, and performance of a prototype osmotic sensor in vitro using an affinity assay solution for up to four weeks. The small physical size conforms to an injectable device, forming the basis of a conceptual monitor that offers a tight glycemic control of BG. 2010 Diabetes Technology Society.

• Krushinitskaya, Olga; Häfliger, Philipp; Vinsand, Tormod; Tønnessen, Tor Inge; Jakobsen, Henrik & Johannessen, Erik A. (2009). Novel Osmotic Sensor for a Continuous Implantable Blood-Sugar Reader, In . NN (ed.),  6th International Workshop on Wearable Micro and Nano Technologies for Personalized Health (pHealth).  IEEE conference proceedings.  ISBN 978-1-4244-5252-1.  Paper.  s 25 - 28 Vis sammendrag

  This paper presents the design and development of a novel osmotic glucose sensor that will be miniaturized to record the concentration of blood sugar in people suffering from diabetes mellitus. Key sensor components based on microfabrication technologies include a 1.03 bar differential silicon pressure transducer, nanoporous membrane and a 2 μW electronic interface combined with a wireless inductive powered communication link running at 13.56 MHz. The verification of the components and design principle in situ has permitted the detection of osmotic pressures from 0 to 40 mM glucose based on the direct measurements of glucose and the implementation of a reversible competitive affinity assay. The sensor components will be translated into a miniaturized package suitable for subcutaneous implantation.

• Olsson, Jenny Anna Maria & Häfliger, Philipp (2009). Live demonstration of an asynchronous integrate-and-fire pixel-event vision sensor, In  Proceedings of the 2009 IEEE International Symposium on Circuits and Systems.  IEEE conference proceedings.  ISBN 978-1-4244-3828-0.  article.  s 774
• Serrano-Gotarredona, R; Oster, M; Lichtsteiner, P; Linares-Barranco, A; Paz-Vicente, R; Gomez-Rodriguez, F; Camunas-Mesa, L; Berner, R; Rivas-Perez, M; Delbruck, T; Liu, SC; Douglas, R; Häfliger, Philipp; Jimenez-Moreno, G; Ballcels, AC; Serrano-Gotarredona, T; Acosta-Jimenez, AJ & Linares-Barranco, B (2009). CAVIAR: A 45k Neuron, 5M Synapse, 12G Connects/s AER Hardware Sensory-Processing-Learning-Actuating System for High-Speed Visual Object Recognition and Tracking. IEEE Transactions on Neural Networks.  ISSN 1045-9227.  20(9), s 1417- 1438 . doi: 10.1109/TNN.2009.2023653
• Berge, Hans K. Otnes & Häfliger, Philipp (2008). A Gate Leakage Feedback Element in an Adaptive Amplifier Application. IEEE transactions on circuits and systems - 2, Analog and digital signal processing.  ISSN 1057-7130.  55, s 101- 105 . doi: 10.1109/TCSII.2007.910761 Vis sammendrag

  This brief presents a method to exploit gate leakage (GL) to create a feedback element for an input offset insensitive and output offset programmable inverting amplifier. Measurements are shown from a test circuit produced in a 90-nm multithreshold CMOS process where a GL element uses thin oxide and a amplifier input stage uses thick oxide. The feedback element has very high nonlinear impedance from about 100 MOhm to several GOhm depending on the applied voltage, and is suitable for adaptive applications where long time constants (1 ms to 1s) are required and small, slowly wandering offsets can be tolerated.

• Häfliger, Philipp & Johannessen, Erik (2008). Analog to Interval Encoder with Active Use of Gate Leakage for an Implanted Blood-Sugar Sensor, In Andreas Andreou (ed.),  Proceedings of the IEEE Biomedical Circuits and Systems Conference.  IEEE conference proceedings.  ISBN 1-4244-1525-X.  artikkel.
• Olsson, Jenny Anna Maria & Häfliger, Philipp (2008). Mismatch reduction with relative reset in integrate-and-fire photo-pixel array, In Andreas Andreou (ed.),  Proceedings of the IEEE Biomedical Circuits and Systems Conference.  IEEE conference proceedings.  ISBN 1-4244-1525-X.  artikkel.
• Olsson, Jenny Anna Maria & Häfliger, Philipp (2008). Two Color Asynchronous Event Photo Pixel, In David Allstot & Mani Soma (ed.),  Proceeding of the IEEE International Symposium on Circuits and Systems.  IEEE conference proceedings.  ISBN 978-1-4244-1683-7.  Article.  s 2146 - 2149
• Berge, Hans K. Otnes & Häfliger, Philipp (2007). High-Speed Serial AER on FPGA, In Nam Ling & Gianluca Setti (ed.),  Circuits and Systems, 2007. ISCAS 2007. IEEE International Symposium on.  IEEE conference proceedings.  ISBN 1-4244-0921-7.  A4L-G.5 in SPECIAL SESSION: Spike Processing Based Hardware Vision Systems.  s 857 - 860
• Häfliger, Philipp (2007). Adaptive WTA with an analog VLSI neuromorphic learning chip. IEEE Transactions on Neural Networks.  ISSN 1045-9227.  18(2), s 551- 572 . doi: 10.1109/TNN.2006.884676
• Häfliger, Philipp & Berge, Hans K. Otnes (2007). Exploiting Gate Leakage in Deep Submicrometer CMOS for Input Offset Adaptation. IEEE transactions on circuits and systems - 2, Analog and digital signal processing.  ISSN 1057-7130.  54(2), s 127- 130
• Serrano-Gotarredona, R.; Oster, Matthias; Häfliger, Philipp & Riis, Håvard Kolle (2006). AER Building Blocks for Multi-Layer Multi-Chip Neuromorphic Vision Systems, In Yair Weiss; Bernhard Schölkopf & John Platt (ed.),  Advances in Neural Information Processing Systems.  MIT Press.  ISBN 0-262-19534-8.  artikkel.
• Azadmehr, Mehdi & Häfliger, Philipp (2005). A foveated AER imager chip, In Nobuo Fujii (ed.),  Proceedings of the IEEE international symposium on circuits and systems 2005.  IEEE conference proceedings.  ISBN 0-7803-8834-8.  article.  s 2751 - 2754
• Riis, Håvard Kolle & Häfliger, Philipp (2005). An asynchronous 4-to-4 AER mapper. Lecture Notes in Computer Science (LNCS).  ISSN 0302-9743.  3512, s 494- 501 Vis sammendrag

  In this paper a fully functional prototype of an asynchronous 4-to-4 Address Event Representation (AER) mapper is presented. AER is an event driven communication protocol originally used in VLSI implementations of neural networks to transfer action potentials between neurons. Often, this protocol is used for direct inter-chip communication between neuromorphic chips containing assemblies of neurons. Without an active device in between two such chips, the network connections between them are hard-wired in the chip design. More fexibility can be achieved by communicating through an AER mapper: The network can be freely configured and, furthermore, several AER busses can be merged and splitted to form a complex network structure. We present here an asynchronous AER mapper which offers an easy and versatile solution. The AER mapper receives input from four different AER busses and redirects the input AE to four output AER busses. The control circuitry is implemented on a FPGA and is fully asynchronous, and pipelining is used to maximize throughput. The mapping is performed according to preprogrammed lookup tables, which is stored on external RAM. The mapper can emulate a network of up to 2^19 direct connections and test results show that the mapper can handle as much as 30x10^6 events/second.

• Häfliger, Philipp (2004). On using the time domain for analog signal representation in electronic circuits. Neuromorphic Engineer Newsletter.  1(1)
• Häfliger, Philipp Dominik & Jørgensen Aasebø, Elin (2004). A rank encoder: Adaptive analog to digital conversion exploiting time domain spike signal processing. Analog Integrated Circuits and Signal Processing.  ISSN 0925-1030.  40(1), s 39- 51

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• Roy, Avisek; Azadmehr, Mehdi; Häfliger, Philipp; Ta, Bao Quoc & Aasmundtveit, Knut Eilif (2018). Direct Synthesis of Carbon Nanotubes in CMOS-Layout of Micro-heaters.
• Buccino, Alessio Paolo; Ness, Torbjørn Vefferstad; Einevoll, Gaute; Cauwenberghs, Gert; Fyhn, Marianne; Hafting, Torkel & Häfliger, Philipp (2017). Classification of Neural Cell-types from Extracellular Signatures on Multi-Electrode Arrays using Deep Learning.
• Häfliger, Philipp; Chakrabartty, Shantanu & Wang, Z. (2017). Guest Editorial ISCAS 2016 Special Issue. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  11(5), s 977- 978 . doi: 10.1109/TBCAS.2017.2746538
• Subbarao, Girish Aramanekoppa & Häfliger, Philipp (2017). Fair Arbitration for Multi-Instrument Space Probe.
• Buccino, Alessio Paolo; Stöber, Tristan Manfred; Næss, Solveig; Cauwenberghs, Gert & Häfliger, Philipp (2016). Extracellular single neuron stimulation with high-density multi-electrode array.
• Di Bernardo, Mario; Barros Da Silva, Eduardo Antonio; Häfliger, Philipp & Setti, Gianluca (2016). Guest Editorial Special Section on the 2015 IEEE International Symposium on Circuits and Systems (ISCAS 2015). IEEE Transactions on Circuits and Systems Part 1: Regular Papers.  ISSN 1549-8328.  63(5), s 565- 566 . doi: 10.1109/TCSI.2016.2557578
• Farian, Lukasz; Leñero-Bardallo, Juan Antonio & Häfliger, Philipp (2014). Live Demonstration: A Bio-Inspired AER Temporal Tri-Color Differentiator.
• Fernandes, Andre Lourenco; Johannessen, Erik; Azadmehr, Mehdi & Häfliger, Philipp (2014). Low power integrated electronics system for the operation of a miniaturized hydration sensor. Vis sammendrag

  The application of MEMS devices with integrated electronics are paving the way for a new generation of miniaturized biomedical sensors with the potential of monitoring physiological parameters in the body. This article presents an application-specific integrated circuit (ASIC) that has been designed for integration in a biomedical sensor capable of detecting events associated with the dehydration and overhydration in the body and presents measurement results from a sensor prototype. The sensor converts the hydration level into an osmotic pressure which in turn is translated into a frequency modulated asynchronous digital signal with a 5.71 bit resolution (ENOB). The ASIC was designed and fabricated using the TSMC90nm CMOS processing technology and is based on a low power architecture with a simulated power consumption of 39.4 μW. The circuit layout has a footprint of 565×265 μm^2 and the linear temperature dependent node of the voltage bandgap reference is used to monitor the temperature.

• Zaher, Ali; Häfliger, Philipp; Puppo, Francesca; De Micheli, Giovanni & Carrara, Sandro (2014). Novel Readout Circuit for Memristive Cancer Detection Sensors.
• Jung, Tzyy-Ping & Häfliger, Philipp (2013). Guest Editorial—Special Issue on Selected Papers From BioCAS 2012. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  7(4), s 561- 562 . doi: 10.1109/TBCAS.2013.2283649
• Jung, Tzyy-Ping & Häfliger, Philipp (2013). Special Issue on Selected Papers From BioCAS 2012. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  7(5), s 561- 562 . doi: 10.1109/TBCAS.2013.2283649
• Langmyhr, Dag & Häfliger, Philipp (2013). Computer architecture -- compendium for INF2270.
• Zaher, Ali & Häfliger, Philipp (2013). Single poly non-volatile memory cells for miniaturized sensors in 90nm CMOS technology.
• Chang, Joseph; Wong, Stephen; Newcomb, Robert & Häfliger, Philipp (2012). The Third Revolution in Medicine-the Convergence of Life Sciences with Physical Sciences, Mathematics, and ENGINEERING. IEEE Transactions on Circuits and Systems.  ISSN 0098-4094.  12(3), s 4- 7 . doi: 10.1109/MCAS.2012.2206989
• Constandinou, T & Häfliger, Philipp (2012). Guest Editorial-Special Issue on Selected Papers From BioCAS 2011. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  6(5), s 401- 402 . doi: 10.1109/TBCAS.2012.2226072
• Fernandes, Andre Lourenco; Häfliger, Philipp; Azadmehr, Mehdi & Johannessen, Erik (2012). Design and characterization of an osmotic sensor for the detection of events associated with dehydration and overhydration. Vis sammendrag

  The level of hydration in the human body is carefully adjusted to control the electrolyte balance that governs the biochemical processes that sustain life. An electrolyte deficiency caused by de- or overhydration will not only limit the performance of say an athlete, or a professional, but lead to serious health problems and death if left untreated. Since humans can withstand a change in hydration of only +/-20%, frequent monitoring should be performed in risk groups. This article presents an osmotic hydration sensor which can record the level of hydration as a function of osmotic pressure in a sodium-chloride solution that simulates the interstitial fluid in the body. The osmotic pressure is recorded by the aid of an ion-exchange membrane that facilitates the migration of water and cations, in favor of RO or gas separation membranes. The hydration sensor is designed to be coupled to an inductively powered read out integrator circuit that has previously been shown to consume up to 76µW of power. The dynamic range spans a state of serious overhydration (220 mOsm L-1) to a serious state of dehydration (340 mOsm L-1) with a response time of approximately 7 hours (for ∆hydration = 20%).

• Häfliger, Philipp (2011). Interview with Philipp Hafliger. Electronics Letters.  ISSN 0013-5194.  47(26), s S17- S17 . doi: 10.1049/el.2011.2686
• Häfliger, Philipp & Constandinou, T (2010). Guest Editorial-Special Issue on Selected Papers From ISCAS 2009. IEEE Transactions on Biomedical Circuits and Systems.  ISSN 1932-4545.  4(3), s 137- 138 . doi: 10.1109/TBCAS.2010.2050363
• Azadmehr, Mehdi & Häfliger, Philipp (2005). A Foveated AER Imager Chip.
• Serrano-Gotarredona, R; Oster, Matthias; Häfliger, Philipp & Riis, Håvard Kolle (2005). AER Building Blocks for Multi-Layer Multi-Chip Neuromorphic Vision Systems.
• Abrahamsen, Jens Petter; Häfliger, Philipp & Lande, Tor Sverre (2004). A Time Domain Winner-Take-All network of Integrate-and-Fire Neurons.
• Riis, Håvard Kolle & Häfliger, Philipp (2004). Spike Based Learning with Weak Multi-Level Static Memory. Vis sammendrag

  In this paper we present a VLSI implementation of a learning synapse that uses a spike based learning rule to adjust its weight. The weight is stored on a recently presented weak multi-level static memory cell (MLSM). This memory cell stores a voltage on a capacitance and that voltage is weakly driven to the closest of several stable levels. We verified the suitability of this memory for this task in a VLSI chip implementation. An array of integrate and fire neurons with four of these learning synapses each was implemented on a 0.6 micron AMS CMOS chip. The learning capability of these neurons was tested in a simple pattern recognition task in a two neuron network. The neurons learned to recognize spatio-temporal patterns of coincident spikes to different synapses. Crossinhibition between them lead to improved decorrelation of the output spikes, inducing a tendency in the neurons to specialize on different patterns.

• Häfliger, Philipp & Riis, Håvard Kolle (2003). A Multi-Level Static Memory Cell. Vis sammendrag

  This paper introduces a static multi-level memory cell that was conceived to store state variables in neuromorphic on-chip learning applications. It consists of a capacitance that holds a voltage and an array of `fusing' amplifiers that are connected as followers. These followers drive their output towards the voltage level of the input like normal followers, but only if the difference between input and output is smaller than about 120mV. The inputs to this 'fusing' follower array determine the stable voltage levels of the memory cell. All follower-outputs are connect to the storage capacitance and thus the voltage is always driven to the closest stable level. The cell content can be changed by injecting current into the capacitance. This form of storage offers arguably a better compromise between desirable and undesirable properties for neuromorphic learning systems than alternative solutions (e.g. non-volatile analog storage on floating gates or digital static storage in combination with AD/DA conversion), as shall be discussed in the following.

• Häfliger, Philipp & Bergh, Frode (2002). An integrated circuit computing shift in stereo pictures using time domain spike signals. Vis sammendrag

  A VLSI implementation of an electronic circuit is presented that estimates the shift between two overlapping one-dimensional pictures. This information can for instance be used to compute distance in stereo vision. The main novelty of this particular circuit is that it performs part of the computation on time domain encoded signals. It translates the analog pixel values into narrow width pulse signals, referred to as spikes in the following. The relative timing of those spikes represents the pixel values: earlier spikes indicate a higher pixel intensity. Thus matching intensities are identified by detecting coincident spikes by simple AND gates. In a two-dimensional array of coincidence detectors the circuit computes the best matching shift of the two input arrays. A prototype of the circuit has been implemented and tested on a 0.6$\mu$m AMS chip. The chip communicates its analog input and output values by address event representation.

• Häfliger, Philipp (2001). Asynchronous event redirecting in bio-inspired communication. Vis sammendrag

  The paper presents the FPGA implementation of a programmable asynchronous digital circuit (henceforth called AE-map) that remaps `address events'. Address event representation (AER) is an event driven communication protocol originally used in VLSI implementations of neural networks to transfer action potentials (neural voltage pulses) between neurons. More generally speaking it is suited to transmit a number of analog values that are coded in frequency of events over an asynchronous digital bus. The AE-map allows to redirect such events between an AE sender and an AE receiver, thereby for instance programming the connection scheme of a neural network. Earlier approaches for redirecting AEs have used digital synchronous devices such as DSPs or microcontrollers. The more simple and more dedicated asynchronous solution presented here is more energy efficient, does not impose a discretization on the time axis and achieves a much faster throughput. In the present implementation AEs (9 bit input, 7 bit output) can be processed at intervals of less than 84ns per output AE.

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