Cantilever arrays

X.L. Su and Y.B. D, Micromechanical cantilever array sensors for selective fungal immobilization and fast growth detection. Biosens. Bioelectron. 21, 840-856 (2005). 

Cantilevers are usually microfabricated from silicon by using conventional pho-tomasking and etching techniques. Typical dimensions of a cantilever are 100 pm in length, 20 pm in width, and 1 pm in thickness. Silicon and silicon nitride cantilevers and cantilever arrays that utilize optical beam deflection for signal transduction are commercially available. Piezoresistive cantilever arrays are also commercially available. Piezoresistive cantilevers are 120 pm in length, 1 pm in thickness, and 40 pm in width. 

Fig. 4.22 Schematic of cantilever operating in (a) resonant and (b) static bending mode, (c) Photograph of microfabricated cantilever array (adapted from Battiston et al., 2001, p. 122)...

Because of this great flexibility in the design, fabrication, and readout, cantilever arrays for gaseous (Kim et al., 2001) and biosensing aqueous applications (Arntz et al., 2003) have been realized. Needless to say, the issues of selectivity, dynamic range, response time, and so on depend ultimately on the interactions of the analyte with the selective layer. What cantilevers can offer is a low instrumental detection limit and the possibility of avoiding experimental artifacts due to the effects not related to the chemical interactions. Because they are relatively new, it is too early to estimate their usefulness. They will have to stand the test of time. 

Figure 10.13 Scanning electron microscope image of the cantilever array, fabricated by Nanoink Inc., used for the domain writing the insert shows an enlarged view of a single tip at the end of a cantilever.

Fig. 2. Scanning electron micrograph of a piezoresistive cantilever array.

This problem may be solved by using cantilever arrays where each cantilever element produces a unique response due to the chemically specific coatings used. The higher the uniqueness of an individual cantilever, the higher the specificity and the lower the number of cantilevers needed in an array. The design goal for the array is to move away from the y = x diagonal in the ROC curve toward the y-axis. 

R.G. Rudnitsky, E.M. Chow and T.W. Kenny, Rapid biochemical detection and differentiation with magnetic force microscope cantilever arrays. Sensors and Actuators A. Physical, 83 (2000) 256-262. 

Lange, D., Hagleitner, C., Hierlemann, A., Brand, O., and Baltes, H. (2002). Complementary metal oxide semiconductor cantilever arrays on a single chip Mass-sensitive detection of volatile organic compounds. Anal. Chem. 74,3084-3095. 

This system can be easily scaled up allowing the detection of different concentrations and/or different analytes simultaneously. For biological experiments, arrays of cantilevers are normally employed (5) as one cantilever can be used as reference. Then the expected biointeraction can be diferenciated from any change of the experimental conditions. Actually, there are several commercial platforms available, based on cantilever-array sensors. 

McKendry R, Zhang J, Arntz Y, et al. (2002). Multiple label-free biodetection and quantitative DNA-binding assays on a nanomechanical cantilever array. Proc. of the National Academy of Sciences. 99 9783-9788. 

Archibald, R., Datskos, R, Devault, G., Lamberti, V., Lavrik, N., Noid, D., Sepaniak, M., and Dutta, P. 2007. Independent component analysis of nanomechanical responses of cantilever arrays. Anal Chim Acta 584,101-105. 

Kim, S., Rahman, T., Senesac, L. R., Davison, B. H., and Thundat, T. 2009. Piezoresistive cantilever array sensor for consolidated bioprocess monitoring. Scanning 31,204-210. 

KeUing, S., Paoloni, R, Huang, J., Ostanin, V. R, and Elliott, S. R. 2009. Simultaneous readout of multiple micro cantilever arrays with phase-shifting interferometric microscopy. Rev Set Instrum 80, 093101. 

We have demonstrated an extremely sensitive sensor platform for groundwater monitoring. The sensitivity of the cantilever sensor depends on cantilever dimension, while the selectivity depends on die selectivity of the surface coating for chemical interactions. Research is underway to develop cantilever arrays for simultaneous multi-analyte detection. The primary advantages of the microcantilever method are (1) the sensitivity of microcantilevers based on their ability to detect cantilever motion with subnanometer precision (2) their ability to be fiibricated into multi-element sensor arrays and (3) their ability to work in a liquid environment. 

C.A. Mirkin, Y. Wang, L.R. Giam, and M. Park, Independently-addressable, self-correcting inking for cantilever arrays, US Patent 7954166, assigned to Northwestern University (Evanston, IL), May 31,2011. 

A. Bietsch, J. Zhang, M. Hegner, H.P. Lang, C. Gerber, Rapid Functionalization of Cantilever Array Sensors by Inkjet Printing. Nanotechnology (2004) vol 15 pp. 873-880. 

Fig. 28.4 Inkjet printing of individual droplets onto a cantilever array (a) as a scheme and (b) as seen by a video camera. A positioning system allows accurate placement of single droplets onto selected cantilevers. When deposited with a small pitch, the droplets merge into a continuous layer covering the entire cantilever length. For demonstration, three droplets of water are deposited onto selected cantilevers. Owing to the oblique view of the camera, only the central cantilever is in focus (Reprinted with permission from Bietsch et al. 2004, Copyright 2004 lOP)...

Bietsch A, Zhang J, Hegner M, Lang HP, Gerber C (2004) Rapid functionalization of cantilever array sensors by inkjet printing. Nanotechnology 15 873-880... 

Battison FM, Ramseyer J-P, Lang HP, BaUer MK, Gerber C, Gimzewski JK, Meyer E, Guntherodt H-J (2001) A chemical sensor based on a microfabricated cantilever array with simultaneous resonance-frequency and bending readout. Sens Actuators B 77 122-131... 

Bailer MK, Lang HP, Fritz J, Gerber C, Gimzewski JK, Drechsler U, Rothuizen H, Despont M, Vettiger PF, Battiston FM, Rtunseyer JP, Fomaro P, Meyer E, GUntherodt H J (2000) A cantilever array-based artificial nose. Ultramicroscopy 82 1-9... 

Lange D, Hagleitner C, Hierlemann A, Brand O, Baltes H (2002) Complementary metal oxide semiconductor cantilever arrays on a single chip mass-sensitive detection of volatile oigrmic compounds. Anal Chem 74 3084-3095 Lange U, Roznyatovskaya NV, Mirsky VM (2008) Conducting polymers in chemical sensors and arrays. Anal Chim Acta 614 1-26... 

Fig. 7.11 Views of commercially possible cantilevers (a) cantilever array wafer (b-d) single cantilever arrays (Uploaded from http //www.concenttis.ch and http //cantion.com)...

Injection molding, an economical mass production technique, has also been used to fabricate microcantilevers out of thermoplastic polymers (McFarland et al. 2004 McFarland and Colton 2005a, b). In this process, a molten polymer such as polypropylene is forced under pressure into a steel cavity (mold) the shape of the cavity defines the dimensions of both the base and the cantilever(s). Injection-molded microcantilevers have been shown to be of equal caUber to commercial silicon miCTOcantile-vers. McFarland et al. (2004) and McFarland and Colton (2005a, b) specified in detail the fabrication of injection-molded microcantilevers. Despite their advantages over silicon-based cantilever arrays, polymeric cantilever arrays are not commercially available. 

Boisen A, Thundat T (2009) Design and fabrication of cantilever array biosensors. Mater Today 12 32-38 Bracher PJ, Gupta M, Whitesides GM (2010) Patterning precipitates of reactions in paper. J Mater Chem 20 5117-5122 Briand D, Colin S, Gangadharaiah A, Vela E, Dubois P, Thiery L, de Rooij NF (2006) Micro-hotplates on polyimide for sensors and actuators. Sens Actuators A 132 317-324... 

Lang, H., Hegner, M., Gerber, C. Cantilever array sensors. Mater. Today 8(4), 30-36 (2005)... 

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