| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Design of Flip-Chip Interconnect Using Epoxy-Based Underfill Up to V-Band Frequencies With Excellent Reliability
- 2010
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 58:8, s. 2244-2250
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This study demonstrates a flip-chip interconnect with epoxy-based underfill (epsilon(r) = 3.5 and tan delta = 0.02 at 10 MHz) for packaging applications up to V-band frequencies. To achieve the best interconnect performance, both the matching designs on GaAs chip and Al2O3 substrate were adopted with the underfill effects taken into consideration. The optimized flip-chip interconnect showed excellent performance from dc to 67 GHz with return loss below -20 dB and insertion loss less than 0.6 dB. Furthermore, the dielectric loss induced by the underfill was extracted from measurement and compared with the simulation results. The reliability tests including 85 degrees C/85 % relative humidity test, thermal cycling test, and shear force test were performed. For the first time, the S-parameters measurement was performed to check the flip-chip reliability, and no performance decay was observed after 1000 thermal cycles. Moreover, the mechanical strength was improved about 12 times after the underfill was applied. The results show that the proposed flip-chip architecture has excellent reliability and can be applied for commercial applications.
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| 3. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Fabrication process and 110 GHz measurement result of MS-to-CPW RF-via transition for RF-MEMS devices packaging applications
- 2009
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Ingår i: 2009 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2009. - 9781893580138
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Konferensbidrag (refereegranskat)abstract
- This paper presents the fabrication process of RF-via (0-level) and flip-chip bump (1-level) transitions for applications of packaging MS (microstrip) RF-MEMS devices. The interconnect structure with MS-to-CPW transition between GaAs MEMS substrate and Al2O3 motherboard was in-house fabricated. A novel fabrication process for RF-MEMS packaging is in detail. After fabrication, the samples were measured up to 110 GHz using on-wafer probing measurement. From the measured results, the insertion loss of entire interconnect structure is better than -2 dB up to 100 GHz, documenting the feasibility for millimeter-wave RF-MEMS devices packaging applications.
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| 4. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Flip-chip assembled 7 GHz ultra-low phase-noise InGaP HBT oscillator
- 2010
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Ingår i: 2010 International Conference on Compound Semiconductor Manufacturing Technology; Portland, OR; United States; 17 May 2010 through 20 May 2010. - 9781893580152
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Konferensbidrag (refereegranskat)abstract
- This paper reports on a flip-chip assembled 7 GHz ultra-low phase-noise GaAs InGaP heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) oscillator. The cross-coupled oscillator was flip-chip bonded to an in-house fabricated Al2O3 carrier with patterns optimized for low-loss transitions. After flip-chip, the phase noise of the crosscoupled InGaP HBT oscillator was improved due to an increased Q-factor of the resonant tank. An ultra-low phase-noise of -112 dBc/Hz @ 100 kHz offset and -128 dBc/Hz @ 1 MHz offset with a high output power of 7 dBm at 7 GHz was achieved. To our best knowledge, this is the lowest phase noise reported for a flip-chip assembled oscillator.
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| 5. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Flip-Chip-Based Multichip Module for Low Phase-Noise V -Band Frequency Generation
- 2010
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 58:9, s. 2408-2419
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper reports on a flip-chip (FC)-based multichip module (MCM) for low phase-noise (PN) V -band frequency generation. A high-performance x8 GaAs metamorphic high-electron mobility transistor monolithic microwave integrated circuit (MMIC) multiplier and a low PN 7-GHz GaAs InGaP heterojunction bipolar transistor (HBT) MMIC oscillator were used in the module. The microstrip MMICs were FC bonded to an Al2O3 carrier with patterns optimized for low-loss transitions. The FC-based module was experimentally characterized to have a PN of -88 dBe/Hz @ 100-kHz offset and -112 dBc/Hz @ 1-MHz offset with an output power of 11 dBm. For comparison, the MMICs were also FC bonded as individual chips and the performance was compared with the bare dies without FC bonding. It was verified that the FC bonding has no detrimental effect on the MMIC performance. The tests revealed that the FC module provided improved performance. To our best knowledge, this is the first FC-based module for millimeter-wave frequency generation. The module also presents one of the best PN reported for millimeter-wave frequency sources.
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| 6. |
- Hsu, Li-Han, 1981
(författare)
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Flip-Chip Interconnect for Millimeter-Wave Packaging Applications
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, with the demands for wireless communication systems increas rapidly, the operating frequency for the portable wireless is moving toward millimeter-waves. Millimeter-wave wireless communication systems require not only suitable functional IC components but also competent package with low cost and good interconnect performance. To meet the demands for commercial applications, package with low power consumption, low cost, small size, and light weight becomes indispensable. However, unlike low frequency applications, millimeter-wave frequencies introduce significant parasitics and therefore the interconnect between IC chips and packaging carriers must be carefully managed in order to maintain good electrical performance. Conventional bond-wire induces significant parasitic inductance and thus results in unwanted effects, which could deviate the IC performance after assembly, especially at millimeter-wave frequencies.Flip-chip interconnect has drawn lots of attentions for chip-level packaging at millimeter-wave frequencies due to several advantages over bond-wire, e.g., shorter interconnect length, smaller package size and higher throughput. However, at MMW frequency range, the proximity effect, or detuning effect, is a crucial issue for flip-chip due to the proximity of chip to substrate. The proximity effect may cause the flipped-chips to deviate from its original performance. Approaches like increasing the bump height, reducing the metal overlap and employing compensation design at the transition region have been proposed to improve flip-chip performance. In addition, flip- chip reliability is very crucial for industrial applications since it relies only on several metallic connections. Using underfill as a buffer layer between chips and carriers can significantly improve flip-chip reliability, but unfortunately, the trade-off is underfill-induced performance decay and deviation. Furthermore, cost-reduction is also very important for commercialization. Conventional ceramic-based carrier offers excellent chemical and physical properties but with higher cost. Using low-cost organic board might be a good solution to get lower cost with fair performance. However, the investigation for flip-chip on organic board is generally insufficient.This dissertation covers an overall study for flip-chip interconnect for millimeter-wave frequencies. It can be divided into two parts. The first part is about active device packaging. Single MMIC chips and mm-wave modules were flip-chip assembled for demonstration. A V-band SPDT switch for half-duplex RF front-end switching was flip-chip assembled and RF characterized to 67 GHz. By adopting hi-compensation design, the packaged switch showed excellent frequency response and very low additional loss.Moreover, a V-band frequency source with a 7 GHz oscillator and a x8 multiplier was flip-chip assembled onto a multi-chip carrier. For comparison, both the oscillator and x8 multiplier were also bonded as individual chips. From the measurement results, the flip-chip technique did not have any detrimental effects and the assembled module showed excellent phase noise of -112 dBc/Hz @ 1 MHz offset with high output power of 11 dBm, demonstrating outstanding performance for millimeter-wave frequency generation.The second part is about material investigation in a flip-chip system. Underfill is generally required for improving flip-chip reliability. However, underfill in a flip-chip interconnect might introduce negative effects i.e., chip impedance mismatch and dielectric loss at millimeter-wave frequencies. To investigate and solve this issue, an epoxy-based was applied to a flip-chip structure and measured up to 67 GHz. By using pre-matching design and low-loss underfill, the flip-chip assembly exhibited excellent performances with return loss below -20 dB and insertion loss less than 0.6 dB. In addition, the reliability test revealed that the flip-chip assembly also performed excellent reliability. The other material investigation is about flip-chip carrier material. Low-cost Rogers RO3210TM organic laminate was employed to replace ceramic-based carrier for cost reduction and performance improvement. Both passive transmission lines and active discrete mHEMTs were flip-chip bonded onto RO3210TM. The test results showed that RO3210TM is a promising packaging carrier for commercial applications up to 50 GHz.
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| 7. |
- Hsu, Peng-Hao, et al.
(författare)
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Highly responsive and rapid hydrogen peroxide-triggered degradation of polycaprolactone nanoparticles
- 2020
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Ingår i: Biomaterials Science. - : Royal Society of Chemistry (RSC). - 2047-4849 .- 2047-4830. ; 8:9, s. 2394-2397
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Tidskriftsartikel (refereegranskat)abstract
- We synthesized an oxidation-responsive polycaprolactone (O-PCL) bearing pendant arylboronic esters as H2O2-responsive motifs. H2O2 induces fast depolymerization of O-PCL within days. Nanoparticles formulated from O-PCL disintegrate and release payload in response to concentrations of H2O2 (50 mu M) that are relevant to human disease.
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| 8. |
- Naren, Gaowa, 1990, et al.
(författare)
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An all-photonic full color RGB system based on molecular photoswitches
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- On-command changes in the emission color of functional materials is a sought-after property in many contexts. Of particular interest are systems using light as the external trigger to induce the color changes. Here we report on a tri-component cocktail consisting of a fluorescent donor molecule and two photochromic acceptor molecules encapsulated in polymer micelles and we show that the color of the emitted fluorescence can be continuously changed from blue-to-green and from blue-to-red upon selective light-induced isomerization of the photochromic acceptors to the fluorescent forms. Interestingly, isomerization of both acceptors to different degrees allows for the generation of all emission colors within the red-green-blue (RGB) color system. The function relies on orthogonally controlled FRET reactions between the blue emitting donor and the green and red emitting acceptors, respectively.
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