Flexible, scalable, and efficient thermoelectric touch detector based on PDMS and Graphite flakes

This paper presents freestanding thermoelectric touch detectors consisting of graphite conductive flakes into a polydimethylsiloxane matrix. An optimal concentration of graphite flakes (45 wt%) lead to robust and homogeneous detectors that exhibited signal-noise ratio values up to 170 with rise and falling times below 1 s and 7 s, respectively. The detectors performance was stable over continuous operation and did not reveal significant degradation while bended under different curvature radii (45, 25 and 15 mm) and consecutive bending cycles. Moreover, the twist of the thermal gradient direction between the electrodes of the detector enables a Yes or No response which opens new usage possibilities. Therefore, this work provides an efficient way to develop robust, low-cost, and scalable thermal detectors with potential use in wearable technologies.

Availability and safety assessment of infrared neural stimulation at high repetition rate through an implantable optrode

An implantable optrode with micro-thermal detectors was designed to investigate the availability and safety of INS using high repetition rates. Optical auditory brainstem responses (oABRs) were recorded in normal-hearing guinea pigs, and the energy thresholds, pulse durations, and amplitudes evoked by the varied stimulus repetitions were analyzed. Stable oABRs could be evoked through INS even as the repetition rate of stimulation reached 19[Formula: see text]kHz. The energy threshold of oABRs was elevated, the amplitudes decreased as pulse durations increased and repetition rates were higher, and the latencies were delayed as the pulse durations increased. The temperature variation curves on the site of stimulation significantly increased as the pulse duration increased to 400 [Formula: see text]s. INS elevated the temperature around the stimulus site area via thermal accumulation during radiation, especially when higher repetition stimuli were used. Our results demonstrate that high repetition infrared stimulations can safely evoke stable and available oABRs in normal-hearing guinea pigs.

Thermal Sensors for Contactless Temperature Measurements, Occupancy Detection, and Automatic Operation of Appliances during the COVID-19 Pandemic: A Review

The worldwide spread of COVID-19 has forced us to adapt to a new way of life made of social distancing, avoidance of physical contact and temperature checks before entering public places, in order to successfully limit the virus circulation. The role of technology has been fundamental in order to support the required changes to our lives: thermal sensors, in particular, are especially suited to address the needs arisen during the pandemic. They are, in fact, very versatile devices which allow performing contactless human body temperature measurements, presence detection and people counting, and automation of appliances and systems, thus avoiding the need to touch them. This paper reviews the theory behind thermal detectors, considering the different types of sensors proposed during the last ten years, while focusing on their possible employment for COVID-19 related applications.

Trends in Performance Limits of the HOT Infrared Photodetectors

The cryogenic cooling of infrared (IR) photon detectors optimized for the mid- (MWIR, 3–5 µm) and long wavelength (LWIR, 8–14 µm) range is required to reach high performance. This is a major obstacle for more extensive use of IR technology. Focal plane arrays (FPAs) based on thermal detectors are presently used in staring thermal imagers operating at room temperature. However, their performance is modest; thermal detectors exhibit slow response, and the multispectral detection is difficult to reach. Initial efforts to develop high operating temperature (HOT) photodetectors were focused on HgCdTe photoconductors and photoelectromagnetic detectors. The technological efforts have been lately directed on advanced heterojunction photovoltaic HgCdTe detectors. This paper presents the several approaches to increase the photon-detectors room-temperature performance. Various kinds of materials are considered: HgCdTe, type-II AIIIBV superlattices, two-dimensional materials and colloidal quantum dots.

Матричные фотоприемные устройства ИК‑диапазона: «постпандемические» тенденции развития. Часть II

В первой части обзора ( см. Фотоника. 2020; 14(3): 234–244) были рассмотрены инфракрасные детекторы тепловизионной техники. Устройства востребованы в системах и комплексах гражданской и медицинской термографии, охранного и пожарного наблюдения, персональных системах ночного видения и обеспечения безопасности. Во второй части обзора рассмотрены охлаждаемые МФПУ для спектрального диапазона 3–5 мкм, 8–12 мкм, неохлаждаемые МФПУ. Представлено сравнение тепловых детекторов разного типа от разных мировых производителей. Дан экспертный прогноз изменений динамики роста рынка и его пост-пандемические тенденции развития. The first part of the review (see Photonics Russia.2020; 14(3): 234–244) deals with infrared detectors of thermal imaging technology. The devices are in demand in systems and complexes of civil and medical thermography, security and fire surveillance, personal night vision and security systems. The second part of the review deals with cooled APDs for the spectral range of 3–5 microns, 8–12 microns, uncooled APDs. A comparison of thermal detectors of various types by different world manufacturers is presented. An expert forecast of changes in market growth dynamics and trends of its post-pandemic development is given.