## 4 Conclusions  
This paper proposes a GGP-GMR system with a linear CCD as a miniaturized solution for liquid assay detection based on fluorescence-based and colorimetric measurements. A comparison of the proposed system with a commercial portable spectrometer indicated that the location and intensity of the MICP obtained using the proposed system effectively correlated with the peak wavelength and its corresponding intensity obtained with the spectrometer. The results of the serial dilution tests in practical assays based on fluorescence-based and two colorimetric measurements revealed that the GGP-GMR/CCD system achieved comparable sensitivity and LOD results to those obtained of the commercial spectrometer. For the practical fluorescent assays for AB580 and the colorimetric assay for albumin quantification, the LODs obtained with the two detection systems were very close to the value recommended by the manufacturer. By contrast, the LODs observed in the colorimetric assay for creatinine detection for the GGP-GMR/CCD system and spectrometer were worse than that suggested by the manufacturer. The main reason for this result is the relatively proficiency in performing the experiments and the marginal environmental lighting fluctuation. A better shield or package for the developed system is expected to reduce the recorded intensity fluctuation under environmental lighting to reduce the experimental noise and thus further improve the LOD. Nevertheless, the results obtained with the GGP-GMR/CCD system agreed well with those obtained using a commercial spectrometer for all three practical assays. In summary, a GGP-GMR filter with a length of less than 2.5 mm can achieve a spectral detection range of 500-700 nm, which can be further extended to cover additional assays. Through a direct measurement of the location and intensity of the MICP on the CCD, the peak wavelength and its intensity obtained from the fluorescent or colorimetric assays can be determined without using a bulky spectrometer. The compact size of the GGP-GMR device and its simple optical path design configuration with a CCD enable accurate assay detection based on fluorescence emission and absorption measurement; thus, the proposed  
Figure 8: Transmission measured with the (**a**) GGP-GMR/CCD and (**b**) spectrometer. Dose response curves of the (**c**) MICP intensity and (**d**) peak wavelength intensity as functions of the albumin concentration. (**e**) Correlation between the two measurement systems. device has the potential to be integrated with microfluidic chips, portable devices, or smartphones for various point-of-care applications. The following are available online at [[https://www.mdpi.com/article/10_3390/s21082797/s1](https://www.mdpi.com/article/10_3390/s21082797/s1)]([https://www.mdpi.com/article/10_3390/s21082797/s1](https://www.mdpi.com/article/10_3390/s21082797/s1)), Figure S1: The relationship between the MICP and the incident wavelength, Figure S2: (a) GGP-GMR on top of a CCD. (b) Customized sample chamber with sample inside. (c) Customized sample chamber with lid, Figure S3: Fluorescence emission from different concentrations of FAM measured using (a) a spectrometer and (b) the proposed GGP-GMR/CCD system, Figure S4: Dose response curve obtained using the (a) GGP-GMR/CCD system and (b) spectrometer. (c) This figure displays the correlation between the normalized intensity of the peak wavelength and that of the MICP, Figure S5: (a) Peak wavelength (blue) and measured MICP (orange) as a function of the concentration. (b) Correlation between the peak wavelength and the MICP, Table S1: Composition of artificial urine. Conceptualization, C.-S.H. ; methodology, C.-S.H., J.-J.G., [PERSON]-H.W. and C.-W.C.; software, J.-J.G. ; validation, [PERSON]-J.G. and C.-W.C.; formal analysis, C.-S.H., [PERSON]-J.G. and C.-W.C.; investigation, C.-S.H., [PERSON]-J.G. and C.-W.C.; resources, C.-S.H., J.-J.G., [PERSON]-[PERSON] and C.-W.C.; data curation, J.-J.G. and C.-W.C.; writing--original draft preparation, C.-S.H.