Eashika Ghosh, Aleksandr I. Egunov, D. Karnaushenko, M. Medina‐Sánchez, Oliver G. Schmidt
Abstract The advancement of micro and nanotechnology has led to the manufacturing of miniaturized sensors with improved functionalities for highly sensitive point of care devices. This work is particularly focused on analysing cancer cells and the effect of a model drug on their survival rate. To that end, we developed a highly sensitive rolled-up micro-electrochemical impedance spectroscopy sensor, encapsulated into a microfluidic channel. The sensor was built by strain engineering of shapeable materials and with diameters close to the cell size to improve their sensitivity. To demonstrate the platform performance, we first carried out measurements with different electrode geometries using cell medium at different concentrations. We also performed measurements using cancer cell suspensions, obtaining distinct signals from single cells, cell clusters and cellular debris. Finally, cancer cells were treated with an anticancer drug (Camptothecin), at different concentrations, over the same period, and further analysed using the developed platform.
{"title":"Self-assembled sensor-in-a-tube as a versatile tool for label-free EIS viability investigation of cervical cancer cells","authors":"Eashika Ghosh, Aleksandr I. Egunov, D. Karnaushenko, M. Medina‐Sánchez, Oliver G. Schmidt","doi":"10.1515/freq-2022-0090","DOIUrl":"https://doi.org/10.1515/freq-2022-0090","url":null,"abstract":"Abstract The advancement of micro and nanotechnology has led to the manufacturing of miniaturized sensors with improved functionalities for highly sensitive point of care devices. This work is particularly focused on analysing cancer cells and the effect of a model drug on their survival rate. To that end, we developed a highly sensitive rolled-up micro-electrochemical impedance spectroscopy sensor, encapsulated into a microfluidic channel. The sensor was built by strain engineering of shapeable materials and with diameters close to the cell size to improve their sensitivity. To demonstrate the platform performance, we first carried out measurements with different electrode geometries using cell medium at different concentrations. We also performed measurements using cancer cell suspensions, obtaining distinct signals from single cells, cell clusters and cellular debris. Finally, cancer cells were treated with an anticancer drug (Camptothecin), at different concentrations, over the same period, and further analysed using the developed platform.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"76 1","pages":"729 - 740"},"PeriodicalIF":1.1,"publicationDate":"2022-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47647876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Paul V Gwozdz, Jann Harberts, R. Zierold, R. Blick
Abstract We demonstrate operation of a micropore based flow cytometer in the radio-frequency range. Apart from simply counting micron sized particles, such as cells, with close to nano-second resolution this counter offers the additional benefit of delivering insight into the intracellular environment. Such non-invasive screening of the cell’s interior based on analysing amplitude and phase of the signal is helpful in characterizing the biological activity of cells. In detail we are using heterodyne mixing to demodulate the temporal impedance changes, which are induced by cells translocating through a micropore embedded in a radio-frequency circuit. This allows us to measure every amplitude and phase modulation induced by a translocation event. Herein, we compare the Jurkat cells (human T lymphocytes) recordings with a control group of polystyrene beads. As the cells are measured on a single cell level, the variations on the measured amplitude and phase signals are used, herein, to sense morphological cell changes in real time.
{"title":"Label-free single-cell counting and characterization in the GHz-range","authors":"Paul V Gwozdz, Jann Harberts, R. Zierold, R. Blick","doi":"10.1515/freq-2022-0132","DOIUrl":"https://doi.org/10.1515/freq-2022-0132","url":null,"abstract":"Abstract We demonstrate operation of a micropore based flow cytometer in the radio-frequency range. Apart from simply counting micron sized particles, such as cells, with close to nano-second resolution this counter offers the additional benefit of delivering insight into the intracellular environment. Such non-invasive screening of the cell’s interior based on analysing amplitude and phase of the signal is helpful in characterizing the biological activity of cells. In detail we are using heterodyne mixing to demodulate the temporal impedance changes, which are induced by cells translocating through a micropore embedded in a radio-frequency circuit. This allows us to measure every amplitude and phase modulation induced by a translocation event. Herein, we compare the Jurkat cells (human T lymphocytes) recordings with a control group of polystyrene beads. As the cells are measured on a single cell level, the variations on the measured amplitude and phase signals are used, herein, to sense morphological cell changes in real time.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"76 1","pages":"719 - 728"},"PeriodicalIF":1.1,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41512198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Heine, E. C. Durmaz, Defu Wang, Zhibo Cao, M. Wietstruck, B. Tillack, D. Kissinger
Abstract Dielectric spectroscopy in the sub-THz regime is a promising candidate for microfluidic-based analysis of biological cells and bio-molecules, since multiple vibrational and rotational transition energy levels exist in this frequency range (P. Siegel, “Terahertz technology in biology and medicine,” IEEE Trans. Microw. Theor. Tech., vol. 52, pp. 2438–2447, 2004). This article presents our recent efforts in the implementation of microfluidic channel networks with silicon-based technologies to unleash the potential of an integrated sub-THz microfluidic sensor platform. Various aspects of dielectric sensors, readout systems, flowmeter design as well as implemention- and technology-related questions are addressed. Three dielectric sensor systems are presented operating at 240 GHz realizing transmission-based, reflection-based and full two-port architectures. Furthermore different silicon based microchannel integration techniques are discussed as well as a novel copper pillar-based PCB microchannel method is proposed and successfully demonstrated.
{"title":"Towards a fully integrated sub-THz microfluidic sensor platform for dielectric spectroscopy","authors":"C. Heine, E. C. Durmaz, Defu Wang, Zhibo Cao, M. Wietstruck, B. Tillack, D. Kissinger","doi":"10.1515/freq-2022-0091","DOIUrl":"https://doi.org/10.1515/freq-2022-0091","url":null,"abstract":"Abstract Dielectric spectroscopy in the sub-THz regime is a promising candidate for microfluidic-based analysis of biological cells and bio-molecules, since multiple vibrational and rotational transition energy levels exist in this frequency range (P. Siegel, “Terahertz technology in biology and medicine,” IEEE Trans. Microw. Theor. Tech., vol. 52, pp. 2438–2447, 2004). This article presents our recent efforts in the implementation of microfluidic channel networks with silicon-based technologies to unleash the potential of an integrated sub-THz microfluidic sensor platform. Various aspects of dielectric sensors, readout systems, flowmeter design as well as implemention- and technology-related questions are addressed. Three dielectric sensor systems are presented operating at 240 GHz realizing transmission-based, reflection-based and full two-port architectures. Furthermore different silicon based microchannel integration techniques are discussed as well as a novel copper pillar-based PCB microchannel method is proposed and successfully demonstrated.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"76 1","pages":"685 - 697"},"PeriodicalIF":1.1,"publicationDate":"2022-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49094651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper, a quad-band polarization- and incident-angle independent low-profile metamaterial absorber is proposed. The design consists of three square rings one into another and one plus-shaped slot structure. The size of the unit cell is 11 × 11 mm2 and is printed on an FR-4 substrate having a thickness of 1 mm. It provides 99.2%, 97.6%, 99.3%, and 99.9% absorption at 3.55 GHz, 5.27 GHz, 7.57 GHz, and 11.57 GHz, respectively, thus covering the S, C, and X bands. The surface current distribution of the proposed absorber is also shown at the four resonating frequencies to get a better insight into the design. Moreover, the stability of the proposed design is also validated with different incident angles (for both TE and TM modes) and polarization angles. In addition, a prototype of the proposed absorber structure is also fabricated and then verified experimentally.
{"title":"Analysis of quad-band polarization- and incident-angle independent low profile metamaterial absorber","authors":"Manpreet Kaur, H. Singh","doi":"10.1515/freq-2022-0059","DOIUrl":"https://doi.org/10.1515/freq-2022-0059","url":null,"abstract":"Abstract In this paper, a quad-band polarization- and incident-angle independent low-profile metamaterial absorber is proposed. The design consists of three square rings one into another and one plus-shaped slot structure. The size of the unit cell is 11 × 11 mm2 and is printed on an FR-4 substrate having a thickness of 1 mm. It provides 99.2%, 97.6%, 99.3%, and 99.9% absorption at 3.55 GHz, 5.27 GHz, 7.57 GHz, and 11.57 GHz, respectively, thus covering the S, C, and X bands. The surface current distribution of the proposed absorber is also shown at the four resonating frequencies to get a better insight into the design. Moreover, the stability of the proposed design is also validated with different incident angles (for both TE and TM modes) and polarization angles. In addition, a prototype of the proposed absorber structure is also fabricated and then verified experimentally.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"77 1","pages":"235 - 247"},"PeriodicalIF":1.1,"publicationDate":"2022-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45441295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sarosh Ahmad, Bilal Manzoor, Muhammad Muzamil Shair, Shahid Khan, A. Akram, A. Ghaffar, Ahmed Jamal Abdullah Al-Gburi, E. Ali, F. Arpanaei, Mohammad Alibakhshikenari
Abstract Medical telemetry applications rely heavily on biomedical implanted antennas. These biomedical implanted devices can enhance and monitor patients’ daily life circumstances. A low-profile, downsized size implanted antenna operating at 915 MHz in the industrial, scientific, and medical (ISM) band is suggested in this research. The antenna is a simple slotted patch supplied by a 50-impedance coaxial probe. The radiator is made up of two slotted parasitic patches with one square-shaped outer radiator are manufactured on a Roger Droid RT5880 substrate with a standard height of 0.254 mm (εr = 2.2, tanδ = 0.0009). The entire dimension of the given antenna is 11 × 11 × 0.2514 mm with an electrical size of 0.049λg × 0.049λg × 0.0011λg. The antenna spans a bandwidth of 0.82–1.05 GHz when working inside muscle tissues (25.13 percent). The antenna’s calculations and experimental findings are quite similar. The computed specific absorption rate (SAR) values inside muscle of above 1 g mass tissue are 7.25 W/kg, according to the data. The stated SAR values are lower than the limit set by the Federal Communications Commission (FCC). As a result, the proposed small antenna is a strong contender for biological implantable applications.
{"title":"Novel implantable antenna with miniaturized footprint size for wideband biomedical telemetry applications","authors":"Sarosh Ahmad, Bilal Manzoor, Muhammad Muzamil Shair, Shahid Khan, A. Akram, A. Ghaffar, Ahmed Jamal Abdullah Al-Gburi, E. Ali, F. Arpanaei, Mohammad Alibakhshikenari","doi":"10.1515/freq-2022-0043","DOIUrl":"https://doi.org/10.1515/freq-2022-0043","url":null,"abstract":"Abstract Medical telemetry applications rely heavily on biomedical implanted antennas. These biomedical implanted devices can enhance and monitor patients’ daily life circumstances. A low-profile, downsized size implanted antenna operating at 915 MHz in the industrial, scientific, and medical (ISM) band is suggested in this research. The antenna is a simple slotted patch supplied by a 50-impedance coaxial probe. The radiator is made up of two slotted parasitic patches with one square-shaped outer radiator are manufactured on a Roger Droid RT5880 substrate with a standard height of 0.254 mm (εr = 2.2, tanδ = 0.0009). The entire dimension of the given antenna is 11 × 11 × 0.2514 mm with an electrical size of 0.049λg × 0.049λg × 0.0011λg. The antenna spans a bandwidth of 0.82–1.05 GHz when working inside muscle tissues (25.13 percent). The antenna’s calculations and experimental findings are quite similar. The computed specific absorption rate (SAR) values inside muscle of above 1 g mass tissue are 7.25 W/kg, according to the data. The stated SAR values are lower than the limit set by the Federal Communications Commission (FCC). As a result, the proposed small antenna is a strong contender for biological implantable applications.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"77 1","pages":"293 - 301"},"PeriodicalIF":1.1,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43161374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This paper reports investigations on the effect of array size on the RCS reduction bandwidth of checkerboard metasurfaces (CMS). Three CMSs, one on a Rogers substrate and the remaining on FR4, are considered. While the usual phase deviation criteria are used for the designs on both the substrates, additionally a set of modified criteria recently proposed are used for the FR4 substrate-based designs. While three different sizes – 120 mm2, 240 mm2, and 480 mm2 – are considered for the simulation-based investigations for all the structures, an additional size of 600 mm2 is also considered for one of them. The 8 and 10 dB RCS reduction bandwidths drop as array size increases. The bandwidth reduction is attributable to mutual coupling, as has been reported in an earlier study. As therefore expected, all of the three structures, for all sizes, present the same RCS reduction bandwidth when a mutual coupling mitigation technique is incorporated. For 10 dB RCS reduction bandwidth, this value approaches that estimated by using a mutual coupling independent semi-empirical equation that holds for infinite arrays.
摘要本文研究了阵列大小对棋盘元表面(CMS) RCS约简带宽的影响。考虑了三个cms，一个在Rogers衬底上，其余的在FR4上。虽然通常的相位偏差标准用于两种基板上的设计，但最近提出的一组修改标准用于基于FR4基板的设计。虽然基于模拟的研究考虑了三种不同的尺寸——120 mm2、240 mm2和480 mm2，但其中一种结构还考虑了600 mm2的额外尺寸。8 dB和10 dB RCS减小带宽随着阵列大小的增加而下降。正如之前的一项研究所报道的那样，带宽减少是由于相互耦合造成的。因此，正如预期的那样，当采用相互耦合缓解技术时，对于所有尺寸的所有三种结构都具有相同的RCS减小带宽。对于10db RCS减少带宽，该值接近通过使用相互耦合独立的半经验方程估计的值，该方程适用于无限阵列。
{"title":"On the effect of array size on the radar cross section reduction bandwidth of checkerboard metasurfaces","authors":"Akila Murugesan, K. Selvan","doi":"10.1515/freq-2022-0021","DOIUrl":"https://doi.org/10.1515/freq-2022-0021","url":null,"abstract":"Abstract This paper reports investigations on the effect of array size on the RCS reduction bandwidth of checkerboard metasurfaces (CMS). Three CMSs, one on a Rogers substrate and the remaining on FR4, are considered. While the usual phase deviation criteria are used for the designs on both the substrates, additionally a set of modified criteria recently proposed are used for the FR4 substrate-based designs. While three different sizes – 120 mm2, 240 mm2, and 480 mm2 – are considered for the simulation-based investigations for all the structures, an additional size of 600 mm2 is also considered for one of them. The 8 and 10 dB RCS reduction bandwidths drop as array size increases. The bandwidth reduction is attributable to mutual coupling, as has been reported in an earlier study. As therefore expected, all of the three structures, for all sizes, present the same RCS reduction bandwidth when a mutual coupling mitigation technique is incorporated. For 10 dB RCS reduction bandwidth, this value approaches that estimated by using a mutual coupling independent semi-empirical equation that holds for infinite arrays.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"77 1","pages":"273 - 279"},"PeriodicalIF":1.1,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45492987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this letter, a new microwave sensor of the coaxial resonant cavity with a single-open-ended circuit loaded capacitor is proposed and used to detect the liquids’ complex permittivity. The improved cavity has a higher internal electric field and smaller size when compared with the cylindrical cavity, which gives the sensor a high sensitivity in measuring liquids’ complex permittivity. A coaxial resonant cavity operating in 1.9 GHz was designed in this work. The silicone hose used for the test is inserted vertically from the center of the cavity, and the liquids under test (LUTs) are guaranteed to be 2 ml each time. The dielectric properties of LUTs will cause perturbation to the internal electric field of the cavity. By analyzing the measured data, the sensitivity of the cavity is 0.12%, and the relative errors of the real part of the measured value and the reference value are 3.67%. which shows the measured value has a good agreement with the reference value.
{"title":"Coaxial resonant cavity for measuring complex permittivity of liquids","authors":"Yi Wang, Zhixia Xu, Yulin Feng, Shaojun Fang","doi":"10.1515/freq-2022-0115","DOIUrl":"https://doi.org/10.1515/freq-2022-0115","url":null,"abstract":"Abstract In this letter, a new microwave sensor of the coaxial resonant cavity with a single-open-ended circuit loaded capacitor is proposed and used to detect the liquids’ complex permittivity. The improved cavity has a higher internal electric field and smaller size when compared with the cylindrical cavity, which gives the sensor a high sensitivity in measuring liquids’ complex permittivity. A coaxial resonant cavity operating in 1.9 GHz was designed in this work. The silicone hose used for the test is inserted vertically from the center of the cavity, and the liquids under test (LUTs) are guaranteed to be 2 ml each time. The dielectric properties of LUTs will cause perturbation to the internal electric field of the cavity. By analyzing the measured data, the sensitivity of the cavity is 0.12%, and the relative errors of the real part of the measured value and the reference value are 3.67%. which shows the measured value has a good agreement with the reference value.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"77 1","pages":"229 - 234"},"PeriodicalIF":1.1,"publicationDate":"2022-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47992403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract We demonstrate a full-cycle breath gas sensor system based on terahertz/millimeter-wave gas spectroscopy. The sensor consists of a transmitter and receiver working around 250 GHz based on SiGe BiCMOS technology. Typical detection thresholds are in the ppm range depending on the respective molecule. The data analysis provides partial pressures of the investigated molecules by fitting of spectra which are measured by wavelength modulation. Beside the spectroscopic measurement and the data analysis, a full cycle of breath analysis includes the sampling and the conditioning of the sample tubes. The full cycle takes about 35 min per sample in average. As the system is compact and easy to operate, it allows for on-site analysis of breath samples in medical laboratories or hospitals.
{"title":"A compact breath gas sensor system based on terahertz/millimeter-wave gas spectroscopy","authors":"N. Rothbart, K. Schmalz, R. Koczulla, H. Hübers","doi":"10.1515/freq-2022-0131","DOIUrl":"https://doi.org/10.1515/freq-2022-0131","url":null,"abstract":"Abstract We demonstrate a full-cycle breath gas sensor system based on terahertz/millimeter-wave gas spectroscopy. The sensor consists of a transmitter and receiver working around 250 GHz based on SiGe BiCMOS technology. Typical detection thresholds are in the ppm range depending on the respective molecule. The data analysis provides partial pressures of the investigated molecules by fitting of spectra which are measured by wavelength modulation. Beside the spectroscopic measurement and the data analysis, a full cycle of breath analysis includes the sampling and the conditioning of the sample tubes. The full cycle takes about 35 min per sample in average. As the system is compact and easy to operate, it allows for on-site analysis of breath samples in medical laboratories or hospitals.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"76 1","pages":"669 - 676"},"PeriodicalIF":1.1,"publicationDate":"2022-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46079692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mohamed Atef Hassan, M. Kern, Anh Chu, Gatik Kalra, E. Shabratova, Aleksei Tsarapkin, Neil MacKinnon, K. Lips, C. Teutloff, R. Bittl, J. Korvink, J. Anders
Abstract Electron paramagnetic resonance (EPR) is the gold standard for studying paramagnetic species. As an example, in structural biology, it allows to extract information about distance distributions on the nanometer scale via site-directed spin labeling. Conventional pulsed EPR of biological samples is currently limited to relatively large sample concentrations and cryogenic temperatures, mainly due to low sensitivity and the significant dead time associated with conventional resonator-based EPR setups, essentially precluding in-cell EPR under physiological conditions. This paper presents our latest progress toward single-cell pulsed EPR using VCO-based EPR-on-a-chip (EPRoC) sensors. Together with an analytical model for VCO-based pulsed EPR, we present an experimental scheme to perform dead-time-free pulsed EPR measurements using EPRoC detectors. The proposed scheme is validated using extensive numerical simulations and proof-of-concept experiments on the spin dynamics of an organic radical at room temperature using a custom-designed EPRoC detector operating in the Ka-band around 30.4 GHz. Additionally, we discuss methods to improve the excitation field homogeneity and sample handling through chip post-processing and custom-designed microfluidics. Finally, we present our progress towards compact, portable pulsed EPR spectrometers incorporating EPRoC detectors, microfluidics, and custom-designed permanent magnets. Such portable EPR spectrometers can pave the way toward new EPR applications, including point-of-care diagnostics.
{"title":"Towards single-cell pulsed EPR using VCO-based EPR-on-a-chip detectors","authors":"Mohamed Atef Hassan, M. Kern, Anh Chu, Gatik Kalra, E. Shabratova, Aleksei Tsarapkin, Neil MacKinnon, K. Lips, C. Teutloff, R. Bittl, J. Korvink, J. Anders","doi":"10.1515/freq-2022-0096","DOIUrl":"https://doi.org/10.1515/freq-2022-0096","url":null,"abstract":"Abstract Electron paramagnetic resonance (EPR) is the gold standard for studying paramagnetic species. As an example, in structural biology, it allows to extract information about distance distributions on the nanometer scale via site-directed spin labeling. Conventional pulsed EPR of biological samples is currently limited to relatively large sample concentrations and cryogenic temperatures, mainly due to low sensitivity and the significant dead time associated with conventional resonator-based EPR setups, essentially precluding in-cell EPR under physiological conditions. This paper presents our latest progress toward single-cell pulsed EPR using VCO-based EPR-on-a-chip (EPRoC) sensors. Together with an analytical model for VCO-based pulsed EPR, we present an experimental scheme to perform dead-time-free pulsed EPR measurements using EPRoC detectors. The proposed scheme is validated using extensive numerical simulations and proof-of-concept experiments on the spin dynamics of an organic radical at room temperature using a custom-designed EPRoC detector operating in the Ka-band around 30.4 GHz. Additionally, we discuss methods to improve the excitation field homogeneity and sample handling through chip post-processing and custom-designed microfluidics. Finally, we present our progress towards compact, portable pulsed EPR spectrometers incorporating EPRoC detectors, microfluidics, and custom-designed permanent magnets. Such portable EPR spectrometers can pave the way toward new EPR applications, including point-of-care diagnostics.","PeriodicalId":55143,"journal":{"name":"Frequenz","volume":"76 1","pages":"699 - 717"},"PeriodicalIF":1.1,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44773499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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