Buoyant Mass Research Articles

Hybrid particle-phase field model and renormalized surface tension in dilute suspensions of nanoparticles

We present a two-phase field model and a hybrid particle-phase field model to simulate dilute colloidal sedimentation and flotation near a liquid-gas interface (or fluid-fluid interface in general). Both models are coupled to the incompressible Stokes equation, which is solved numerically using a combination of sine and regular Fourier transforms to account for the no-slip boundary conditions at the boundaries. The continuum two-phase field model allows us to analytically solve the equilibrium interfacial profile using a perturbative approach, demonstrating excellent agreement with numerical simulations. Notably, we show that strong coupling to particle dynamics can significantly alter the liquid-gas interface, thereby modifying the liquid-gas interfacial tension. In particular, we show that the renormalized surface tension is monotonically decreasing with increasing colloidal particle concentration and decreasing buoyant mass. Published by the American Physical Society 2024

Influence of glacial influx on the hydrodynamics of Admiralty Bay, Antarctica - study based on combined hydrographic measurements and numerical modeling

This study investigates the impact of glacial water discharges on the hydrodynamics of a glacial bay in Antarctica, comparing it to well-studied northern hemisphere fjords. The research was carried out in Admiralty Bay (AB) in the South Shetland Islands, a wide bay adjacent to twenty marine-terminating glaciers. From December 2018 until February 2023, AB water properties were measured on 136 days. This dataset showed that a maximally two-layered stratification occurs in AB and that glacial water is always the most buoyant water mass. Using the Delft3D Flow, a three-dimensional hydrodynamical model of AB was developed. During tests, the vertical position and initial velocity of glacial discharges have been shown to be insignificant for the overall bay circulation. Fourteen model scenarios have been calculated with an increasing glacial influx added. The AB general circulation pattern consists of two cyclonic cells. Even in scenarios with significant glacial input, water level shifts and circulation are predominantly controlled by the ocean. Glacial freshwater is carried out of AB along its eastern boundary in a surface layer. Freshwater thickness in this outflow current is maximally 0.27-0.35 m. Within the inner AB inlets, significant glacial influx produces buoyancy-driven vertical circulation. Using an approach combining hydrographic and modeling data, a four-year timeseries of glacial influx volumes into AB has been produced. On average, glacial influx in summer is 10 times greater than in spring and winter and 3 times higher than in autumn. The annual glacial influx into AB was estimated at 0.434-0.632 Gt. Overall, the study demonstrated the unique characteristics of the topography and forcings that influence the hydrodynamics of an Antarctic glacial bay.

Global mass of buoyant marine plastics dominated by large long-lived debris

The fate of plastics that enter the ocean is a longstanding puzzle. Recent estimates of the oceanic input of plastic are one to two orders of magnitude larger than the amount measured floating at the surface. This discrepancy could be due to overestimation of input estimates, processes removing plastic from the surface ocean or fragmentation and degradation. Here we present a 3D global marine mass budget of buoyant plastics that resolves this discrepancy. We assimilate observational data from different marine reservoirs, including coastlines, the ocean surface, and the deep ocean, into a numerical model, considering particle sizes of 0.1–1,600.0 mm. We find that larger plastics (>25 mm) contribute to more than 95% of the initially buoyant marine plastic mass: 3,100 out of 3,200 kilotonnes for the year 2020. Our model estimates an ocean plastic input of about 500 kilotonnes per year, less than previous estimates. Together, our estimated total amount and annual input of buoyant marine plastic litter suggest there is no missing sink of marine plastic pollution. The results support higher residence times of plastics in the marine environment compared with previous model studies, in line with observational evidence. Long-lived plastic pollution in the world’s oceans, which our model suggests is continuing to increase, could negatively impact ecosystems without countermeasures and prevention strategies.

Theoretical analysis of unsteady buoyant turbulent heat and mass transport from a vertical plate using LRN k-ϵ model

The contemporary analysis has been developed to investigate the transient natural convective combined heat and mass transport of a turbulent flow adjacent to the plate by utilizing the low Reynolds number (LRN) k-ϵ model. The research problem on turbulent flow is assumed to be two dimensional and viscous incompressible. The governing turbulent equations such as continuity, momentum, energy, concentration, turbulent kinetic energy (TKE) and dissipation rate of TKE are considered as per the flow geometry. Due to the non-availability of analytical or direct numerical techniques, the corresponding highly nonlinear PDE’s are solved by adopting the standard implicit type of finite difference method namely Crank–Nicolson scheme. Also, this scheme is unconditionally stable and helps to keep the governing turbulent flow equations in discretized form and are solved via tridiagonal matrix algorithm. The simulated results for several control parameters including turbulent Reynolds number are graphically displayed and also analyzed the flow profiles. To understand the physical phenomenon of turbulent flow, the authors shown the turbulent behavior of average momentum, energy and mass transfer rates. It has been noted that, the average temperature and concentration fields boosted with rising values of . Also, TKE and dissipation rate of TKE profiles increase with enhancing turbulent values. In addition, the simulated turbulent flow results from the LRN k-ϵ model are compared with usual laminar flows as a special case and found to be in respectable agreement.

Response of a temperate coral to temperature stress: A comparison of populations across sites

The negative effects of warming temperatures on coral physiology are well-documented. However, research increasingly suggests that these effects are variable and that the degree to which corals are impacted by higher temperatures are dependent on a range of environmental and physiological variables. In tropical corals, which live near their upper thermal limits, these disparities have led to significant differences in bleaching and other negative health effects even over relatively small spatial scales. However, the response of temperate corals across small spatial scales is less well understood despite their occurrence in areas with larger temperature ranges than their tropical counterpart. To determine whether responses to thermal stress (27.4 versus 29 °C) differed in a common temperate coral species across a small geographic area, as has been documented in tropical corals, we evaluated coral growth and photosynthetic efficiency (Fv/Fm) of the coral Oculina arbuscula over the course of eight weeks when grown at differing temperatures. When measured as buoyant mass (calcification), growth of O. arbuscula did not differ as a function of temperature or site of collection. In contrast, when measured as change in tissue mass or total wet mass, elevated temperature suppressed growth. Change in total wet mass also varied significantly by collection site, corals from some sites experiencing little if any growth and those from other sites experiencing negative growth. Photosynthetic efficiency (Fv/Fm) was significantly lower at 29 °C than at 27.4 °C. Analyses of symbionts showed that sequence variants related to the genus Breviolum made up ∼98% of all Symbiondiniaceae across all sites and temperature treatments with one variant (100% sequence identity to Breviolum psygmophilum) being 91% of the total community. Only one Symbiodiniaceae, with a 99.28% sequence identity to Breviolum psygmophilum, differed significantly as a function of temperature. It also comprised only 1–3% of the community. Bacterial microbiome variance increased during our experiment, but there were no significant effects of temperature or collection site. For O. arbuscula from these collection sites, location did not impact the coral's ability to withstand the effects of temperature stress.

Cell Mass and Stiffness As Integrative Biomarkers of Cell State in Mantle Cell Lymphoma

Background: Mantle cell lymphoma (MCL) manifests extensive clinical phenotypic heterogeneity, ranging from indolent to aggressive, rapidly progressive disease. Molecular, genomic, transcriptomic, and immunophenotypic variation, as well as the presence of multiple subclones at diagnosis reflect the clinical diversity seen among MCL patients and make it challenging to define therapies that optimally align with individual patient risk. Biophysical phenotypes of cells, such as mass, density and stiffness, are valuable markers of changes in their intrinsic properties and closely associated with cellular states and functions, which have proven useful in elucidating fundamental processes in cell growth and development. We integrate single-cell biophysical features, which provide more granularity than canonical immunophenotypes, to further refine the biological characterization of MCL with the goal of defining rapid ex vivo biomarkers of clinical response or resistance. Methods: We utilize a device called suspended microchannel resonator (SMR) to perform biophysical measurements (mass, stiffness and density) of individual cells. We characterized the biophysical properties of MCL cells from representative sites, including peripheral blood, bone marrow and lymph nodes, of human clinical specimens and, additionally, spleen from six patient-derived xenografts (PDX) models of MCL. Furthermore, to identify genes that covary with lymphoma cell biophysical heterogeneity, we linked the biophysical measurements of individual MCL cells from the matched spleen, peripheral blood, bone marrow, and liver tissues of three carefully curated PDX models of MCL to downstream single-cell RNA-sequencing (SMR-scRNA-Seq). Results: We observed inter- and intra-tumor heterogeneity in mass and stiffness within each lymphoma specimen. Interestingly, these biophysical features reflect underlying histopathologic phenotypes, with higher mass and higher stiffness measured in blastoid and pleomorphic diseases as opposed to the smaller classical variant. By coupling biophysical measurement with transcriptomic profiling at single-cell resolution, we found that mass is strongly associated with the expression of genes annotated for cell division, cell cycle, and B-cell activation such as CCNB1, CDK1, CENPF, BLK, CD79A. Similarly, cell stiffness correlated with B-cell activation signatures and B-cell receptor signaling pathway activity, especially in the highly proliferative models. Functional genomics assays are ongoing to validate the contribution of these target pathways to MCL biophysical changes. To further define how B-cell activation impacts cellular biophysical properties, we profiled the biophysical properties of normal mature B-cell developmental stages from naïve B-cells to plasma cells. We found that cells at each differentiation stage possess a unique combination of mass, stiffness, and density. Highlighting the dynamic nature of these properties, B-cells undergo significant biophysical change after activation, with buoyant mass quadrupling upon activation and then rapidly decreasing by half. Preliminary data further reveal that mature B-cells lose approximately 25% of their stiffness after activation before reverting to their original stiffness after immunoglobulin class switching and even increasing in stiffness at the plasma cell stage. Most MCL cells are conventionally thought to derive from naïve pre-germinal center B cells, but our analysis revealed biophysical profiles overlapping strongly with more mature B cell states, suggesting that lymphomagenesis may entail reprogramming the machinery regulating cell mass and stiffness. We are now generating biophysical, transcriptomic, and genomic measurements within primary specimens from patients with MCL undergoing combined therapy targeting BTK, BCL2, and CD20 to assess their potential for inclusion within integrated predictive biomarkers. Conclusions: We established the biophysical landscape of MCL and non-malignant B-lymphoid cells to sharpen biological characterization and resolve tumor heterogeneity. We did so using a unique single-cell platform integrating transcriptomic and biophysical features as rapid, quantitative, and label-free measurements of live-cell state and phenotypic composition in pursuit of functionally integrated predictive biomarkers.

Measuring nanoparticles in liquid with attogram resolution using a microfabricated glass suspended microchannel resonator

The use of nanoparticles has been growing in various industrial fields, and concerns about their effects on health and the environment have been increasing. Hence, characterization techniques for nanoparticles are essential. Here, we present a silicon dioxide microfabricated suspended microchannel resonator (SMR) to measure the mass and concentration of nanoparticles in a liquid as they flow. We measured the mass detection limits of the device using laser Doppler vibrometry. This limit reached a minimum of 377 ag that correspond to a 34 nm diameter gold nanoparticle or a 243 nm diameter polystyrene particle, when sampled every 30 ms. We compared the fundamental limits of the measured data with an ideal noiseless measurement of the SMR. Finally, we measured the buoyant mass of gold nanoparticles in real-time as they flowed through the SMR.

Single-cell monitoring of dry mass and dry mass density reveals exocytosis of cellular dry contents in mitosis.

Cell mass and composition change with cell cycle progression. Our previous work characterized buoyant mass dynamics in mitosis (Miettinen et al., 2019), but how dry mass and cell composition change in mitosis has remained unclear. To better understand mitotic cell growth and compositional changes, we develop a single-cell approach for monitoring dry mass and the density of that dry mass every ~75 s with 1.3% and 0.3% measurement precision, respectively. We find that suspension grown mammalian cells lose dry mass and increase dry mass density following mitotic entry. These changes display large, non-genetic cell-to-cell variability, and the changes are reversed at metaphase-anaphase transition, after which dry mass continues accumulating. The change in dry mass density causes buoyant and dry mass to differ specifically in early mitosis, thus reconciling existing literature on mitotic cell growth. Mechanistically, cells in early mitosis increase lysosomal exocytosis, and inhibition of lysosomal exocytosis decreases the dry mass loss and dry mass density increase in mitosis. Overall, our work provides a new approach for monitoring single-cell dry mass and dry mass density, and reveals that mitosis is coupled to extensive exocytosis-mediated secretion of cellular contents.

A buoyant mass in the brain: Intraventricular migration of silicone oil

A buoyant mass in the brain: Intraventricular migration of silicone oil

Differentiating Live Versus Dead Gram-Positive and Gram-Negative Bacteria With and Without Oxidative Stress Using Buoyant Mass Measurements.

Expeditious and accurate determination of pathogenic bacteria cell viability is of great importance to public health for numerous areas including medical diagnostics, food safety, and environmental monitoring. In this work a cell buoyant mass classifier approach is presented to assess bacteria cell viability in real time. Buoyant mass measurements for live and dead Gram-positive and Gram-negative bacteria populations were acquired with a commercial suspended microchannel resonator, Archimedes, to generate receiver operating characteristic (ROC) curves. To quantitatively assess the difference in buoyant mass for live and dead bacteria populations, ROC curves were generated to demonstrate cell viability determination. The results are presented as a binary classifier with a decision boundary, above which cells are considered live and below which cells are considered dead. A decision threshold value is evaluated with consideration that a certain true positive rate (correct classification of a live cell) is maintained with an acceptable false positive rate. The potential for this approach to monitor cell viability in real time is significant, especially when considering multiple classifier dimensions such as buoyant mass and density. This classifier approach represents a next generation technique for rapid and label-free diagnostics based on cell feature measurements.

Cellular and biomolecular detection based on suspended microchannel resonators.

Suspended microchannel resonators (SMRs) have been developed to measure the buoyant mass of single micro-/nanoparticles and cells suspended in a liquid. They have significantly improved the mass resolution with the aid of vacuum packaging and also increased measurement throughput by fast resonance frequency tracking while target objects travel through the microchannel without stopping or even slowing down. Since their invention, various biological applications have been enabled, including simultaneous measurements of cell growth and cell cycle progression, and measurements of disease associated physicochemical change, to name a few. Extension and advancement towards other promising applications with SMRs are continuously ongoing by adding multiple functionalities or incorporating other complementary analytical metrologies. In this paper, we will thoroughly review the development history, basic and advanced operations, and key applications of SMRs to introduce them to researchers working in biological and biomedical sciences who mostly rely on classical and conventional methodologies. We will also provide future perspectives and projections for SMR technologies.

Gravity-induced phase phenomena in plate-rod colloidal mixtures

Gravity can affect colloidal suspensions since for micrometer-sized particles gravitational and thermal energies can be comparable over vertical length scales of a few millimeters. In mixtures, each species possesses a different buoyant mass, which can make experimental results counter-intuitive and difficult to interpret. Here, we revisit from a theoretical perspective iconic sedimentation-diffusion-equilibrium experiments on colloidal plate-rod mixtures by van der Kooij and Lekkerkerker. We reproduce their findings, including the observation of five different mesophases in a single cuvette. Using sedimentation path theory, we incorporate gravity into a microscopic theory for the bulk of a plate-rod mixture. We also show how to disentangle the effects of gravity from sedimentation experiments to obtain the bulk behavior and make predictions that can be experimentally tested. These include changes in the sequence by altering the sample height. We demonstrate that both buoyant mass ratio and sample height form control parameters to study bulk phase behavior.

Measuring dissolution profiles of single controlled-release drug pellets

Many solid-dose oral drug products are engineered to release their active ingredients into the body at a certain rate. Techniques for measuring the dissolution or degradation of a drug product in vitro play a crucial role in predicting how a drug product will perform in vivo. However, existing techniques are often labor-intensive, time-consuming, irreproducible, require specialized analytical equipment, and provide only “snapshots” of drug dissolution every few minutes. These limitations make it difficult for pharmaceutical companies to obtain full dissolution profiles for drug products in a variety of different conditions, as recommended by the US Food and Drug Administration. Additionally, for drug dosage forms containing multiple controlled-release pellets, particles, beads, granules, etc. in a single capsule or tablet, measurements of the dissolution of the entire multi-particle capsule or tablet are incapable of detecting pellet-to-pellet variations in controlled release behavior. In this work, we demonstrate a simple and fully-automated technique for obtaining dissolution profiles from single controlled-release pellets. We accomplished this by inverting the drug dissolution problem: instead of measuring the increase in the concentration of drug compounds in the solution during dissolution (as is commonly done), we monitor the decrease in the buoyant mass of the solid controlled-release pellet as it dissolves. We weigh single controlled-release pellets in fluid using a vibrating tube sensor, a piece of glass tubing bent into a tuning-fork shape and filled with any desired fluid. An electronic circuit keeps the glass tube vibrating at its resonance frequency, which is inversely proportional to the mass of the tube and its contents. When a pellet flows through the tube, the resonance frequency briefly changes by an amount that is inversely proportional to the buoyant mass of the pellet. By passing the pellet back-and-forth through the vibrating tube sensor, we can monitor its mass as it degrades or dissolves, with high temporal resolution (measurements every few seconds) and mass resolution (700 nanogram resolution). As a proof-of-concept, we used this technique to measure the single-pellet dissolution profiles of several commercial controlled-release proton pump inhibitors in simulated stomach and intestinal contents, as well as comparing name-brand and generic formulations of the same drug. In each case, vibrating tube sensor data revealed significantly different dissolution profiles for the different drugs, and in some cases our method also revealed differences between different pellets from the same drug product. By measuring any controlled-release pellets, particles, beads, or granules in any physiologically-relevant environment in a fully-automated fashion, this method can augment and potentially replace current dissolution tests and support product development and quality assurance in the pharmaceutical industry.

Mass measurements during lymphocytic leukemia cell polyploidization decouple cell cycle- and cell size-dependent growth

Cell size is believed to influence cell growth and metabolism. Consistently, several studies have revealed that large cells have lower mass accumulation rates per unit mass (i.e., growth efficiency) than intermediate-sized cells in the same population. Size-dependent growth is commonly attributed to transport limitations, such as increased diffusion timescales and decreased surface-to-volume ratio. However, separating cell size- and cell cycle-dependent growth is challenging. To address this, we monitored growth efficiency of pseudodiploid mouse lymphocytic leukemia cells during normal proliferation and polyploidization. This was enabled by the development of large-channel suspended microchannel resonators that allow us to monitor buoyant mass of single cells ranging from 40 pg (small pseudodiploid cell) to over 4,000 pg, with a resolution ranging from ∼1% to ∼0.05%. We find that cell growth efficiency increases, plateaus, and then decreases as cell cycle proceeds. This growth behavior repeats with every endomitotic cycle as cells grow into polyploidy. Overall, growth efficiency changes 33% throughout the cell cycle. In contrast, increasing cell mass by over 100-fold during polyploidization did not change growth efficiency, indicating exponential growth. Consistently, growth efficiency remained constant when cell cycle was arrested in G2 Thus, cell cycle is a primary determinant of growth efficiency. As growth remains exponential over large size scales, our work finds no evidence for transport limitations that would decrease growth efficiency.

Mechano-Optical Analysis of Single Cells with Transparent Microcapillary Resonators.

The study of biophysical properties of single cells is becoming increasingly relevant in cell biology and pathology. The measurement and tracking of magnitudes such as cell stiffness, morphology, and mass or refractive index have brought otherwise inaccessible knowledge about cell physiology, as well as innovative methods for high-throughput label-free cell classification. In this work, we present hollow resonator devices based on suspended glass microcapillaries for the simultaneous measurement of single-cell buoyant mass and reflectivity with a throughput of 300 cells/minute. In the experimental methodology presented here, both magnitudes are extracted from the devices' response to a single probe, a focused laser beam that enables simultaneous readout of changes in resonance frequency and reflected optical power of the devices as cells flow within them. Through its application to MCF-7 human breast adenocarcinoma cells and MCF-10A nontumorigenic cells, we demonstrate that this mechano-optical technique can successfully discriminate pathological from healthy cells of the same tissue type.

Does gas supersaturation by a chemical reaction produce bulk nanobubbles?

HypothesisSupersaturation of dissolved gas is the most commonly reported method for generating long-lived bulk nanobubbles. However, these reports are treated with skepticism because of the lack of techniques that directly show that these particles are gas filled bubbles. Therefore, this work has tested the hypothesis that supersaturation obtained by a chemical reaction produces long-lived nanosized bubbles in bulk using an established protocol that relies on evaluating the density of nanoparticles and measuring their response to external pressure. ExperimentsNanoparticles were generated using a chemical reaction between aqueous solutions of ammonium chloride and sodium nitrite. Standard nanoparticle sizing techniques, such as nanoparticle tracking analysis and dynamic light scattering, were utilized to determine the size and stability of the nanoparticles. Resonant mass measurement was used to measure the buoyant mass of the nanoparticles, and their compressibility was investigated by measuring their size under the application of external pressure. FindingsThe formation of nanoparticles was consistent with the kinetics of nitrogen gas evolution produced in the reaction, where the nanoparticle size was shown to be dependent on the pH and concentration of the reactants. However, the chemical reaction was found to generate incompressible nanoparticles with a density larger than that of the solvent, confirming that these particles were not gas-filled bubbles.

Relative Vibration of Suspended Particles With Respect to Microchannel Resonators and Its Effect on the Mass Measurement

In this work, the three-dimensional fluid–solid interaction vibration of particle in the oscillating resonator and its effect on the dynamic characteristics are analyzed and discussed. It demonstrates that the displacement of a particle is composed of two components, one is in phase with the acceleration of resonator and the other is out of phase. The former is responsible for the added mass effect and the latter results in a small damping. A modified measurement principle for detecting the buoyant mass is then presented by considering the in-phase component. The three-dimensional (3D) fluid–solid interaction problem involving the particle, fluid, and resonator is numerically solved, and the effects of density ratio, inverse Stokes number, and the ratio of channel height to particle diameter are studied. Based on the numerical results, a function characterizing the in-phase component is identified through a fitting procedure. According to the modified measurement principle and the analytical expression for the in-phase component, a calibration method is developed for measuring buoyant mass. Using this calibration method, the systematic measurement error induced by the vibration of particles can be effectively reduced.

Experimental verification of the steric-entropic mode of retention in centrifugal field-flow fractionation using illite clay plates

The commonly used theory to describe the normal Brownian mode of field-flow fractionation (FFF) assumes the particles to be point masses and hence the shape is ignored. Beckett and Giddings extended this theory to include the effect of thin rods and discs being forced very close to the accumulation wall. By including the decrease in the entropy this causes, they derived new expressions for the retention of such nonspherical particles in FFF. The steric-entropic theory predicts that when the sample cloud thickness is less than the major dimension of the rods or discs then particles elute earlier than predicted by the Brownian mode theory. This leads to an underestimation of the buoyant mass and equivalent spherical diameter calculated from FFF data. In this paper we report for the first time experimental data for the retention of thin illite particles in centrifugal FFF that agrees well with these steric-entropic predictions. Not only do the size distributions calculated using the Brownian mode theory shift to lower size when the field is increased but the shift in the retention ratio of the peak maxima of the FFF fractograms could be predicted fairly accurately by the steric-entropic equations.

Experimental investigation of the effect of natural convection on the evaporation characteristics of small fuel droplets at moderately elevated temperature and pressure

The role of natural convection in droplet evaporation is experimentally investigated for a range of micro-sized alkane fuel droplets at moderately elevated pressure and temperature. This paper assesses the impact of buoyant mass transfer from two perspectives; the resulting variation in steady-state evaporation rate, and the potential relation to non-linear temporal d2 profiles. The steady-state evaporation rate is found to increase linearly with initial droplet diameter at all tested conditions, where the relative improvement in evaporation rate depends upon the fuel type, pressure, and temperature. In addition to modifying the steady-state evaporation rate, the various environmental conditions also impact the occurrence and timing of d2 deviation, which manifests as a strong reduction in evaporation rate near the end of a droplet’s lifetime. Pressure tends to encourage the appearance of d2 deviation for both heptane and decane by increasing the proportion of evaporation for which natural convection is responsible. The effect of temperature depends upon the droplet volatility, and the results differ between the two test fuels. Overall, the relative importance of natural convection, as compared to pure molecular diffusion, appears to govern both the expected improvement in, and potential deviation from, steady-state evaporation. Proposed Grashof correlations justify the above hypothesis.

Linear and non-linear vibrations of fluid-filled hollow microcantilevers interacting with small particles

Linear and non-linear vibrations of a U-shaped hollow microcantilever beam filled with fluid and interacting with a small particle are investigated. The microfluidic device is assumed to be subjected to internal flowing fluid carrying a buoyant mass. The equations of motion are derived via extended Hamilton's principle and by using Euler-Bernoulli beam theory retaining geometric and inertial non-linearities. A reduced-order model is obtained applying Galerkin's method and solved by using a pseudo arc-length continuation and collocation scheme to perform bifurcation analysis and obtain frequency response curves. Direct time integration of the equations of motion has also been performed by using Adams-Moulton method to obtain time histories and analyze transient cantilever-particle interactions in depth. It is shown that exploiting near resonant non-linear behavior of the microcantilever could potentially yield enhanced sensor metrics. This is found to be due to the transitions that occur as a matter of particle movement near the saddle-node bifurcation points of the coupled system that lead to jumps between coexisting stable attractors.