Estructures ressonants en forma de biga (p.e. ponts o palanques) són molt interessants com a element transductor en sensors físics, químics i biològics basats en sistemes micro-/nanoelectromecànics (M-/NEMS) degut a la seva simplicitat, al gran rang de dominis que poden sensar, i a la seva extremada alta sensibilitat. Aquesta tesis està focalitzada en el disseny, fabricació i caracterització de CMOS-MEMS monolítics basats en bigues ressonants a escala sub-micromètrica per a la seva utilització en la detecció ultra sensible de massa amb un dispositiu portable. Els ressonadors operen en mode dinàmic on la massa es mesurada com un canvi de la seva freqüència de ressonància que és induïda electrostàticament i llegida d'una forma capacitiva mitjançant un circuit CMOS integrat monolíticament. Dues aproximacions tecnològiques diferents són considerades per tal de fabricar bigues ressonants a escala sub-micromètrica sobre xips CMOS prèviament processats, possibilitant una integració monolítica: (i) post processant els xips CMOS amb tècniques de nano fabricació per obtenir les estructures ressonants o (ii) definint els ressonadors al mateix temps que els circuits CMOS. Per les dues aproximacions, es presenten dispositius de metall i de polysilici amb sensibilitats de massa sense precedents (per a sensors CMOS monolítics) dins el rang dels atto-/zeptograms. Es presenta una comparativa dels resultats aconseguits mitjançant les dues aproximacions tecnològiques.Es dissenyen circuits de lectura CMOS d'alta sensibilitat per amplificar el corrent capacitiu amb guanys de transimpedància (utilitzant una tecnologia comercial CMOS 0.35-μm) de fins a 120 dBΩ a 10 MHz possibilitant la detecció del desplaçament del ressonador amb resolucions de fins a ~10 fm/√Hz semblants a les obtingudes pels millors sistemes de detecció òptics reportats i sense la necessitat d'un equipament complexa. Es presenta la caracterització elèctrica, a l'aire i al buit, de dispositius CMOS-MEMS fabricats que corroboren la capacitat de l'aproximació monolítica presentada per mesurar la característica freqüencial de ressonadors a escala sub-micromètrica. S'aconsegueix una transducció electrostàtica òptima i es mesuren respostes freqüencials elèctriques amb pics elevats (fins a 20 dB o més) i grans canvis de fase (fins a 160º) al voltant de la freqüència de ressonància. També es reporten mesures on s'observen efectes de softening/harderning de la constant de molla i d'histèresis produïts per les no linealitats així com la detecció del moviment Brownià intrínsec demostrant el bon matching de soroll entre el ressonador i el circuit de lectura. També es presenten els resultats de calibració, de mesures en temps real, i d'anàlisi de la resolució dels dispositius fabricats obtenint valors de fins a ~30 zg/√Hz (equivalent a ~6 pg/cm2√Hz) en condicions de buit que indiquen la millora respecte a treballs anteriors en termes de sensibilitat, resolució i procés de fabricació.Es presenta i es testeja un circuit oscil·lador Pierce CMOS adaptat per a treballar amb ressonadors de ~10 MHz i amb resistències mecàniques equivalents de fins a 100 MΩ demostrant que és factible la detecció d'attograms amb un dispositiu sensor completament portable. / Resonant beams structures are very attractive transducers for physical, chemical and biological sensors based on micro-/nanoelectromechanical systems (M-/NEMS) due to its simplicity, wide range of sensing domains, and extremely high sensitivity. This Ph.D. thesis is focused on the design, fabrication and characterization of monolithic CMOS-MEMS based on sub-micrometer scale resonant beams for its application in ultrasensitive mass detection with a portable device. The resonators operate in dynamic mode where the mass is measured as a change of its resonant frequency which is electrostatically induced and capacitive readout by means of a monolithically integrated CMOS circuitry. Two different technological approaches are considered to fabricate sub-micrometer scale resonant beams on pre-processed CMOS chips allowing a monolithic integration: (i) nano post-processing of the CMOS chip to obtain the resonant beams or (ii) definition of the resonant beams at the same time that the CMOS circuits. From both approaches, metal and polysilicon devices exhibiting unprecedented mass sensitivities (for monolithic CMOS sensors) in the atto-/zeptogram range are reported. Comparison of the results following both approaches is given.High-sensitivity readout CMOS circuits are specifically designed to amplify the capacitive current with transimpedance gains (using a commercial 0.35-μm CMOS technology) up to 120 dBΩ at 10 MHz allowing to detect the resonator displacement with resolutions up to ~10 fm/√Hz which are similar than the best reported optical readout systems without the need of a bulky setup.Electrical characterization, in air and in vacuum conditions, of fabricated CMOS-MEMS devices is presented corroborating the ability of the presented monolithic approach in measuring the frequency characteristics of sub-micrometer scale beam resonators. Optimal electrostatic transduction is achieved measuring electrical frequency responses with high peaks (up to 20 dB or more) and large phase shifts (up to 160º) around the resonance frequency. Measurements showing soft/hard-spring effect and hysteretic performance due to nonlinearities are also reported as well as the detection of intrinsic Brownian motion demonstrating the noise-matching between the resonator and the readout circuit. Results from calibration, real time mass measurements, and resolution analysis on fabricated devices obtaining values down to ~30 zg/√Hz (equivalent to ~6 pg/cm2√Hz) in vacuum conditions are also reported indicating the improvement from previous works in terms of sensitivity, resolution, and fabrication process.A specific CMOS Pierce oscillator circuit adapted to work with ~10 MHz beam resonators showing motional resistance up to 100 MΩ is presented and tested demonstrating the feasible attogram detection with a completely portable sensor device.

The conventional medical immunoassays (ELISA/CLIA/FPIA) are not only costly (>10,000 USD), large in size (>10,000 cm3), but also require a vast number of sampling (25 £gL/well ¡Ñ 12 well) and long detection time (1~2.5 hr). To develop a biomedical microsensor for the application of portable detecting microsystem, this thesis proposes a flexural plate wave (FPW) microsensor with a novel reflection grating electrode (RGE) microstructure. Comparing to the conventional acoustic microsensors, the FPW based device has higher mass sensitivity, lower operation frequency but higher noise level. To overcome this disadvantages, this study added the RGE microstructure into the design of FPW sensor and investigated its influences on the reduction of insertion loss and noise level. By using the surface and bulk micromachining technologies, this thesis designed and fabricated FPW-based mass-sensing device with a small volume of 0.189 cm3 and a novel RGE microstructure. The main processing steps adopted in this research include six photolithoghaphies and nine thin-film depositions. In this work, a high figure-of-merit C-axial orientation ZnO piezoelectric thin-film was deposited by a commercial magnetic radio-frequency (RF) sputter system. On the other hand, the gold/chrome interdigital transducer (IDT) and RGE aluminum electrode were deposited utilizing a commercial E-beam evaporator system. For the optimization of design specifications of the FPW devices, the space of input and output IDTs, pair number of IDT, length of delay line gap and with/without RGE design were varied and investigated. Under the optimized IDT specification, the FPW microstructure presents lower central frequency (2¡ã4 MHz), insertion loss (-11 dB) and noise level (<-30 dB) than that of the FPW based microsensor without RGE microstructure. In addition, as the sampling volume of the testing DI water is equal to 1 £gL, a high mass sensitivity (-48.3 cm2/g) and short responding time (5 min) of the FPW microsensor with RGE design can be achieved in this work. The excellent characteristics mentioned above demonstrated the implemented FPW microsensor is very suitable for the applications of portable biomedical detecting microsystems.

There is a need to discover advanced materials to address the pressing challenges facing humanity, however there are far too many combinations of material composition and processing conditions to explore using conventional experimentation. One powerful approach for accelerating the rate at which materials are explored is by miniaturizing the scale at which experiments take place. Reducing the size of samples has been tremendously productive in biomedicine and drug discovery through standardized formats such as microwell plates, and while these formats may not be the most appropriate for studying polymeric materials, they do highlight the advantages of studying materials in ultra-miniaturized volumes. However, precise and controlled methods for handling diverse samples at the sub-femtoliter-scale have not been demonstrated. In this thesis, we establish that scanning probes can be used as a technique for realizing and interrogating sub-femtoliter scale polymer samples. To do this, we develop and apply methods for patterning materials with control over their size and composition and then use these methods to study material systems of interest. First, we develop a closed-loop method for patterning liquid samples using scanning probes by utilizing tipless cantilevers capable of holding a discrete liquid drop together with an inertial mass sensing scheme to measure the amount of liquid loaded on the probe. Using these innovations, we perform patterning with better than 1% mass accuracy on the pL-scale. While dispensing fluid with tipless cantilevers is successful for patterning pL-scale features and can be considered a candidate for robust nanoscale manipulation of liquids for high-throughput sample preparation, the minimum amount of liquid that can be transferred using this method is limited by number of factors. Thus, in the second section of this thesis, we explore ultrafast cantilevers that feature spherical tips and find them capable of patterning aL-scale features with in situ feedback. The development of methods of interrogating polymers at the pL-scale led us to explore how the mechanical properties of photocurable polymers depend on processing conditions. Specifically, we investigate the degree to which oxygen inhibits photocrosslinking during vat polymerization and how this effect influences the mechanical properties of the final material. We explore this through a series of macroscopic compression studies and AFM-based indentation studies of the cured polymers. Ultimately, the mechanical properties of these systems are compared to pL-scale features patterned using scanning probe lithography and we find that not only does oxygen prevent full crosslinking when it is present during the post-print curing, but the presence of oxygen during printing itself irreversibly softens the material. In addition to developing new methods for realizing ultra-miniaturized samples for study, the novel scanning probe methods in this work have led to new paradigms for rapidly evaluating complex interactions between material systems. In particular, we present a novel method to quantitatively investigate the interaction between the metal-organic frameworks (MOFs) and polymers by attaching a single MOF particle to a cantilever and studying the interaction force between this MOF and model polymer surfaces. Using this approach, we find direct evidence supporting the intercalation of polymer chains into the pores of MOFs. This work lays the foundation for directly characterizing the facet-specific interactions between MOFs and polymers in a high-throughput manner sufficient to fuel a data-driven accelerated material discovery pipeline. Collectively, the focus of this thesis is the development and utilization of novel scanning probe methods to collect data on extremely small systems and advance our understanding of important classes of materials. We expect this thesis to provide the foundation needed to transform scanning probe systems into instruments for performing reliable nanochemistry by combining controlled and quantitative sample preparation at the nanoscale and high-throughput characterization of materials. To conclude, we present an outlook about the necessary technological advancements and promising directions for materials innovations that stem from this work.