DMD-based software-configurable spatially-offset Raman spectroscopy for spectral depth-profiling of optically turbid samples

Spectral depth-profiling of optically turbid samples is of high interest to a broad range of applications. We present a method for measuring spatially-offset Raman spectroscopy (SORS) over a range of length scales by incorporating a digital micro-mirror device (DMD) into a sample-conjugate plane in the detection optical path. The DMD can be arbitrarily programmed to collect/reject light at spatial positions in the 2D sample-conjugate plane, allowing spatially offset Raman measurements. We demonstrate several detection geometries, including annular and simultaneous multi-offset modalities, for both macro- and micro-SORS measurements, all on the same instrument. Compared to other SORS modalities, DMD-based SORS provides more flexibility with only minimal additional experimental complexity for subsurface Raman collection

Feasibility of integrated high‐wavenumber Raman imaging and fingerprint Raman spectroscopy for fast margin assessment in breast cancer surgery

Intraoperative assessment of surgical margins remains one of the main challenges in cancer surgery. Raman spectroscopy can detect cancer cells with high accuracy, but it is time‐consuming. In this paper, we investigated a selective‐sampling Raman spectroscopy approach, based on high wavenumber (HW) Raman imaging (spectral range 2,500–3,500 cm−1) and fingerprint Raman spectroscopy (spectral range 600–1,800 cm−1), to reduce the overall tissue analysis time while maintaining high diagnostic accuracy. HW Raman mapping was used as a first step to identify the adipose tissue regions based on the C–H stretching bands at 2,700–2,950 cm−1. As residual tumors are typically found in nonadipose tissue, an algorithm was developed to allocate sampling points for fingerprint Raman spectroscopy at locations corresponding to low intensity in the HW‐Raman maps. Preliminary results show that HW‐Raman imaging based on a 671 nm laser is effective and fast for mapping of adipose tissue in breast resections, with typical imaging times of 2 min for tissue areas as large as 2 × 2 cm2 areas. Albeit the remaining high fluorescence background in the fingerprint region prevents the use of single 671‐nm laser, the HW Raman imaging can be still exploited in combination with 785‐nm excitation Raman spectroscopy for identifying residual tumor. Although this study demonstrates the feasibility of this approach, further improvements, such as using single element detectors for HW Raman imaging, are required to increase the analysis speed further towards intraoperative use in the routine clinical setting

Applications of spatial light modulators in Raman spectroscopy

Advances in consumer display screen technologies have historically been adapted by researchers across the fields of optics as they can be used as electronically controlled spatial light modulators (SLMs) for a variety of uses. The performance characteristics of such SLM devices based on liquid crystal (LC) and digital-micro-mirror device (DMD) technologies in particular has developed to the point where they are compatible with increasingly sensitive instrumental applications, for example Raman spectroscopy. SLMs provide additional flexibility, from modulation of the laser excitation (including multiple laser foci patterns), manipulation of microscopic samples (optical trapping) or selection of sampling volume (adaptive optics or spatially offset Raman spectroscopy), to modulation in the spectral domain for high-resolution spectral filtering or multiplexed/compressive fast detection. Here, we introduce the benefits of different SLM devices as a part of Raman instrumentation, and provide a variety of recent example applications which have benefited from their incorporation into a Raman system

A novel resilience assessment for active distribution networks including a DER voltage regulation scheme considering windstorms

Increasing incidences of extreme weather events pose significant challenges to the electrical grids in terms of the ability to withstand those high-impact eventualities. This paper proposes a resilience assessment framework for net-zero active distribution networks (ADNs) to tackle the impacts of extreme windstorms where only renewable energy resources (RESs) and battery energy storage systems (BESSs) are considered. To accurately capture the influence of windstorms on the grid, a detailed spatiotemporal representation of grid system assets and their exposure to the wind has been implemented. The suggested day-ahead resilience assessment is based on a three-stage approach. The first stage computes the probabilities of failure of each line and determines the most vulnerable ones. The second stage obtains the optimal grid configuration based on the outcomes of the first stage given the available non-dispatchable RESs and commits the available resources in each island to minimize the loss of load during the windstorm. If such a value is still larger than zero after the second stage, a novel voltage regulation scheme is applied in the third stage, taking advantage of the RESs and BESSs in each island. The proposed resilience assessment has been evaluated using the IEEE 33-bus test system with the meteorological data retrieved from an actual windstorm event occurred in the UK on the 20th of February. The outcomes of this paper underscore that a significant reduction in load shedding during such extreme events can be achieved, thus having a notable enhancement to the overall resilience of the system. Finally, the performance of this approach is compared with other resilience-oriented methods for windstorms, where the benefits of using the scheme reported in this paper are highlighted and quantified

Feasibility of spatially-offset Raman spectroscopy for in-vitro and in-vivo monitoring mineralisation of bone tissue-engineering scaffolds

We investigated the feasibility of using spatially-offset Raman spectroscopy (SORS) for non-destructive characterisation of bone tissue engineering scaffolds. The deep regions of these scaffolds, or scaffolds implanted subcutaneously in live animals, are typically difficult to measure by confocal Raman spectroscopy techniques because of the limited depth penetration of light caused by the high level of light scattering. Layered samples consisting of bioactive glass foams (IEIC16), 3D-printed biodegradable poly-(lactic-co-glycolic acid) scaffolds (PLGA) and hydroxyapatite powder (HA) were used to mimic non-destructive detection of bio-mineralisation for intact real-size 3D tissue engineering constructs. SORS spectra were measured with a new SORS instrument using a digital micro-mirror device (DMD) to allow software selection of the spatial offsets. The results show that HA can be reliably detected at depths of 0-2.3 mm, which corresponds to the maximum accessible spatial offset of the current instrument. The intensity ratio of Raman bands associated to the scaffolds and HA with the spatial offset depended on the depth at which HA was located. Furthermore, we show the feasibility for in-vivo monitoring mineralisation of scaffold implanted subcutaneously by demonstrating the ability to measure transcutaneously Raman signals of the scaffolds and HA (fresh chicken skin used as a top layer). The ability to measure spectral depth profiles at high speed (5 s acquisition time), and the ease of implementation, make SORS a promising approach for non-invasive characterisation of cell/tissue development in-vitro, and for long-term in-vivo monitoring the mineralisation in 3D scaffolds subcutaneously implanted in small animals