A Portable Ultrawideband Confocal Raman Spectroscopy System with a Handheld Probe for Skin Studies

Abstract

Confocal Raman spectroscopy (CRS) has shown potential in non-invasive skin analysis. However, current CRS systems have various limitations including a narrow detection band, large size, non-flexibility, slowness, and complexity, which hinder their clinical applications. Herein, we developed a portable ultrawideband CRS system with a fiber-based handheld probe to acquire the Raman spectra in both fingerprint and high wavenumber regions in a fast and quasi-simultaneous way. Dual-wavelength excitation with a dualpassband laser cleaning filter and high-speed fiber array multiplexer was adopted instead of a specialized grating and detector to achieve instant switching between the detection regions and improve system robustness. Preliminary in vivo results demonstrated its depth profiling capability in an ultrawide detection range for stratum corneum thickness, natural moisturizing factor, and water content quantification, indicating its great potential in a wide range of clinical and cosmeceutical applications.

An all metasurface-based fiber needle probe for Raman spectroscopy

“…In this paper, we have proposed an all-metasurface-enabled fiber needle probe for dual-wavelength excitation Raman spectroscopy devices. The new design reduces the overall size by 100 times and improves the optical performance of the existing handheld probe [13]. It consists of five metasurfaces that replace five conventional optical components in the original design.…”

“…The five metasurfaces in our design include 1) 671 nm narrow band pass filter (NBPF), 2) 671 nm off-axis focusing metalens, 3) 785 nm narrow band pass filter, 4) 785 nm off-axis focusing metalens, and 5) 810-910 nm broadband achromatic on-axis focusing metalens. Metasurface 1)-4) were designed to replace all the optical components in the excitation beam path in the earlier design [13], i.e., metasurface 1) and 3) for the dual-passband laser cleaning filters and metasurface 2) and 4) for the fiber array multiplexing module, the collimator, and the objective. Metasurface 5) was designed to replace the optical components in the collection beam path including the objective, the notch filter, and the collimator.…”

“…Recently there has been a lot of development in miniaturizing Raman spectroscopy-based devices for in vivo studies [10][11][12]. We have earlier reported a handheld portable Raman spectroscopy device for skin analysis [13].…”

Open-sourced Raman spectroscopy data processing package implementing a baseline removal algorithm validated from multiple datasets acquired in human tissue and biofluids

“…Spatial scales consist of confocal microscopy applications for imaging at cellular resolution, 6 – 8 up to mesoscopic scales for biofluids, 9 – 13 in situ tissue measurements during surgery, 14 – 16 and more recently, at macroscopic scales. 17 – 19 For these applications, tissue and fluids were submitted to different pre-processing methodologies. These include in situ in vivo (without sample pre-processing), in situ ex vivo (aqueous solution to maintain tissue viability/integrity), deposition on ex vivo microscope slides for formalin-fixed, paraffin-embedded tissue, and centrifugation for blood and saliva applications.…”

Simultaneous Dual-Wavelength Source Raman Spectroscopy with a Handheld Confocal Probe for Analysis of the Chemical Composition of In Vivo Human Skin

“…Therefore, a confocal Raman spectroscopy with a 532 nm excitation laser requires a very high power laser source (>100 mW) to increase the signal-to-noise ratio, which is not suitable for in vivo subject testing. Previously, we developed a CRS system with a flexible handheld probe and quasi-simultaneous dual-wavelength source solution to mitigate this problem by incorporating a fast fiber switch and dual-pass band filter . However, the consecutive acquisitions by two wavelengths at each depth still required separate exposures, which is time consuming.…”