Graphene displays properties that make it appealing for neuroregenerative medicine, yet its interaction with peripheral neurons has been scarcely investigated. Here, we culture on graphene two established models for peripheral neurons: PC12 cells and DRG primary neurons. We perform a nano-resolved analysis of polymeric coatings on graphene and combine optical microscopy and viability assays to assess the material cytocompatibility and influence on differentiation. We find that differentiated PC12 cells display a remarkably increased neurite length on graphene (up to 27%) with respect to controls. Notably, DRG primary neurons survive both on bare and coated graphene. They present dense axonal networks on coated graphene, while they form cell islets characterized by dense axonal bundles on uncoated graphene. These findings indicate that graphene holds potential for nerve tissue regeneration and might pave the road to novel concepts of active nerve conduits.

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Peripheral Neuron Survival and Outgrowth on Graphene

The pinned photodiode is the primary photodetector structure used in most CCD and CMOS image sensors. This paper reviews the development, physics, and technology of the pinned photodiode.

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A Review of the Pinned Photodiode for CCD and CMOS Image Sensors

This paper investigates terahertz detectors fabricated in a low-cost 130 nm silicon CMOS technology. We show that the detectors consisting of a nMOS field effect transistor as rectifying element and an integrated bow-tie coupling antenna achieve a record responsivity above 5 kV/W and a noise equivalent power below 10 pW/Hz(0.5) in the important atmospheric window around 300 GHz and at room temperature. We demonstrate furthermore that the same detectors are efficient for imaging in a very wide frequency range from ~0.27 THz up to 1.05 THz. These results pave the way towards high sensitivity focal plane arrays in silicon for terahertz imaging.

Broadband terahertz imaging with highly sensitive silicon CMOS detectors

Single-photon avalanche diode (SPAD) arrays are solid-state detectors that offer imaging capabilities at the level of individual photons, with unparalleled photon counting and time-resolved performance. This fascinating technology has progressed at a very fast pace in the past 15 years, since its inception in standard CMOS technology in 2003. A host of architectures have been investigated, ranging from simpler implementations, based solely on off-chip data processing, to progressively "smarter" sensors including on-chip, or even pixel level, time-stamping and processing capabilities. As the technology has matured, a range of biophotonics applications have been explored, including (endoscopic) FLIM, (multibeam multiphoton) FLIM-FRET, SPIM-FCS, super-resolution microscopy, time-resolved Raman spectroscopy, NIROT and PET. We will review some representative sensors and their corresponding applications, including the most relevant challenges faced by chip designers and end-users. Finally, we will provide an outlook on the future of this fascinating technology.

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Single-photon avalanche diode imagers in biophotonics: review and outlook

We introduce a 512 × 424 time-of-flight (TOF) depth image sensor designed in a TSMC 0.13 μm LP 1P5M CMOS process, suitable for use in Microsoft Kinect for XBOX ONE. The 10 μm × 10 μm pixel incorporates a TOF detector that operates using the quantum efficiency modulation (QEM) technique at high modulation frequencies of up to 130 MHz, achieves a modulation contrast of 67% at 50 MHz and a responsivity of 0.14 A/W at 860 nm. The TOF sensor includes a 2 GS/s 10 bit signal path, which is used for the high ADC bandwidth requirements of the system that requires many ADC conversions per frame. The chip also comprises a clock generation circuit featuring a programmable phase and frequency clock generator with 312.5-ps phase step resolution derived from a 1.6 GHz oscillator. An integrated shutter engine and a programmable digital micro-sequencer allows an extremely flexible multi-gain/multi-shutter and multi-frequency/multi-phase operation. All chip data is transferred using two 4-lane MIPI D-PHY interfaces with a total of 8 Gb/s input/output bandwidth. The reported experimental results demonstrate a wide depth range of operation (0.8–4.2 m), small accuracy error ( $ 1%), very low depth uncertainty ( $ 0.5% of actual distance), and very high dynamic range ( $>$ 64 dB).

A 0.13 μm CMOS System-on-Chip for a 512 × 424 Time-of-Flight Image Sensor With Multi-Frequency Photo-Demodulation up to 130 MHz and 2 GS/s ADC

Semiconductor sensors for neutron detection have been initially proposed as direct replacement of 3He detectors but have recently raised interest in imaging systems. We have developed a monolithic sensor with high spatial granularity in SOIPIX technology for the detection of alpha particles of energy compatible with the reaction products of neutrons with typical converter materials. The chipset is composed by the main pixel matrix and the test structures needed for a better understanding of the chip functionality and for studying the electronic tuning strategies. The fabricated prototypes have been recently delivered and the first tests under alpha source have been performed. In this paper we will present the proposed devices and the results of the experimental characterization.

Development and characterization of a novel alpha particle SOI pixel sensor for neutron detection

In this paper a preliminary characterization of an 8 × 6 pixels, FET-based THz imager with on-chip antennas is presented. The sensor was designed and fabricated in a standard 150 nm CMOS technology and it takes advantage of a Switched Capacitor Band-Pass Filter (SC-BPF) followed by a sampling and amplifying stage for the readout chain, implemented at the pixel level.

A 8 × 6 pixel THz focal plane array with per-pixel high-gain readout channel in 150 nm CMOS technology

The present paper describes a time-based technique for resistive detector. Thanks to the comparison with a reference resistance, the circuit easily compensate the baseline contribution, thus extending the dynamic range of the measurement. The implemented circuit is based on a resistance to time converter followed by a time comparator for signal comparison. Differently from existing time-based technique, the proposed approach allows increasing the sensitivity of the detection by increasing the time of the measurement. The circuit exhibits a measured resolution in the order of 20ppm with a nominal value of resistance of about 3MΩ while the maximum dynamic range is of about 40dB.

A time-based technique for a resistive detector

A compact quantum random number generator based on an array of Single Photon Avalanche Diode (SP AD) is presented here. As the main feature, the proposed chip has the capability to generate random numbers without the use of an external source of light. In the present approach, SP AD devices are used as emitters and as detectors. An embedded logic allows distinguishing dark events from events coming from the photon emission. The extracted random bit sequence shows a quite uniform distribution and after being post-processed by means of an integrated circuit, used to maximize the entropy of the system, is able to pass the AIS31 test. The average bit rate is 400 kbps.

A monolithic SPAD-based random number generator for cryptographic application

We present the results of Montecarlo simulations and measurements focusing on the analysis of two techniques aimed at reducing the negative effect of background light in Single Photon Avalanche Diode (SPAD)-based Light Detection And Ranging (LiDAR) systems. The first technique, known as photon coincidence technique, exploits the temporal proximity of multiple detections to reject background light and maximize the detection of photons belonging to the target reflection. The second technique, named Auto-Sensitivity (AS) technique, reduces the photon-detection probability (PDP) if a certain background illumination level is detected, to avoid the risk of saturating SPADs due to intense background level. The two methods are first compared to each other, showing that the photon coincidence technique outperforms the AS technique. Then, the two techniques are operated together, resulting in an increase of the maximum achievable measurement range if the AS technique is applied on top of the photon coincidence technique.

Matteo Perenzoni

Papers

Development and characterization of a novel alpha particle SOI pixel sensor for neutron detection

A 8 × 6 pixel THz focal plane array with per-pixel high-gain readout channel in 150 nm CMOS technology

A time-based technique for a resistive detector

A monolithic SPAD-based random number generator for cryptographic application

Comparison of background-rejection techniques for SPAD-based LiDAR systems