Machine Learning Enabled Image Analysis of Time‐Temperature Sensing Colloidal Arrays

Abstract

Smart, responsive materials are required in various advanced applications ranging from anti-counterfeiting to autonomous sensing. Colloidal crystals are a versatile material class for optically based sensing applications owing to their photonic stopband. A careful combination of materials synthesis and colloidal mesostructure rendered such systems helpful in responding to stimuli such as gases, humidity, or temperature. Here, an approach is demonstrated to simultaneously and independently measure the time and temperature solely based on the inherent material properties of complex colloidal crystal mixtures. An array of colloidal crystals, each featuring unique film formation kinetics, is fabricated. Combined with machine learning-enabled image analysis, the colloidal crystal arrays can autonomously record isothermal heating events -readout proceeds by acquiring photographs of the applied sensor using a standard smartphone camera. The concept shows how the progressing use of machine learning in materials science has the potential to allow non-classical forms of data acquisition and evaluation. This can provide novel insights into multiparameter systems and simplify applications of novel materials.

Shape memory photonic materials: fabrication and emerging applications

“…9b). 143 Similarly, Zhang et al designed SMPM-based chromogenic sensors that can monitor the ethanol concentration in the residual solution and distillate during the distillation process of the ethanol–water mixture in real time (Fig. 9c).…”

A bio-inspired colorimetric sensor based on ethylene glycol – non-close-packed photonic crystals for visual monitoring of ammonia

“…Colorimetric sensors based on photonic crystals (PCs) have gained interest in the visual sensing of physical, [17][18][19][20][21][22] chemical [23][24][25] and biological stimuli. [26][27][28] Photonic crystals are periodic dielectric materials, 29,30 and their photonic band gap (PBG) satisfies Bragg's diffraction law:…”

“…Colorimetric sensors based on photonic crystals (PCs) have gained interest in the visual sensing of physical, 17–22 chemical 23–25 and biological stimuli. 26–28 Photonic crystals are periodic dielectric materials, 29,30 and their photonic band gap (PBG) satisfies Bragg's diffraction law: n eff 2 = n A 2 f A + n B 2 (1 − f A )where m is the diffraction order, λ is the photonic band gap, d is the lattice distance, θ is the angle of incidence, n eff is the effective refractive index, n A and n B are the refractive index of medium A and B, respectively, and f A is the total volume percentage of medium A.…”

Hydrogen Bond‐Mediated Self‐Shielded Moisture‐Responsive Structural Color for Time‐Temperature Indicating

“…[ 21 ] For pursuing smart TTIs, diverse time‐dependent thermal‐responsive PCs have been designed. [ 22 ] These materials demonstrated swift and irreversible color changes upon reaching temperatures beyond their glass transition temperature or lower critical solution temperature. However, the critical temperature for continuous color changes in PCs exceeded 0 °C and even higher than room temperature, making them unsuitable for monitoring time‐temperature dynamics in low‐temperature environments.…”