There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Nanotechnology and biosensors

Pull-in instability as an inherently nonlinear and crucial effect continues to become increasingly important for the design of electrostatic MEMS and NEMS devices and ever more interesting scientifically. This review reports not only the overview of the pull-in phenomenon in electrostatically actuated MEMS and NEMS devices, but also the physical principles that have enabled fundamental insights into the pull-in instability as well as pull-in induced failures. Pull-in governing equations and conditions to characterize and predict the static, dynamic and resonant pull-in behaviors are summarized. Specifically, we have described and discussed on various state-of-the-art approaches for extending the travel range, controlling the pull-in instability and further enhancing the performance of MEMS and NEMS devices with electrostatic actuation and sensing. A number of recent activities and achievements methods for control of torsional electrostatic micromirrors are introduced. The on-going development in pull-in applications that are being used to develop a fundamental understanding of pull-in instability from negative to positive influences is included and highlighted. Future research trends and challenges are further outlined.

Electrostatic pull-in instability in MEMS/NEMS: A review

Textbook of biochemistry with clinical correlations , 4th edn TM Devlin, ed pp xvii + 1186, illustrated Wiley-Liss, New York, 1997 £2995, hardback

This beautifully illustrated and well-written book, with an impressive array of authors, is aimed at both undergraduate and postgraduate level As the editor states in the preface, it is not intended to be a compendium of biochemistry but rather emphasises the biochemistry of mammalian cells The first 22 chapters cover …

Textbook of biochemistry with clinical correlations

https://jcp.bmj.com/content/jclinpath/12/2/193.1.full.pdf

Practical Clinical Biochemistry

We report fabrication of potentiometric biosensors with silicon for the estimation of triglycerides and urea based on enzymatic reactions. The sensor is an Electrolyte–InsulatorSemiconductor capacitor (EISCAP) that shows a shift in the measured CV with changes in the pH of the electrolyte. Enzyme mediated biological reactions involve changes in the pH of the electrolyte and an EISCAP can be effectively used for detection of biological compounds. Optimization of the conditions for the enzymatic reaction and calibration of the sensor are included. Effect of replacing silicon with porous silicon is discussed.

Potentiometric biosensors based on silicon and porous silicon

In a surface micromachined cantilever the beam thickness, width and the gap get modified during fabrication. Since
performance of sensors and actuators strongly depend on the final geometry, it is essential to measure these parameters.
Electrical measurements have several advantages over microscopy and we present here two different electrical
techniques to measure undercut due to etching. In the resistance based approach, two polysilicon resistors of different
length and width are used and the undercut is extracted from the ratio of the measured resistances. In the second
technique, resonance frequency is measured for two sets of oxide anchored polysilicon cantilever beams with 20 and 30
µm widths. For a given length, the ratio between the measured frequencies for the two widths gives the value of
undercut. Measurements are done on both wet and dry etched polysilicon.

Electrical measurement of undercut in surface micromachining

Polysilicon layers deposited by Low Pressure Chemical Vapour Deposition (LPCVD) on sacrificial oxides are used for surface micromachined structures. Stiction is a major problem in surface micromachining both during processing and in use. Contact angle measurements on surfaces can give indication on the adhesivitiy of the surface. In this paper, contact angle measurements on polysilicon surface after different treatments are reported with a view to understand their stiction behavior. We also report on surface roughness measurements on these samples.

Contact angle measurements on polysilicon for surface micromachining applications

Suspended Gate Field Effect Transistor (SGFET) with lower subthreshold swing (S) can overcome high power dissipation during switching events. An electrostatic actuator, which is the fundamental building block of SGFET is fabricated using surface micromachining technique. Using a series feedback capacitor, the actuator was stabilized beyond the pull-in instability limit. The presence of negative differential capacitance is demonstrated by the voltage amplification method, which reduces the body factor (m) value less than 1.

Enakshi Bhattacharya

Papers

Potentiometric biosensors based on silicon and porous silicon

Electrical measurement of undercut in surface micromachining

Contact angle measurements on polysilicon for surface micromachining applications

Experimental demonstration of negative differential capacitance in a voltage controlled electrostatic actuator

Space charge limited currents and the statistical shift in amorphous semiconductors