Quantitative Measurement of Thermal Conductivity by SThM Technique: Measurements, Calibration Protocols and Uncertainty Evaluation.

Thermal management is a key issue for the downsizing of electronic components in order to optimise their performance. These devices incorporate more and more nanostructured materials, such as thin films or nanowires, requiring measurement techniques suitable to characterise thermal properties at the nanoscale, such as Scanning Thermal Microscopy (SThM). In active mode, a hot thermoresistive probe scans the sample surface, and its electrical resistance R changes as a function of heat transfers between the probe and sample. This paper presents the measurement and calibration protocols developed to perform quantitative and traceable measurements of thermal conductivity k using the SThM technique, provided that the heat transfer conditions between calibration and measurement are identical, i.e., diffusive thermal regime for this study. Calibration samples with a known k measured at the macroscale are used to establish the calibration curve linking the variation of R to k. A complete assessment of uncertainty (influencing factors and computational techniques) is detailed for both the calibration parameters and the estimated k value. Outcome analysis shows that quantitative measurements of thermal conductivity with SThM (with an uncertainty value of 10%) are limited to materials with low thermal conductivity (k<10Wm-1K-1).

Connecting During COVID-19: A Protocol of a Volunteer-Based Telehealth Program for Supporting Older Adults' Health.

Introduction: Social-distancing due to COVID-19 has led to social isolation, stress, and mental health issues in older adults, while overwhelming healthcare systems worldwide. Telehealth involving phone calls by trained volunteers is understudied and may be a low-cost, scalable, and valuable preventive tool for mental health. In this context, from patient participatory volunteer initiatives, we have adapted and developed an innovative volunteer-based telehealth intervention program for older adults (TIP-OA). Methods and analysis: To evaluate TIP-OA, we are conducting a mixed-methods longitudinal observational study. Participants: TIP-OA clients are older adults (age ≥ 60) recruited in Montreal, Quebec. Intervention: TIP-OA volunteers make weekly friendly phone calls to seniors to check in, form connections, provide information about COVID-19, and connect clients to community resources as needed. Measurements: Perceived stress, fear surrounding COVID-19, depression, and anxiety will be assessed at baseline, and at 4- and 8-weeks. Semi-structured interviews and focus groups will be conducted to assess the experiences of clients, volunteers, and stakeholders. Results: As of October 15th, 2020, 150 volunteers have been trained to provide TIP-OA to 305 older clients. We will consecutively select 200 clients receiving TIP-OA for quantitative data collection, plus 16 volunteers and 8 clinicians for focus groups, and 15 volunteers, 10 stakeholders, and 25 clients for semi-structured interviews. Discussion: During COVID-19, healthcare professionals' decreased availability and increased needs related to geriatric mental health are expected. If successful and scalable, volunteer-based TIP-OA may help prevent and improve mental health concerns, improve community participation, and decrease healthcare utilization. Clinical Trial Registration: ClinicalTrials.gov NCT04523610; https://clinicaltrials.gov/ct2/show/NCT04523610?term=NCT04523610&draw=2&rank=1.

A dark mode in scanning thermal microscopy.

The need for high lateral spatial resolution in thermal science using Scanning Thermal Microscopy (SThM) has pushed researchers to look for more and more tiny probes. SThM probes have consequently become more and more sensitive to the size effects that occur within the probe, the sample, and their interaction. Reducing the tip furthermore induces very small heat flux exchanged between the probe and the sample. The measurement of this flux, which is exploited to characterize the sample thermal properties, requires then an accurate thermal management of the probe-sample system and to reduce any phenomenon parasitic to this system. Classical experimental methodologies must then be constantly questioned to hope for relevant and interpretable results. In this paper, we demonstrate and estimate the influence of the laser of the optical force detection system used in the common SThM setup that is based on atomic-force microscopy equipment on SThM measurements. We highlight the bias induced by the overheating due to the laser illumination on the measurements performed by thermoresistive probes (palladium probe from Kelvin Nanotechnology). To face this issue, we propose a new experimental procedure based on a metrological approach of the measurement: a SThM "dark mode." The comparison with the classical procedure using the laser shows that errors between 14% and 37% can be reached on the experimental data exploited to determine the heat flux transferred from the hot probe to the sample.